Next Article in Journal
Seaweed Proteins: A Step towards Sustainability?
Previous Article in Journal
Ser9p-GSK3β Modulation Contributes to the Protective Effects of Vitamin C in Neuroinflammation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nutrients
Volume 16
Issue 8
10.3390/nu16081122
nutrients-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study

by
David M. Goldman
1,2,*,
Cassandra B. Warbeck
3 and
Micaela C. Karlsen
4,5
1
Department of Public Health, University of Helsinki, 00014 Helsinki, Finland
2
Department of Research and Development, Metabite Inc., New York, NY 10036, USA
3
Department of Family Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada
4
Department of Research, American College of Lifestyle Medicine, Chesterfield, MO 63006, USA
5
Departments of Applied Nutrition and Global Public Health, Adjunct Faculty, University of New England, Biddeford, ME 04005, USA
*
Author to whom correspondence should be addressed.
Nutrients 2024, 16(8), 1122; https://doi.org/10.3390/nu16081122
Submission received: 3 March 2024 / Revised: 28 March 2024 / Accepted: 8 April 2024 / Published: 10 April 2024
(This article belongs to the Collection Plant-Based Diets in Sports Nutrition and Performance)
Browse Figures
Versions Notes

Abstract

:
Despite increasing awareness of plant-based diets for health and athletic performance, athletes are cautioned that careful dietary monitoring is necessary. Whether commonly consumed plant-based diets are nutritionally adequate for maximal muscular hypertrophy remains unknown. This modeling study assessed the nutrient composition of completely plant-based diets scaled to the caloric demands of maximal muscle mass and strength development in adult male bodybuilders. To model calorie requirements, anthropometric data from bodybuilders were input into the Tinsley resting metabolic rate prediction equation, and an appropriate physical activity factor and calorie surplus were applied. Dietary data from a large cohort following completely plant-based diets were then scaled to meet these needs. Modeled intakes for nutrients of interest were calculated as 1.8 g/kg/day of protein and 2.75 g/meal of leucine, which surpass mean requirements for maximal increases in muscle mass and strength and muscle protein synthesis, respectively. Daily levels for all micronutrients, except vitamin D, also exceeded requirements. Saturated fat levels were aligned with dietary guidelines, although sodium levels exceeded recommended limits. Consumption of larger portions of commonplace plant-based diets, scaled to meet the energy demands of maximal accrual of muscle mass and strength, satisfied protein and leucine requirements without the need for additional planning.

Graphical Abstract

1. Introduction

A key motivation that drives the exercise habits of young men in the United States is muscle growth [1]. More than one quarter of this demographic pursues this goal, frequently engaging in muscle-enhancing behaviors including lifting weights, eating more food, and eating specific foods [2]. The position of the International Society of Sports Nutrition (ISSN) recommends animal-based protein sources for muscular hypertrophy [3], and this is reflected in the dietary habits of individuals undertaking resistance exercise training (RET) [4,5,6,7]. Poultry, dairy, eggs, and protein supplements constitute the main sources of protein in the diets of typical strength training gym users, and legumes may only be consumed rarely in this population [4]. Bodybuilders also consume large quantities of dietary protein [8], sourced mainly from meat and eggs [5,6,7]. Animal-based protein-rich foods and supplements may displace key nutrient-rich foods in these dietary patterns, where insufficient intake of fruits and vegetables has been reported in nearly half of gym users [9]. This contrasts with national public health recommendations that young men should decrease their intake of red and processed meat and include more fruits, vegetables, and whole grains in their diets [10] and international guidance to reduce meat intake and increase plant food [11,12]. There appears to be a disconnect between dietary recommendations for the amelioration of chronic diseases and increased muscular development, suggesting an either/or choice of long-term health or athletic pursuits.
At the same time, public awareness of plant-based diets for health and athletic performance has increased in recent years [13,14]. Plant-based diets encompass an array of dietary patterns that emphasize fruits, vegetables, whole grains, legumes, nuts, seeds, and plant products and may limit or exclude animal-derived products [15]. The term “completely plant-based diet” is applied in this study to describe diets that consist mainly of whole plant foods, reflected by fiber intakes that meet or exceed recommendations, and are devoid of animal products. Similar dietary patterns that have been previously studied use a variety of terminology, including vegan [16], “strict vegetarian” in the 7th Day Adventist Health Study [17], and whole food, plant-based [18]. The Academy of Nutrition and Dietetics has determined that plant-based diets, including vegetarian and vegan diets, are appropriate for athletes [19]. However, plant-based dietary patterns have historically been considered substandard for athletic performance and muscular development [20,21,22], with the primary reason being inadequate protein content [20,21,23,24,25,26]. Total protein intake is generally lower in people following plant-based diets compared to omnivorous diets [27], and plant proteins typically contain lower amounts of the amino acids (AAs) lysine, methionine, and leucine than animal-sourced proteins [28]. However, it is relevant to note that protein intakes generally exceed recommendations, regardless of diet type [27].
Leucine serves as both a building block for muscle protein synthesis (MPS) and a signaling molecule initiating MPS [29]. It has been determined that leucine is the most potent AA for stimulating MPS [30,31], which is the major driving force for nutrient-induced anabolism, processes involved in the creation of new bodily substances, cells, and tissues [32]. Caution, as well as careful planning and monitoring, has therefore been recommended to ensure that athletes following plant-based diets meet protein and amino acid needs [15,21,33,34,35,36]. Studies of aerobically or anaerobically trained adults who engage in recreational or competitive sports do not indicate inadequate intakes of total protein, lysine, methionine, leucine, key micronutrients, or lower diet quality, in individuals who follow plant-based diets compared to omnivorous diets [37,38,39,40,41,42]. However, these reports included subjects who consumed large quantities of protein supplements, obfuscating an evaluation of whether completely plant-based diets as commonly consumed (without emphasis on protein supplements) would satisfy the elevated protein required for maximal RET-induced gains in muscle mass and strength [43].
To the authors’ knowledge, the prevalence of plant-based dietary adherence in strength-sport athletes and those pursuing maximal muscle mass, such as bodybuilders, has not been reported. Bodybuilders are unique among strength-sport athletes in that the pursuit of muscle hypertrophy is the primary aim of RET, rather than a secondary consequence of strength and power development training [44]. The nutritional adequacy of completely plant-based diets followed by bodybuilders has been described [40], but plant-based diets prescribed for muscular hypertrophy frequently rely on protein supplements to maximize the anabolic response to RET [38,42]. It remains uncertain whether individuals who engage in RET and follow completely plant-based diets composed largely of whole foods that meet hypercaloric intake levels recommended to maximize muscle mass accrual (i.e., “bulking”) need to carefully plan and monitor their diets to meet protein, leucine, and micronutrient requirements.
For this modeling analysis, the nutrient needs of competitive bodybuilders were chosen because their professional success depends predominantly on their ability to maximize skeletal muscle mass [45,46]. Male bodybuilders were selected as the population of interest because female bodybuilders typically require less total protein intake due to their lower mean body mass [47,48]. There is a common belief that athletes and other individuals pursuing increased muscle mass while following plant-based diets require protein supplementation [49,50,51]. This modeling analysis aims to assess the validity of this perception. The objective of this modeling study is to determine whether commonplace, completely plant-based diets, scaled to meet the caloric needs of RET and muscular hypertrophy, provide sufficient protein and leucine to maximize muscle mass and strength while meeting micronutrient needs in male bodybuilders.

