1. Introduction
Over the past two decades, China has been undergoing remarkable nutrition transition and concurrent shifts in disease patterns with rapid economic growth [
1,
2,
3,
4]. The epidemic of nutrition related non-communicable diseases (NR-NCDs) including obesity, type 2 diabetes mellitus, cardiovascular diseases (CVDs), and certain cancers are continuing to challenge the health sectors in Asia [
5,
6,
7,
8,
9]. As the biggest developing country, about 49% of China’s population is female. Women being vulnerable section, the impact of nutrition intake on their health is much higher [
10]. It has been reported in developing countries, women have higher rates of overweight and obesity and this relationship persists over time [
11]. According to the Chinese chronic disease surveillance, the prevalence of overweight and obesity of adult females were rising rapidly in recent years and up to 29.9% and 11.9%, respectively. Therefore, it is meaningful to assess the dietary intake of Chinese females and compare it to the participants of the same age group in the Dietary Reference Intakes (DRI). Furthermore, with repeated measurements over time it is possible to detect temporal changes in dietary intake.
National diet and nutrition surveys provide valuable information on a possible partial explanation for the people’s health status and disease risk [
12]. In developing countries, this has been emphasized subject to many studies on children and the elderly, but ignored adult females [
13,
14,
15]. Recently, increasing number of women are participating in the labor market. But still, women are, at large, responsible for household food preparation. In developing countries, with the population structure and economic transformation, media, fashion and other cultural influences on the nutrition transition become more prominent. Current consumption patterns of Chinese people seem to be converging towards a western diet [
16]. Women may be more likely to accept these cultural influences, and the effect of culture is attached great importance to slim appearance. The desire to lean often leads to dieting or refusal to hunger, which can lead to emotional eating [
17,
18]. The increase in external and emotional eating is often associated with overeating and increased obesity [
19,
20]. Several studies on dietary patterns have shown the associations of obesity with specific dietary patterns among women, although the results are not consistent [
21,
22,
23]. Nutrients intake was associated with reproductive hormone concentrations and differences between macronutrient intake and menstrual cycle phase [
24,
25,
26], thus, it is important to consider women’s age-specific data when examining relationships between eating behaviors and health status.
Each of the macronutrients, carbohydrate, protein and fat, has a unique set of properties that influence health, but all are a source of energy. The optimal balance of their contribution to the diet has been a long-standing matter of debate [
27]. Epidemiological studies suggest that carbohydrate intake and protein intake are inversely associated with body-mass index (BMI), while fat intake is positively associated with BMI [
28,
29,
30]. However, studies examining trends in macronutrient intake over time have shown inconsistent results. Using longitudinal data from the China Health and Nutrition Survey (1991–2015, CHNS), the objective of this study was to analyze the trends in daily energy and macronutrient intakes among Chinese females and to investigate whether the macronutrient intake levels met the dietary reference intakes (DRI) [
31]. The paper attempts to shed some light on the determinant food habit and nutritional status of the adult women in China concentrating the socio-economic status and BMI by the interpretation of a descriptive study related with nutritional status of the women.
4. Discussion
This is the first attempt to report daily energy and macronutrient intakes in representative female samples from nine major provinces across the country using 2015 updated CHNS data. The present study is an effort to determine the nutritional status of the Chinese adult females concentrating the social-economic status and BMI categories by the interpretation of a longitudinal descriptive study related with nutritional status. During the past decades, a significant reduction in daily energy, protein and carbohydrate intakes was seen in all categories among all adult females in China. Conversely, fat intake of the females tends to increase from 1991 to 2015. Findings from the present research indicate that Chinese adult females have been undergoing a rapid nutrition transition towards a low-carbohydrate and high-fat diet. The observed trend is consistent with that in Swedish women between 2007 and 2012 [
39]. It is noteworthy in our study that the largest transition in dietary patterns took place in females from primary/illiterate education level.