2. Materials and Methods

The estimated energy needs of competitive bodybuilders were calculated using data from a recent systematic review by Bauer et al. (2023) [48]. This systematic review included 16 studies that reported anthropometric data from 235 healthy male competitive bodybuilders with previous competition experience or currently in preparation for their first competition and who were not seeking weight loss [48]. The age range of these athletes was 22 to 35 years. Body mass and height ranged from 75 to 94 kg and 166 to 192 cm, respectively. Body fat levels were 5.8–10.7%. Weekly or monthly training durations, frequencies, and volumes were not described. However, other research has found that most competitive male bodybuilders completed 4–7 resistance training sessions per week, each lasting 60–90 min [52,53]. Off-season training sessions typically targeted 2–3 muscle groups, implemented 2–3 different exercises per muscle group, and included 3–4 sets per exercise. Sets were typically completed at intensities of 7–12 repetition maximum, and recovery between sets lasted 61–180 s. As shown in Table 1, median values were used for subsequent modeling calculations.
The Adventist Health Study-2 (AHS-2) cohort study was selected to provide dietary data for our model because it included the largest sample following a vegan diet (n = 5694) reported in the scientific literature [17]. In this study, the nutrient profiles of 71,751 subjects from AHS-2 were determined through a 204-item food frequency questionnaire (FFQ), which had been validated against 24 h recall data, and nutrition data were analyzed using a database containing over 20,000 foods [17]. Participants who reported consuming red meat, poultry, fish, eggs, milk, and dairy products not at all or less than once per month were classified as following strict vegetarian (vegan) diets. The mean fiber intake in this population was 46.7 g/day, which meets current guidelines [10] and thus satisfies our criteria for classification as a completely plant-based diet.
Energy requirements for maximal muscular hypertrophy can be calculated as total daily energy expenditure (TDEE) plus an energy surplus due to the whole-body anabolic response to overfeeding [54,55]. TDEE is comprised of the resting metabolic rate (RMR), which is the amount of energy required to maintain basic body functions, along with the appropriate physical activity level (PAL) factor [56]. RMR is calculated using body weight, age, and sex. Based on a recent meta-analysis evaluating the accuracy of RMR prediction equations in athletes [56], a newly developed RMR prediction equation was determined to be most accurate in male bodybuilders [57]. This formula, which is shown in Equations (1)–(3), was therefore used to calculate the predicted mean TDEE for the modeled sample.
Equations used to calculate energy requirements for male bodybuilders [54,55,57].
RMR (kcal/day) = 24.8 × Weight (kg) + 10
ES (kcal/day) = RMR × PAL × 0.15
EER (kcal/day) = RMR × PAL + ES (kcal/day)
EER: estimated energy requirements; ES: energy surplus; kcal: kilocalories; kg: kilograms; PAL: physical activity level; RMR: resting metabolic rate.
The determination of PAL was also necessary to calculate TDEE. During the off-season, or bulking phase, competitive male bodybuilders report engaging in four to seven days of RET per week, with session duration most commonly 60 to 90 min, in addition to one to four aerobic exercise sessions lasting 10 to 30 min [52]. This is reflective of a PAL of 1.75 (1.60–1.89), which is classified as “active” and describes athletes who exercise for approximately one hour per day [58]. Accordingly, a PAL of 1.75 was selected for calculations. It is worth noting that most bodybuilders reported completing twelve or more sets of exercise per muscle group per week [52]. This corresponds to a high training volume that has been established to stimulate maximal increases in muscle mass [59].
An energy surplus (ES) is recommended to achieve maximal hypertrophy because hypercaloric conditions potentiate muscle growth by supporting the increasing energy demands of progressively increasing RET volume [54,55]. A surplus of 10–20% of calories above maintenance needs has been recommended for more advanced trainees [55], the mean of which (15%) was used for calculations, as shown in Equations (1)–(3).
The determination of the protein intake level required to maximize RET-induced gains in muscle mass was based on a consensus statement from the International Olympic Committee (IOC) [60], which recommends protein intake for high-performance athletes pursuing maximal muscular hypertrophy and strength of 1.6 g/kg/day [47]. Daily protein intakes of 1.6 g/kg were therefore used for calculations. The mean protein intake in AHS-2 for subjects following a vegan diet was 14.5% of total calories [17]. EER were therefore multiplied by 0.145 to determine the mean calories from protein. This value was divided by four to calculate the mean total grams of protein.
To maximally trigger MPS, ISSN recommends leucine intakes as high as 3 g/meal [3], but other research suggests that this upper limit may be excessive [23]. Rather, dietary supplements containing 1.8 g of leucine appear to maximally stimulate MPS in young men and women [61,62]. When leucine content reaches or exceeds 2 g, as occurs with large protein doses, animal- and plant-based proteins exert similar anabolic effects [63,64,65]. We therefore set the threshold for effective leucine intake at 2 g per meal. It has been recommended that off-season bodybuilders consume 3–6 meals per day [66], and a simple solution for meeting protein and amino acid needs has been made to consume four protein-rich meals per day [67], one every three to four hours, to optimize MPS [68]. Consuming 2 g of leucine at each of four daily meals, for a total of ≥8 g per day of leucine, was therefore used as the target threshold for this modeling study. Leucine has been shown to constitute 8.8 ± 0.7% of animal-based proteins and 7.1 ± 0.8% of plant-based proteins [69], and dietary leucine content was calculated as 7.1% of total protein intake.
Target intake levels of saturated fat, ω3 polyunsaturated fatty acids (PUFA), linoleic acid, fiber, vitamin A, vitamin B6, folate, vitamin B12, vitamin C, vitamin D, vitamin E, calcium, iron, magnesium, phosphorus, potassium, sodium, and zinc were based on the Dietary Reference Intakes (DRIs) [70]. DRIs are nutrient reference values for vitamins and minerals intended to optimize health and prevent disease [71]. When available, Recommended Dietary Allowances (RDAs) were used. When unavailable, Adequate Intakes (AIs) were used. The sodium target intake level was based on the Chronic Disease Risk Reduction (CDRR) level [10]. Values pertaining to adult males aged 19–30 were selected for comparison with modeled intake levels in scaled plant-based diets.

3. Results

3.1. Energy Requirements

The estimated energy requirements were calculated, and the results are shown in Table 2.

3.2. Protein Requirements and Levels

Total daily protein requirements were calculated to be 135 g/day, as shown in Table 3. Total protein levels were calculated to be 151 g/day. Relative protein intake levels were then calculated to be 1.8 g/kg/day.
Total protein intake and protein intake levels relative to body mass exceeded target thresholds, as shown in Figure 1.

3.3. Leucine Levels

Leucine levels were calculated on a daily and per-meal basis, as shown in Equations (4) and (5). Both total daily leucine levels and leucine levels per meal exceeded target thresholds, as displayed in Figure 1.
Calculated leucine levels for male bodybuilders adhering to completely plant-based diets during the bulking phase.
Total leucine levels (11 g/day) = Total protein levels (151 g/day) × 7.1%
Leucine per meal (2.75 g) = Total protein levels (11 g/day)/4 meals
g: grams.

3.4. Micronutrient and Other Key Nutrient Levels

Average micronutrient intakes per 2000 kcal/day reported in the AHS-2 dataset [17] were scaled proportionately to 4239 kcal/day diets (Table 4). These values were directly compared to established DRIs for saturated fat, ω3 PUFA, linoleic acid, fiber, vitamin A, vitamin B6, folate, vitamin B12, vitamin C, vitamin D, vitamin E, calcium, iron, magnesium, phosphorus, potassium, sodium, and zinc [10]. All projected mean micronutrient levels met recommendations with the exceptions of vitamin D and sodium, as shown in Table 4. Projected mean vitamin D levels were slightly lower than the RDA (536 vs. 600 IU/day), and projected mean sodium levels exceeded the established CDRR level (7484 vs. 2300 mg/day). The projected mean saturated fat levels (5% of total calories) were below the established limits of 10% of total calories [10].

4. Discussion

This study assessed the adequacy of completely plant-based diets, tailored to the caloric demands of maximal skeletal muscle hypertrophy and strength development, in providing requisite amounts of protein, leucine, and essential micronutrients to adult male bodybuilders engaged in RET. Our findings substantiate that scaled plant-based diets satisfy protein requirements for maximizing RET-induced gains in muscle mass and strength. These diets also meet leucine thresholds and micronutrient adequacy, with the exception of vitamin D, for maximal stimulation of MPS and health requirements, respectively.
The daily energy requirements we calculated were larger than estimates in the existing literature. We calculated the calorie requirements for male bodybuilders to be 4239 kcal/day in the bulking phase based on the actual median age and body mass reported for these samples. This estimate exceeds findings from a systematic review of dietary intake studies in competitive bodybuilders following omnivorous diets that reported an average energy intake of 3821 kcal/day [8]. However, the dietary assessment methods used in these studies, which consisted mainly of 3- to 7-day food diaries, are known to underestimate energy intake [73]. Moreover, a recent cross-sectional study by Amatori and colleagues (2023) reported a mean calorie intake of 2632 kcal/day among bodybuilders following completely plant-based diets [40]. This study estimated food intake using a digital food diary, which may also underestimate energy intake [73]. This discrepancy may also be partially explained by differences in sex and body mass, which are variables within RMR equations that directly affect estimations [58]. Our modeling was performed using an entirely male population with a median body mass of 84.5 kg. Subjects in the studies by Spendlove (2015) and Amatori (2023) included 84% and 61% male subjects, and mean body masses were 83.7 kg and 72.3 kg in these samples, respectively [8,40]. The former reported mean body mass for men and women separately, and the latter reported mean body mass for men and women combined, which may have contributed to the divergent body masses and energy intakes reported in these studies.
The protein recommendations used in this study align with recommendations for maximal muscular development in young, healthy adults [43]. They align with existing guidelines for athletes following plant-based diets [74] and corroborate evidence that athletes undertaking RET while following completely plant-based diets meet protein requirements for maximal gains in muscle mass and strength [40,75,76]. Our study calculated protein intakes of 1.8 g/kg/day, which exceeds the mean intake levels of 1.6 g/kg/day required to maximize RET-induced gains in muscle mass and strength in healthy adults [47]. Protein intake levels were lower than those reported in a cross-sectional study by Amatori et al. (2023), which found that competitive bodybuilders adhering to completely plant-based diets consumed an average of 2.2 g/kg/day of protein derived from whole foods and supplements during the bulking phase [40]. Case reports have also indicated that well-trained bodybuilding and powerlifting subjects following plant-based diets achieved protein intakes ranging from 2.0–3.5 g/kg/day through a combination of whole foods and supplements [75,76]. Protein supplementation may explain the larger intakes reported in these studies as compared to the data analyzed by Rizzo et al. (2013) from the AHS-2 cohort [17], which included limited capture of some protein supplements or meal replacement shakes [77]. The top reported sources of dietary protein in this cohort among those following a vegan diet were whole plant foods such as legumes and grains [77]. However, the majority of research pertaining to protein intake for muscle protein remodeling has been conducted using protein supplements rather than whole foods, which may produce substantially different responses compared to whole food sources of protein [78]. Emerging evidence indicates that consumption of whole food protein sources effectively augments muscular development and recovery from exercise, but research is needed to further clarify the differential effects of protein from whole food and supplemental sources [79]. The modeled protein levels presented in this modeling study are generally achievable without protein supplements, however, and can be expected to meet the energy and protein needs of male bodybuilders.
Leucine intake was calculated due to its pivotal role in MPS [80]. Results indicated that scaled plant-based diets satisfied leucine requirements postulated to maximally stimulate MPS (2 g/meal) [63,64,65] by providing 11 g/day of leucine, or 2.75 g/meal, at each of four daily meals. These results align with data from the Oxford arm of the European Prospective Investigation into Cancer and Nutrition (EPIC–Oxford), in which young men who followed completely plant-based diets reported consuming a similar proportion of calories from leucine, scaling to 11 g/day if energy consumption reached the level determined for calculations in our study [81]. Similarly, Hevia-Larrain et al. (2021) found that young men who consumed 1.6 g/kg/day of protein while following completely plant-based diets and engaging in RET ingested an average of 9 g/day of leucine, with 2–3 g/meal consumed at breakfast, lunch, dinner, and evening snack [38]. When protein intake reaches this level, sufficient leucine has been consumed to maximize MPS, with additional intake producing no additional increases in RET-induced muscle mass and strength [82,83]. Furthermore, although plant-based proteins have been characterized as low in lysine and/or methionine relative to animal proteins, it has been suggested that large intake levels of plant proteins, as modeled in this study, would overcome these differences and produce a comparable adaptive response to RET [84].
This study also assessed micronutrient adequacy. Results indicated that scaled plant-based diets met recommendations for all vitamins, minerals, and essential fatty acids, with the exception of vitamin D. Vitamin D intake levels reached 536 IU/day, although 600 IU/day are recommended [10]. This finding aligns with lower intake levels observed in non-athletic and bodybuilding populations following plant-based diets [27,40], as well as bodybuilding populations following more standard diets [85]. Vitamin B12 is another established micronutrient of concern for individuals following plant-based diets [19], and projected intakes exceeded recommendations (49.4 vs. 2.4 mcg/day) [10]. These findings align with results from a recent cross-sectional study in which bodybuilders eating completely plant-based diets were reported to consume 50 mcg/day of vitamin B12 [40]. Conversely, Neufingerl et al. (2022) conducted a systematic review of nutrient intakes in non-athletic populations that reported mean vitamin B12 intakes in individuals following plant-based diets that were significantly lower (1.5 mcg/day) [27]. This may be attributable to relatively lower intakes of vitamin B12-fortified foods and beverages due to moderate energy intakes in more sedentary populations, as well as a lower prevalence of dietary supplementation in non-athletic populations [86]. Nevertheless, it can be challenging for bodybuilders to meet recommended intakes of vitamins B12 and D through fortified foods, and athletes are encouraged to ensure reliable intake of these micronutrients through the regular consumption of supplements [74,87]. Sodium intake levels (7484 mg/day) exceeded the upper limit set by the Dietary Guidelines for Americans (2300 mg/day) [10]. However, AHS-2 estimated dietary sodium using an FFQ [17], which has been shown to significantly overestimate these values [88]. Furthermore, fitness athletes sweat significantly during training, excreting approximately 1 g/hr of sodium during moderate-intensity sessions [89], which could affect sodium requirements in this population. Lastly, saturated fat was approximately 5% of total calories, which resides significantly below national recommendations to limit intake to less than 10% of total calories [10] and also meets the American Heart Association recommendations to limit saturated fat to no more than 5–6% of total calories for individuals with elevated low-density lipoprotein (LDL)-cholesterol levels [90]. This represents an improvement compared to traditional bodybuilding diets, which often contain larger quantities of saturated fat [8]. This is consequential because bodybuilders have displayed cardiovascular disease (CVD) risk factors [91,92] that may be largely attributable to diet [93]. However, the extents to which diet, chronic physical stress, and other factors contribute to the increased mortality rate associated with bodybuilding are not well understood [94]. Therefore, CVD risk in populations following completely plant-based diets compared to more typical, omnivorous diets followed by bodybuilding populations remains unknown and an area for future investigation.
The present study has several strengths. First, the sample size from which dietary intakes for a population following a completely plant-based diet was large [17]. Second, we used anthropometric data to derive energy requirements for a typical male bodybuilder [48] instead of relying on dietary assessment data for this population, which may be biased due to underreporting [95]. Third, the prediction equation used to estimate RMR has been validated in bodybuilders [57].
The study also has limitations. First, dietary intakes calculated in the AHS-2 cohort of individuals following completely plant-based diets were based on FFQ data, not more objective measures. FFQ are known to be subject to underreporting as compared to direct measures of actual intake [73]. However, because diets were scaled, it is possible this discrepancy did not affect the results. Second, we scaled dietary intake using modeling rather than direct laboratory analytical procedures, which could lead to discrepancies in projected versus actual intakes. For example, dietary fiber intakes were determined to be 99 g/day, and it has been speculated that consumption of fiber-rich foods could make it difficult for athletes requiring higher energy intakes to ingest sufficient calories due to the influence of fiber on satiety [33,35,96]. However, the selection of more calorically dense foods such as whole grains, nuts, and foods prepared with added fats as compared to fruits and vegetables alone may enable higher energy intakes. Additionally, the gastrointestinal tracts of athletes appear to be highly adaptable and permit larger calorie intakes by accelerating gastric emptying, diminishing perceptions of fullness, reducing bloating, improving tolerance to larger food volumes, and increasing absorption speed [97]. Third, modeling was performed for protein quantity but not protein quality, although this feature is more likely to influence anabolic outcomes at lower levels of protein intake than those determined in this study [63]. Popular means of calculating protein quality, such as the Digestible Indispensable Amino Acid Score (DIAAS), also display significant shortcomings that have been discussed in the context of plant-based diets [98] and limit their utility. Dietary leucine content was used to address this issue because a large body of evidence supports the leucine trigger hypothesis in explaining divergent postprandial rates of MPS in response to different protein sources [80]. The possibility exists, however, that the leucine threshold may only apply to the ingestion of isolated protein supplements rather than whole food protein sources due to differing digestion and absorption rates [80,99]. Following this, regardless of the total quantity consumed, leucine absorption and utilization may not be maximized if leucine intakes are not distributed evenly throughout the day [67,68]. However, the nutrient intakes of subjects from AHS-2 were not reported on a per-meal basis, so direct scaling of their meals may not optimally distribute their leucine contents. Additionally, a lack of dietary creatine has been proposed to limit the anabolic potential of plant-based diets [100]. We were unable to model dietary creatine intakes because levels are not reported in large cohort studies of populations following plant-based diets [27]. Although supplemental creatine has been shown to augment RET-induced increases in muscle strength [101,102] and hypertrophy [103], we have previously published that there is a lack of evidence indicating that dietary creatine also exerts these effects [100]. Finally, this study modeled levels of protein, leucine, and other key nutrients in the bodybuilding off-season, when calorie intake is high, relative to the dieting phase [8]. During contest preparation, 75% of competitive male bodybuilders have reported taking protein supplements [104], and it has been suggested that plant protein supplementation may be helpful for bodybuilders following plant-based diets since sourcing large quantities of protein from whole food sources would increase energy intake at a time when an energy deficit is required [40]. The results of this modeling study should therefore not be extrapolated to contest preparation.
This study modeled dietary intakes in young male bodybuilders following completely plant-based diets. Future research should determine protein intakes in older populations following completely plant-based diets. Protein requirements in older individuals may be greater than those in younger populations [105], although targets set in this study exceed these requirements [106]. Modeling protein intakes in female athletes would also be valuable. However, no differences have been observed between sexes regarding protein requirements beyond those related to differences in body mass for the maximization of RET-induced changes in muscular hypertrophy and strength [47]. Total energy and protein intakes in female bodybuilders are reportedly lower than in their male counterparts, likely due to their relatively lower body mass [8]. Additional research could model intakes among players of other sports following completely plant-based diets, in which levels of lean body mass are predictive of exercise performance [107,108,109,110]. Future research should also be performed using dietary data from populations outside the United States.
The findings of this modeling study have significant implications for the public health and fitness domains. They support a critical alignment between recommendations for the prevention and treatment of chronic diseases and the enhancement of muscle mass and strength in an athletic population. Dietary modeling suggests that athletes undertaking RET in pursuit of maximal gains in muscle mass and strength may meet dietary requirements by eating larger portions of commonly consumed plant-based meals.