Our study shows that dietary energy intake in Chinese adult females declined significantly over the past two decades. It is consistence with a previous study in Indian rural women, whose energy intake decrease steadily from 2014.0 kcal in 1997 to 1780.0 kcal in 2011 [
40]. Given the rapid increase in the prevalence of overweight and obesity in Chinese women, a potential explanation for this decline in total energy intake is a decrease in total energy expenditure [
41]. Large studies conducted in China, in particular using data of the CHNS, reported average physical activity by the occupational, domestic, active leisure and travel domains decreased with modernization among adult women from 1991 to 2011 [
42]. Up to the highest education level, energy intake was gradually declined. This is probably associated with increased awareness of health issues associated with excess energy. These findings agree with a previous study in developed countries, which showed calorie consumption is inversely associated with education levels [
43]. The low energy of high-earning women and those live in urban areas may be due to more job opportunities, service of health professionals and availability of recreational facilities that have changed those behaviors that are not conducive to controlling obesity. Meanwhile, cost is a strong influence on food purchases and given that persons of low social-economics status (SES) often have more limited budgets, healthier foods such as fruit and vegetables may be overlooked in favor of less healthy, more energy-dense options [
44]. In addition, this study found that the overweight/obese subjects consumed more energy than those normal weight women, confirms that obese people need more energy to maintain their weight. This positive correlation between energy intake and body weight status is further supported by results of the WHO Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) aggregate level analyses which found that increasing energy supply is closely associated with the increase in overweight and obesity in European countries [
45].
As a main source of dietary energy, carbohydrate plays a critical role in the Chinese traditional diet. The decrease in carbohydrate observed in our study can partly be explained by the drop in energy expenditure as sedentary behaviors is ubiquitous in daily lives of modern Chinese women. Previous research shows that carbohydrate might promote the development of small intestinal bacterial overgrowth in obesity [
46]. Some arguing that carbohydrate intake has a more prominent role in promoting weight gain than dietary fat [
47]. Our results suggest that overweight/obese individuals were reported consuming a somewhat larger fat but smaller carbohydrate, compared with underweight/normal weight individuals, indicated that increasing trends in energy consumption are of concern for all BMI classes, especially for individuals in the highest BMI classes. Moreover, urban movement has had a significant effect on the amount and type of food produced and consumed in China. For example, agriculture’s share of the economy has continued to decrease since 1970; replaced by livestock, fisheries, and other commodities. This has led to modifications in the ‘traditional’ Chinese diet; increasing the fat intake and decreasing the carbohydrates usually found in the Chinese diets.
A dramatic decline was observed regarding the consumption of total protein in adult female diets, supported by a previous study which showed a slow decrease in protein intake in women between 1997 and 2011. The reasons for the decline in protein intake are difficult to identify and can only be speculated. For instance, a potential explanation may be due to significantly reduced plant sources (rice and pulses) food. Future efforts are needed to explore the other impassible reasons. Our study indicate overweight/obesity females intake the most protein, consistent with the results of a systematic review and meta-analysis, conducted to assess the benefits and harms of higher-protein compared with lower-protein diets in the general population and find that higher-protein diets probably improve adiposity [
48].
The present study indicates that the total energy intakes derived from fat, carbohydrate and protein among females in the 2015 CHNS were 35.7%, 51.6% and 12.6%, respectively. The Chinese dietary guideline (CDG) of 2016 version suggested for Chinese adults that the total energy derived from fat, carbohydrate and protein were below 30%, 55–65% and 10–15%, respectively. The proportion of total energy from protein is in line with the CDG recommendation, the proportion of total energy from carbohydrate below the recommendation. While the energy from fat exceeded the recommendation. Moreover, the proportion of women consuming a diet with more than 30% of total energy from fat more than doubled from 1991 to 2015 (nearly 67%). Excessive fat intake may lead to the development of NCD and chronic condition. Accordingly, the Chinese government need to take immediate actions to carry out effective interventions to promote a healthy diet for Chinese women, considering a rapid acceleration of nutrition and epidemiological transition with increased burden of NCD.
The global prevalence of overweight and obesity as a public health concern is well established and reflects the overall worldwide lack of success in achieving and maintaining a healthy body weight [
49]. Increasing evidence showed that the prevalence of overweight and obesity has increased dramatically over the past decades in China [
50]. In contrast, the importance of gender as a variable in obesity is less well appreciated. Obesity may cause greater harms to females, lead to reproductive endocrine disorders, breast cancer, menstrual disorders, abortion, and so on. Our study found time trends in energy and macronutrient intakes were similar across all three BMI categories. From1991 to 2015, overweight or obesity rates in China’s adult females have risen steadily, with the average rate at 45.4% in 2015. It can be predicted that the burden of diseases caused by obesity of female will increase greatly in China in the future. There for women themselves should have a balanced dietary pattern and healthy