5. Conclusions

This modeling analysis found that completely plant-based diets scaled to meet the caloric demands of maximal skeletal muscle hypertrophy and strength development in adult male bodybuilders satisfy protein, leucine, and essential micronutrient requirements necessary for maximizing RET-induced gains in muscle mass and strength. Our calculations indicate that these diets surpass the protein and leucine intakes required for optimal muscle development as recommended in existing literature, as well as most other micronutrient intake levels, with the exception of vitamin D. These findings indicate potential alignment between dietary guidelines for chronic disease prevention and sports nutrition requirements for maximal muscle hypertrophy and strength, bridging a gap that has previously separated these domains. This modeling research provides theoretical evidence that athletes adhering to completely plant-based diets can achieve their muscle-building goals while adhering to recommendations for overall health.

Author Contributions

Conceptualization, D.M.G.; methodology, D.M.G., C.B.W. and M.C.K.; investigation, D.M.G., C.B.W. and M.C.K.; writing—original draft preparation, D.M.G., C.B.W. and M.C.K.; writing—reviewing and editing, D.M.G., C.B.W. and M.C.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article.

Acknowledgments

The authors thank Gary Fraser, Rawiwan Sirirat, and Nico Rizzo for their insight and context into the dietary assessments in the AHS-2 cohort. The authors thank Blair Garneau for developing the graphical abstract. The authors also thank Cameron O’Connell for her contributions to preliminary graphics, language, and editing.

Conflicts of Interest

David M. Goldman consults for Metabite, Inc. C.B.W. and M.C.K. declare no competing interests.

References

  1. Jonason, P.K. An evolutionary psychology perspective on sex differences in exercise behaviors and motivations. J. Soc. Psychol. 2007, 147, 5–14. [Google Scholar] [CrossRef] [PubMed]
  2. Nagata, J.M.; Ganson, K.T.; Griffiths, S.; Mitchison, D.; Garber, A.K.; Vittinghoff, E.; Bibbins-Domingo, K.; Murray, S.B. Prevalence and correlates of muscle-enhancing behaviors among adolescents and young adults in the United States. Int. J. Adolesc. Med. Health 2020, 34, 119–129. [Google Scholar] [CrossRef] [PubMed]
  3. Jäger, R.; Kerksick, C.M.; Campbell, B.I.; Cribb, P.J.; Wells, S.D.; Skwiat, T.M.; Purpura, M.; Ziegenfuss, T.N.; Ferrando, A.A.; Arent, S.M.; et al. International Society of Sports Nutrition Position Stand: Protein and exercise. J. Int. Soc. Sports Nutr. 2017, 14, 20. [Google Scholar] [CrossRef] [PubMed]
  4. Musiał, K.; Wiski, M.; Lipert, A. Protein intake among healthy adults undertaking regular muscle strength training. Med. Sci. Pulse 2020, 14, 23–29. [Google Scholar] [CrossRef]
  5. Sandoval, W.M.; Heyward, V.H. Food selection patterns of bodybuilders. Int. J. Sport. Nutr. Exerc. Metab. 1991, 1, 61–68. [Google Scholar] [CrossRef] [PubMed]
  6. Panasiewicz, M.; Grochowicz, J. Ocena sposobu odżywiania i aktywności fizycznej w uprawianiu kulturystyki. Zesz. Naukowe. Tur. I Rekreac. 2016, 1, 53–68. [Google Scholar]
  7. Karpik, A.; Machniak, M.; Chwałczynska, A. Evaluation of protein content in the diet of amateur male bodybuilder. Am. J. Mens. Health 2020, 14, 1557988320970267. [Google Scholar] [CrossRef]
  8. Spendlove, J.; Mitchell, L.; Gifford, J.; Hackett, D.; Slater, G.; Cobley, S.; O’Connor, H. Dietary intake of competitive bodybuilders. Sports Med. 2015, 45, 1041–1063. [Google Scholar] [CrossRef]
  9. Bert, F.; Scaioli, G.; Tolomeo, M.; Lo Moro, G.; Gualano, M.R.; Siliquini, R. Knowledge, attitudes and eating habits red and processed meat among gym users: A cross-sectional survey. Perspect. Public. Health 2020, 140, 203–213. [Google Scholar] [CrossRef]
  10. U.S. Department of Agriculture; U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025; U.S. Department of Agriculture; U.S. Department of Health and Human Services: Washington, DC, USA, 2020.
  11. World Health Organization. Plant-Based Diets and Their Impact on Health, Sustainability and the Environment: A Review of the Evidence; Regional Office for Europe, Ed.; World Health Organization: Geneva, Switzerland, 2021. [Google Scholar]
  12. Cara, K.C.; Goldman, D.M.; Kollman, B.K.; Amato, S.S.; Tull, M.D.; Karlsen, M.C. Commonalities among dietary recommendations from 2010 to 2021 clinical practice guidelines: A meta-epidemiological study from the American College of Lifestyle Medicine. Adv. Nutr. 2023, 14, 500–515. [Google Scholar] [CrossRef]
  13. Hartwell, M.; Torgerson, T.; Essex, R.; Campbell, B.; Belardo, D.; Vassar, M. Public awareness of a plant-based diet following the release of “Game Changers” and “What the Health” documentaries. Am. J. Lifestyle Med. 2022, 16, 190–196. [Google Scholar] [CrossRef] [PubMed]
  14. Wirnitzer, K. Vegan diet in sports and exercise—Health benefits and advantages to athletes and physically active people: A narrative review. Int. J. Sports Exerc. Med. 2020, 6, 165. [Google Scholar] [CrossRef]
  15. Karlsen, M.C.; Rogers, G.; Miki, A.; Lichtenstein, A.H.; Folta, S.C.; Economos, C.D.; Jacques, P.F.; Livingston, K.A.; McKeown, N.M. Theoretical food and nutrient composition of whole-food plant-based and vegan diets compared to current dietary recommendations. Nutrients 2019, 11, 625. [Google Scholar] [CrossRef] [PubMed]
  16. Barnard, N.D.; Alwarith, J.; Rembert, E.; Brandon, L.; Nguyen, M.; Goergen, A.; Horne, T.; do Nascimento, G.F.; Lakkadi, K.; Tura, A.; et al. A Mediterranean diet and low-fat vegan diet to improve body weight and cardiometabolic risk factors: A randomized, cross-over trial. J. Am. Nutr. Assoc. 2022, 41, 127–139. [Google Scholar] [CrossRef] [PubMed]
  17. Rizzo, N.S.; Jaceldo-Siegl, K.; Sabate, J.; Fraser, G.E. Nutrient profiles of vegetarian and nonvegetarian dietary patterns. J. Acad. Nutr. Diet. 2013, 113, 1610–1619. [Google Scholar] [CrossRef] [PubMed]
  18. Wright, N.; Wilson, L.; Smith, M.; Duncan, B.; McHugh, P. The BROAD study: A randomised controlled trial using a whole food plant-based diet in the community for obesity, ischaemic heart disease or diabetes. Nutr. Diabetes 2017, 7, e256. [Google Scholar] [CrossRef]
  19. Melina, V.; Craig, W.; Levin, S. Position of the Academy of Nutrition and Dietetics: Vegetarian diets. J. Acad. Nutr. Diet. 2016, 116, 1970–1980. [Google Scholar] [CrossRef] [PubMed]
  20. Fogelholm, M. Dairy products, meat and sports performance. Sports Med. 2003, 33, 615–631. [Google Scholar] [CrossRef]
  21. Venderley, A.M.; Campbell, W.W. Vegetarian diets: Nutritional considerations for athletes. Sports Med. 2006, 36, 293–305. [Google Scholar] [CrossRef]
  22. Lynch, H.; Johnston, C.; Wharton, C. Plant-based diets: Considerations for environmental impact, protein quality, and exercise performance. Nutrients 2018, 10, 1841. [Google Scholar] [CrossRef]
  23. Messina, M.; Lynch, H.; Dickinson, J.M.; Reed, K.E. No difference between the effects of supplementing with soy protein versus animal protein on gains in muscle mass and strength in response to resistance exercise. Int. J. Sport. Nutr. Exerc. Metab. 2018, 28, 674–685. [Google Scholar] [CrossRef] [PubMed]
  24. Burd, N.A.; McKenna, C.F.; Salvador, A.F.; Paulussen, K.J.M.; Moore, D.R. Dietary protein quantity, quality, and exercise are key to healthy living: A muscle-centric perspective across the lifespan. Front. Nutr. 2019, 6, 83. [Google Scholar] [CrossRef] [PubMed]
  25. Ciuris, C.; Lynch, H.M.; Wharton, C.; Johnston, C.S. A comparison of dietary protein digestibility, based on DIAAS scoring, in vegetarian and non-vegetarian athletes. Nutrients 2019, 11, 3016. [Google Scholar] [CrossRef] [PubMed]
  26. Zhou, J.; Li, J.; Campbell, W.W. Vegetarian athletes. In Nutrition and Enhanced Sports Performance; Elsevier: Amsterdam, The Netherlands, 2019; pp. 99–108. [Google Scholar]
  27. Neufingerl, N.; Eilander, A. Nutrient intake and status in adults consuming plant-based diets compared to meat-eaters: A systematic review. Nutrients 2021, 14, 29. [Google Scholar] [CrossRef] [PubMed]
  28. Mariotti, F. Vegetarian and Plant-Based Diets in Health and Disease Prevention; Academic Press: Cambridge, MA, USA, 2017. [Google Scholar]
  29. Gorissen, S.H.M.; Witard, O.C. Characterising the muscle anabolic potential of dairy, meat and plant-based protein sources in older adults. Proc. Nutr. Soc. 2018, 77, 20–31. [Google Scholar] [CrossRef] [PubMed]
  30. Phillips, S.M. The impact of protein quality on the promotion of resistance exercise-induced changes in muscle mass. Nutr. Metab. 2016, 13, 64. [Google Scholar] [CrossRef] [PubMed]
  31. Li, C.Y.; Fang, A.P.; Ma, W.J.; Wu, S.L.; Li, C.L.; Chen, Y.M.; Zhu, H.L. Amount rather than animal vs plant protein intake is associated with skeletal muscle mass in community-dwelling middle-aged and older Chinese adults: Results from the Guangzhou Nutrition and Health Study. J. Acad. Nutr. Diet. 2019, 119, 1501–1510. [Google Scholar] [CrossRef] [PubMed]
  32. Atherton, P.J.; Smith, K. Muscle protein synthesis in response to nutrition and exercise. J. Physiol. 2012, 590, 1049–1057. [Google Scholar] [CrossRef]
  33. Maughan, R.J. Nutrition in Sport; John Wiley & Sons: Hoboken, NJ, USA, 2008; Volume 7. [Google Scholar]
  34. Wolinsky, I.; Driskell, J.A. Nutritional Applications in Exercise and Sport; CRC Press: Boca Raton, FL, USA, 2000. [Google Scholar]
  35. Rogerson, D. Vegan diets: Practical advice for athletes and exercisers. J. Int. Soc. Sports Nutr. 2017, 14, 36. [Google Scholar] [CrossRef]
  36. Bagchi, D.; Nair, S.; Sen, C.K. Nutrition and Enhanced Sports Performance: Muscle Building, Endurance, and Strength; Academic Press: Cambridge, MA, USA, 2018. [Google Scholar]
  37. Nebl, J.; Schuchardt, J.P.; Wasserfurth, P.; Haufe, S.; Eigendorf, J.; Tegtbur, U.; Hahn, A. Characterization, dietary habits and nutritional intake of omnivorous, lacto-ovo vegetarian and vegan runners—A pilot study. BMC Nutr. 2019, 5, 51. [Google Scholar] [CrossRef]
  38. Hevia-Larraín, V.; Gualano, B.; Longobardi, I.; Gil, S.; Fernandes, A.L.; Costa, L.A.R.; Pereira, R.M.R.; Artioli, G.G.; Phillips, S.M.; Roschel, H. High-protein plant-based diet versus a protein-matched omnivorous diet to support resistance training adaptations: A comparison between habitual vegans and omnivores. Sports Med. 2021, 51, 1317–1330. [Google Scholar] [CrossRef] [PubMed]
  39. Wirnitzer, K.; Wagner, K.H.; Motevalli, M.; Tanous, D.; Wirnitzer, G.; Leitzmann, C.; Rosemann, T.; Knechtle, B. Dietary intake of vegan and non-vegan endurance runners-Results from the NURMI Study (Step 2). Nutrients 2022, 14, 3151. [Google Scholar] [CrossRef]
  40. Amatori, S.; Callarelli, C.; Gobbi, E.; Bertuccioli, A.; Donati Zeppa, S.; Sisti, D.; Rocchi, M.B.L.; Perroni, F. Going vegan for the gain: A cross-sectional study of vegan diets in bodybuilders during different preparation phases. Int. J. Environ. Res. Public. Health 2023, 20, 5187. [Google Scholar] [CrossRef] [PubMed]
  41. Craddock, J.C.; Probst, Y.C.; Neale, E.P.; Geraghty, N.; Peoples, G.E. A comparison of diet quality and cardiovascular and inflammatory responses between aerobically trained male adults following either a long-term vegan or omnivorous dietary pattern. Nutr. Bull. 2023, 48, 227–242. [Google Scholar] [CrossRef]
  42. Monteyne, A.J.; Coelho, M.O.C.; Murton, A.J.; Abdelrahman, D.R.; Blackwell, J.R.; Koscien, C.P.; Knapp, K.M.; Fulford, J.; Finnigan, T.J.A.; Dirks, M.L.; et al. Vegan and omnivorous high protein diets support comparable daily myofibrillar protein synthesis rates and skeletal muscle hypertrophy in young adults. J. Nutr. 2023, 153, 1680–1695. [Google Scholar] [CrossRef] [PubMed]
  43. Nunes, E.A.; Colenso-Semple, L.; McKellar, S.R.; Yau, T.; Ali, M.U.; Fitzpatrick-Lewis, D.; Sherifali, D.; Gaudichon, C.; Tomé, D.; Atherton, P.J.; et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. J. Cachexia Sarcopenia Muscle 2022, 13, 795–810. [Google Scholar] [CrossRef] [PubMed]
  44. Slater, G.; Phillips, S.M. Nutrition guidelines for strength sports: Sprinting, weightlifting, throwing events, and bodybuilding. J. Sports Sci. 2011, 29 (Suppl. S1), S67–S77. [Google Scholar] [CrossRef] [PubMed]
  45. Alves, R.C.; Prestes, J.; Enes, A.; de Moraes, W.M.A.; Trindade, T.B.; de Salles, B.F.; Aragon, A.A.; Souza-Junior, T.P. Training programs designed for muscle hypertrophy in bodybuilders: A narrative review. Sports 2020, 8, 149. [Google Scholar] [CrossRef] [PubMed]
  46. Schoenfeld, B.; Fisher, J.; Grgic, J.; Haun, C.; Helms, E.; Phillips, S.; Steele, J.; Vigotsky, A. Resistance training recommendations to maximize muscle hypertrophy in an athletic population: Position stand of the IUSCA. Int. J. Strength Cond. 2021, 1, 1–30. [Google Scholar] [CrossRef]
  47. Morton, R.W.; Murphy, K.T.; McKellar, S.R.; Schoenfeld, B.J.; Henselmans, M.; Helms, E.; Aragon, A.A.; Devries, M.C.; Banfield, L.; Krieger, J.W.; et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br. J. Sports Med. 2018, 52, 376–384. [Google Scholar] [CrossRef]
  48. Bauer, P.; Majisik, A.; Mitter, B.; Csapo, R.; Tschan, H.; Hume, P.; Martínez-Rodríguez, A.; Makivic, B. Body composition of competitive bodybuilders: A systematic review of published data and recommendations for future work. J. Strength Cond. Res. 2023, 37, 726–732. [Google Scholar] [CrossRef] [PubMed]
  49. Clem, J.; Barthel, B. A look at plant-based diets. Mo. Med. 2021, 118, 233–238. [Google Scholar] [PubMed]
  50. Appleton, T.; Masters, M. 10 Best Vegan Protein Powders for Muscle Building in 2024, Tested by Experts. 14 February 2024. Available online: https://www.menshealth.com/nutrition/a19541471/best-vegan-protein-powders/ (accessed on 16 March 2024).
  51. Baby, D.P. Are Vegan Protein Powders Good for You? 2022. Available online: https://www.medicinenet.com/are_vegan_protein_powders_good_for_you/article.htm (accessed on 16 March 2024).
  52. Hackett, D.A. Training, supplementation, and pharmacological practices of competitive male bodybuilders across training phases. J. Strength Cond. Res. 2022, 36, 963–970. [Google Scholar] [CrossRef]
  53. Li, J.; Davies, T.B.; Hackett, D.A. Self-reported training and supplementation practices between performance-enhancing drug-user bodybuilders compared with natural bodybuilders. J. Strength Cond. Res. 2023, 37, 1079–1088. [Google Scholar] [CrossRef] [PubMed]
  54. Slater, G.J.; Dieter, B.P.; Marsh, D.J.; Helms, E.R.; Shaw, G.; Iraki, J. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Front. Nutr. 2019, 6, 131. [Google Scholar] [CrossRef] [PubMed]
  55. Aragon, A.A.; Schoenfeld, B.J. Magnitude and composition of the energy surplus for maximizing muscle hypertrophy: Implications for bodybuilding and physique athletes. Strength Cond. J. 2020, 42, 79–86. [Google Scholar] [CrossRef]
  56. O’Neill, J.E.R.; Corish, C.A.; Horner, K. Accuracy of resting metabolic rate prediction equations in athletes: A systematic review with meta-analysis. Sports Med. 2023, 53, 2373–2398. [Google Scholar] [CrossRef]
  57. Tinsley, G.M.; Graybeal, A.J.; Moore, M.L. Resting metabolic rate in muscular physique athletes: Validity of existing methods and development of new prediction equations. Appl. Physiol. Nutr. Metab. 2019, 44, 397–406. [Google Scholar] [CrossRef] [PubMed]
  58. Karpinski, C.; Rosenbloom, C.A. Sports Nutrition: A Handbook for Professionals; Academy of Nutrition and Dietetics: Chicago, IL, USA, 2017. [Google Scholar]
  59. Schoenfeld, B.J.; Ogborn, D.; Krieger, J.W. Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. J. Sports Sci. 2017, 35, 1073–1082. [Google Scholar] [CrossRef]
  60. Maughan, R.J.; Burke, L.M.; Dvorak, J.; Larson-Meyer, D.E.; Peeling, P.; Phillips, S.M.; Rawson, E.S.; Walsh, N.P.; Garthe, I.; Geyer, H.; et al. IOC consensus statement: Dietary supplements and the high-performance athlete. Int. J. Sport. Nutr. Exerc. Metab. 2018, 28, 104–125. [Google Scholar] [CrossRef]
  61. Glynn, E.L.; Fry, C.S.; Drummond, M.J.; Timmerman, K.L.; Dhanani, S.; Volpi, E.; Rasmussen, B.B. Excess leucine intake enhances muscle anabolic signaling but not net protein anabolism in young men and women. J. Nutr. 2010, 140, 1970–1976. [Google Scholar] [CrossRef]
  62. Pinckaers, P.J.M.; Kouw, I.W.K.; Hendriks, F.K.; van Kranenburg, J.M.X.; de Groot, L.; Verdijk, L.B.; Snijders, T.; van Loon, L.J.C. No differences in muscle protein synthesis rates following ingestion of wheat protein, milk protein, and their protein blend in healthy, young males. Br. J. Nutr. 2021, 126, 1832–1842. [Google Scholar] [CrossRef] [PubMed]
  63. Reidy, P.T.; Rasmussen, B.B. Role of ingested amino acids and protein in the promotion of resistance exercise-induced muscle protein anabolism. J. Nutr. 2016, 146, 155–183. [Google Scholar] [CrossRef]
  64. Lynch, H.M.; Buman, M.P.; Dickinson, J.M.; Ransdell, L.B.; Johnston, C.S.; Wharton, C.M. No significant differences in muscle growth and strength development when consuming soy and whey protein supplements matched for leucine following a 12 week resistance training program in men and women: A randomized trial. Int. J. Environ. Res. Public. Health 2020, 17, 3871. [Google Scholar] [CrossRef]
  65. Olaniyan, E.T.; O’Halloran, F.; McCarthy, A.L. Dietary protein considerations for muscle protein synthesis and muscle mass preservation in older adults. Nutr. Res. Rev. 2021, 34, 147–157. [Google Scholar] [CrossRef]
  66. Iraki, J.; Fitschen, P.; Espinar, S.; Helms, E. Nutrition recommendations for bodybuilders in the off-season: A narrative review. Sports 2019, 7, 154. [Google Scholar] [CrossRef] [PubMed]
  67. Schoenfeld, B.J.; Aragon, A.A. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J. Int. Soc. Sports Nutr. 2018, 15, 10. [Google Scholar] [CrossRef] [PubMed]
  68. Kerksick, C.M.; Arent, S.; Schoenfeld, B.J.; Stout, J.R.; Campbell, B.; Wilborn, C.D.; Taylor, L.; Kalman, D.; Smith-Ryan, A.E.; Kreider, R.B.; et al. International Society of Sports Nutrition Position Stand: Nutrient timing. J. Int. Soc. Sports Nutr. 2017, 14, 33. [Google Scholar] [CrossRef]
  69. Berrazaga, I.; Micard, V.; Gueugneau, M.; Walrand, S. The role of the anabolic properties of plant- versus animal-based protein sources in supporting muscle mass maintenance: A critical review. Nutrients 2019, 11, 1825. [Google Scholar] [CrossRef]
  70. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements; The National Academies Press: Washington, DC, USA, 2011. [Google Scholar]
  71. United States Department of Health and Human Services. Dietary Reference Intakes. 2023. Available online: https://health.gov/our-work/nutrition-physical-activity/dietary-guidelines/dietary-reference-intakes (accessed on 21 January 2024).
  72. Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline; National Academy Press: Washington, DC, USA, 1998. [Google Scholar]
  73. McKenzie, B.L.; Coyle, D.H.; Santos, J.A.; Burrows, T.; Rosewarne, E.; Peters, S.A.E.; Carcel, C.; Jaacks, L.M.; Norton, R.; Collins, C.E.; et al. Investigating sex differences in the accuracy of dietary assessment methods to measure energy intake in adults: A systematic review and meta-analysis. Am. J. Clin. Nutr. 2021, 113, 1241–1255. [Google Scholar] [CrossRef]
  74. Baroni, L.; Pelosi, E.; Giampieri, F.; Battino, M. The VegPlate for Sports: A plant-based food guide for athletes. Nutrients 2023, 15, 1746. [Google Scholar] [CrossRef] [PubMed]
  75. Antonio, J.; Ellerbroek, A. Case reports on well-trained bodybuilders: Two years on a high protein diet. J. Exerc. Physiol. Online 2018, 21, 14–24. [Google Scholar]
  76. Hernández-Martínez, C.; Fernández-Rodríguez, L.; Soriano, M.A.; Martínez-Sanz, J.M. Case study: Body composition changes resulting from a nutritional intervention on a professional vegan powerlifter. Appl. Sci. 2020, 10, 8675. [Google Scholar] [CrossRef]
  77. Karlsen, M.C. (American College of Lifestyle Medicine, Chesterfield, MO, USA; University of New England, Biddeford, ME, USA); Goldman, D.M. (Metabite, Inc. New York, NY, USA). Personal Communication, 2023.
  78. Trommelen, J.; Betz, M.W.; van Loon, L.J.C. The muscle protein synthetic response to meal ingestion following resistance-type exercise. Sports Med. 2019, 49, 185–197. [Google Scholar] [CrossRef] [PubMed]
  79. Burd, N.A.; Beals, J.W.; Martinez, I.G.; Salvador, A.F.; Skinner, S.K. Food-first approach to enhance the regulation of post-exercise skeletal muscle protein synthesis and remodeling. Sports Med. 2019, 49, 59–68. [Google Scholar] [CrossRef]
  80. Zaromskyte, G.; Prokopidis, K.; Ioannidis, T.; Tipton, K.D.; Witard, O.C. Evaluating the leucine trigger hypothesis to explain the post-prandial regulation of muscle protein synthesis in young and older adults: A systematic review. Front. Nutr. 2021, 8, 685165. [Google Scholar] [CrossRef]
  81. Schmidt, J.A.; Rinaldi, S.; Scalbert, A.; Ferrari, P.; Achaintre, D.; Gunter, M.J.; Appleby, P.N.; Key, T.J.; Travis, R.C. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: A cross-sectional analysis in the EPIC-Oxford cohort. Eur. J. Clin. Nutr. 2016, 70, 306–312. [Google Scholar] [CrossRef] [PubMed]
  82. Aguiar, A.F.; Grala, A.P.; da Silva, R.A.; Soares-Caldeira, L.F.; Pacagnelli, F.L.; Ribeiro, A.S.; da Silva, D.K.; de Andrade, W.B.; Balvedi, M.C.W. Free leucine supplementation during an 8-week resistance training program does not increase muscle mass and strength in untrained young adult subjects. Amino Acids 2017, 49, 1255–1262. [Google Scholar] [CrossRef] [PubMed]
  83. De Andrade, I.; Gualano, B.; Hevia-Larraín, V.; Neves-Junior, J.; Cajueiro, M.; Jardim, F.; Gomes, R.L.; Artioli, G.G.; Phillips, S.M.; Campos-Ferraz, P.; et al. Leucine supplementation has no further effect on training-induced muscle adaptations. Med. Sci. Sports Exerc. 2020, 52, 1809–1814. [Google Scholar] [CrossRef]
  84. Pinckaers, P.J.M.; Trommelen, J.; Snijders, T.; van Loon, L.J.C. The anabolic response to plant-based protein ingestion. Sports Med. 2021, 51 (Suppl. S1), 59–74. [Google Scholar] [CrossRef]
  85. Ismaeel, A.; Weems, S.; Willoughby, D.S. A comparison of the nutrient intakes of macronutrient-based dieting and strict dieting bodybuilders. Int. J. Sport. Nutr. Exerc. Metab. 2018, 28, 502–508. [Google Scholar] [CrossRef] [PubMed]
  86. Knapik, J.J.; Steelman, R.A.; Hoedebecke, S.S.; Austin, K.G.; Farina, E.K.; Lieberman, H.R. Prevalence of dietary supplement use by athletes: Systematic review and meta-analysis. Sports Med. 2016, 46, 103–123. [Google Scholar] [CrossRef]
  87. West, S.; Monteyne, A.J.; van der Heijden, I.; Stephens, F.B.; Wall, B.T. Nutritional considerations for the vegan athlete. Adv. Nutr. 2023, 14, 774–795. [Google Scholar] [CrossRef] [PubMed]
  88. McLean, R.M.; Farmer, V.L.; Nettleton, A.; Cameron, C.M.; Cook, N.R.; Campbell, N.R.C. Assessment of dietary sodium intake using a food frequency questionnaire and 24-hour urinary sodium excretion: A systematic literature review. J. Clin. Hyperte. 2017, 19, 1214–1230. [Google Scholar] [CrossRef]
  89. Barnes, K.A.; Anderson, M.L.; Stofan, J.R.; Dalrymple, K.J.; Reimel, A.J.; Roberts, T.J.; Randell, R.K.; Ungaro, C.T.; Baker, L.B. Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: An update and analysis by sport. J. Sports Sci. 2019, 37, 2356–2366. [Google Scholar] [CrossRef] [PubMed]
  90. Eckel, R.H.; Jakicic, J.M.; Ard, J.D.; de Jesus, J.M.; Houston Miller, N.; Hubbard, V.S.; Lee, I.M.; Lichtenstein, A.H.; Loria, C.M.; Millen, B.E.; et al. 2013 AHA/ACC guideline on lifestyle management to reduce cardiovascular risk: A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines. J. Am. Coll. Cardiol. 2014, 63, 2960–2984. [Google Scholar] [CrossRef]
  91. Brito, A.P.; Rêgo, A.S.; Sousa, L.M.; Ewerton, F.A.; Bragança, M.L.; Silva, F.M.; Barbosa, J.M. Cardiovascular risk in bodybuilders in gyms in São Luís, state of Maranhão. Rev. Atenção Saúde 2020, 19, 107–121. [Google Scholar] [CrossRef]
  92. Coraucci-Neto, B.; Bertani, R.F.; Campos, G.O.; Bonardi, J.M.; Lima, N.K. Health aspects of active bodybuilders: Monitoring by multidisciplinary team. Rev. Bras. Ciências Esporte 2021, 43, e007321. [Google Scholar] [CrossRef]
  93. Kleiner, S.M.; Calabrese, L.H.; Fiedler, K.M.; Naito, H.K.; Skibinski, C.I. Dietary influences on cardiovascular disease risk in anabolic steroid-using and nonusing bodybuilders. J. Am. Coll. Nutr. 1989, 8, 109–119. [Google Scholar] [CrossRef]
  94. Smoliga, J.M.; Wilber, Z.T.; Robinson, B.T. Premature death in bodybuilders: What do we know? Sports Med. 2023, 53, 933–948. [Google Scholar] [CrossRef]
  95. Andrade, C. Sample size and its importance in research. Indian. J. Psychol. Med. 2020, 42, 102–103. [Google Scholar] [CrossRef] [PubMed]
  96. Wolinsky, I. Nutrition in Exercise and Sport; CRC Press: Boca Raton, FL, USA, 1997; Volume 13. [Google Scholar]
  97. Jeukendrup, A.E. Training the gut for athletes. Sports Med. 2017, 47 (Suppl. S1), 101–110. [Google Scholar] [CrossRef] [PubMed]
  98. Craddock, J.C.; Genoni, A.; Strutt, E.F.; Goldman, D.M. Limitations with the Digestible Indispensable Amino Acid Score (DIAAS) with special attention to plant-based diets: A review. Curr. Nutr. Rep. 2021, 10, 93–98. [Google Scholar] [CrossRef] [PubMed]
  99. Vliet, S.V.; Beals, J.W.; Martinez, I.G.; Skinner, S.K.; Burd, N.A. Achieving optimal post-exercise muscle protein remodeling in physically active adults through whole food consumption. Nutrients 2018, 10, 224. [Google Scholar] [CrossRef]
  100. Goldman, D.M.; Stiegmann, R.A.; Craddock, J.C. Supplemental creatine, not dietary creatine, appears to improve exercise performance in individuals following omnivorous or meat-free diets: A narrative review. Int. J. Dis. Rev. Prev. 2022, 4, 15. [Google Scholar] [CrossRef]
  101. Lanhers, C.; Pereira, B.; Naughton, G.; Trousselard, M.; Lesage, F.X.; Dutheil, F. Creatine supplementation and lower limb strength performance: A systematic review and meta-analyses. Sports Med. 2015, 45, 1285–1294. [Google Scholar] [CrossRef] [PubMed]
  102. Lanhers, C.; Pereira, B.; Naughton, G.; Trousselard, M.; Lesage, F.X.; Dutheil, F. Creatine supplementation and upper limb strength performance: A systematic review and meta-analysis. Sports Med. 2017, 47, 163–173. [Google Scholar] [CrossRef]
  103. Delpino, F.M.; Figueiredo, L.M.; Forbes, S.C.; Candow, D.G.; Santos, H.O. Influence of age, sex, and type of exercise on the efficacy of creatine supplementation on lean body mass: A systematic review and meta-analysis of randomized clinical trials. Nutrition 2022, 103–104, 111791. [Google Scholar] [CrossRef] [PubMed]
  104. Chappell, A.J.; Simper, T.; Barker, M.E. Nutritional strategies of high level natural bodybuilders during competition preparation. J. Int. Soc. Sports Nutr. 2018, 15, 4. [Google Scholar] [CrossRef]
  105. Witard, O.C.; Wardle, S.L.; Macnaughton, L.S.; Hodgson, A.B.; Tipton, K.D. Protein considerations for optimising skeletal muscle mass in healthy young and older adults. Nutrients 2016, 8, 181. [Google Scholar] [CrossRef]
  106. Finger, D.; Goltz, F.R.; Umpierre, D.; Meyer, E.; Rosa, L.H.; Schneider, C.D. Effects of protein supplementation in older adults undergoing resistance training: A systematic review and meta-analysis. Sports Med. 2015, 45, 245–255. [Google Scholar] [CrossRef] [PubMed]
  107. Shields, C.L., Jr.; Whitney, F.E.; Zomar, V.D. Exercise performance of professional football players. Am. J. Sports Med. 1984, 12, 455–459. [Google Scholar] [CrossRef] [PubMed]
  108. Secora, C.A.; Latin, R.W.; Berg, K.E.; Noble, J.M. Comparison of physical and performance characteristics of NCAA Division I football players: 1987 and 2000. J. Strength Cond. Res. 2004, 18, 286–291. [Google Scholar] [CrossRef] [PubMed]
  109. Pasin, F.; Caroli, B.; Spigoni, V.; Dei Cas, A.; Volpi, R.; Galli, C.; Passeri, G. Performance and antrhropometric characteristics of elite rugby players. Acta Biomed. 2017, 88, 172–177. [Google Scholar] [CrossRef]
  110. Vaz, L.; Kraak, W.; Batista, M.; Honório, S.; Miguel Fernandes, H. Using anthropometric data and physical fitness scores to predict selection in a national U19 rugby union team. Int. J. Environ. Res. Public. Health 2021, 18, 1499. [Google Scholar] [CrossRef]
Nutrients 16 01122 g001
Figure 1. Protein and leucine levels scaled to meet the energy requirements of adult male bodybuilders following completely plant-based diets during the bulking phase, in relation to thresholds proposed to maximize gains in muscle mass and strength in response to resistance exercise training. g: grams; kg: kilograms. Footnotes: a Total protein requirements to maximize RET-induced increases in muscle mass and strength were determined as the product of 1.6 g/kg/day and mean athlete body mass in the population used for modeling [47,60]. b 1.6 g/kg/day was used as the target relative protein intake, based on a consensus statement from the International Olympic Committee [60], which recommends daily protein intakes for high-performance athletes pursuing maximal muscular hypertrophy and strength of 1.6 g/kg/day [47]. c Modeled total leucine target was set at 8 g/day because a solution to meet protein and amino acid requirements has been made to consume four protein-rich meals per day [67], one every three to four hours, to optimize MPS [68]. d Modeled leucine target was set at 2 g/meal because this quantity maximally stimulates MPS in young adults [61,62] and levels that reach or exceed this target exert similar anabolic effects regardless of whether they are sourced from animal- or plant-based proteins [63,64,65].
Figure 1. Protein and leucine levels scaled to meet the energy requirements of adult male bodybuilders following completely plant-based diets during the bulking phase, in relation to thresholds proposed to maximize gains in muscle mass and strength in response to resistance exercise training. g: grams; kg: kilograms. Footnotes: a Total protein requirements to maximize RET-induced increases in muscle mass and strength were determined as the product of 1.6 g/kg/day and mean athlete body mass in the population used for modeling [47,60]. b 1.6 g/kg/day was used as the target relative protein intake, based on a consensus statement from the International Olympic Committee [60], which recommends daily protein intakes for high-performance athletes pursuing maximal muscular hypertrophy and strength of 1.6 g/kg/day [47]. c Modeled total leucine target was set at 8 g/day because a solution to meet protein and amino acid requirements has been made to consume four protein-rich meals per day [67], one every three to four hours, to optimize MPS [68]. d Modeled leucine target was set at 2 g/meal because this quantity maximally stimulates MPS in young adults [61,62] and levels that reach or exceed this target exert similar anabolic effects regardless of whether they are sourced from animal- or plant-based proteins [63,64,65].
Nutrients 16 01122 g001
Table 1. Physical parameters of male bodybuilders.
Table 1. Physical parameters of male bodybuilders.
ParameterRangeMedian Value
Age (y)22–3528.5
Body mass (kg)75–9484.5
y: years; kg: kilograms.
Table 2. Calculated energy requirement calculations for male bodybuilders.
Table 2. Calculated energy requirement calculations for male bodybuilders.
RMR: 2106 kcal/day
ES: 553 kcal/day
EER: 4239 kcal/day
ES: energy surplus; kcal: kilocalories; kg: kilograms; RMR: resting metabolic rate.
Table 3. Calculated protein requirements and levels for male bodybuilders adhering to completely plant-based diets during the bulking phase.
Table 3. Calculated protein requirements and levels for male bodybuilders adhering to completely plant-based diets during the bulking phase.
Total protein requirements: 135 g/day
Total protein levels: 151 g/day
Relative protein levels: 1.8 g/kg/day
g: grams; kg: kilograms.
Table 4. Scaled micronutrient and other key nutrient levels and requirements for male bodybuilders following completely plant-based diets.
Table 4. Scaled micronutrient and other key nutrient levels and requirements for male bodybuilders following completely plant-based diets.
AHS-2 Strict VegetariansMale
Bodybuilders ‡		Nutrient
Target		RecommendationTarget Met?
Calories (kcal)20004239--N/A
Saturated Fat (% kcal)55<10DGA✓
ω3 PUFA (g)24.21.6AI✓
Linoleic Acid (g)19.54117AI✓
Fiber (g)479959 †AI✓
Vitamin A (mcg RAE *)11082348900RDA✓
Vitamin B6 (mg)14.430.51.3RDA✓
Folate (mcg)8881882400RDA✓
Vitamin B12 (mcg)23.349.42.4RDA✓
Vitamin C (mg)531112590RDA✓
Vitamin D (IU)252536600RDA✗
Vitamin E (mg)10121415RDA✓
Calcium (mg)115624501000RDA✓
Iron (mg)32678RDA✓
Magnesium (mg)6521382400RDA✓
Phosphorus (mg)13712906700RDA✓
Potassium (mg)423489733400AI✓
Sodium (mg)353174842300CDRR✗
Zinc (mg)163511RDA✓
AI: Adequate Intake; CDRR: Chronic Disease Risk Reduction Level; DGA: Dietary Guidelines for Americans; DRI: Daily Recommended Intake; N/A: not applicable; ω3 PUFA: omega-3 polyunsaturated fatty acids; RDA: Recommended Dietary Allowance; RAE: Retinol Activity Equivalents. Data for AHS-2 strict vegetarians [17]. * Recommendations for Vitamin A provided in Retinol Activity Equivalents (RAE) to account for different bioactivities of provitamin A carotenoids [72]. † Based on recommendations to consume 14 g/1000 kcal [70]. ‡ Calorie intake represents the estimated energy requirements needed to maximize muscle hypertrophy for adult male bodybuilders. Mean micronutrient intakes per 2000 kcal/day reported in the AHS-2 dataset [17] were scaled proportionately to 4239 kcal/day.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Goldman, D.M.; Warbeck, C.B.; Karlsen, M.C. Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study. Nutrients 2024, 16, 1122. https://doi.org/10.3390/nu16081122

AMA Style

Goldman DM, Warbeck CB, Karlsen MC. Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study. Nutrients. 2024; 16(8):1122. https://doi.org/10.3390/nu16081122

Chicago/Turabian Style

Goldman, David M., Cassandra B. Warbeck, and Micaela C. Karlsen. 2024. "Completely Plant-Based Diets That Meet Energy Requirements for Resistance Training Can Supply Enough Protein and Leucine to Maximize Hypertrophy and Strength in Male Bodybuilders: A Modeling Study" Nutrients 16, no. 8: 1122. https://doi.org/10.3390/nu16081122

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop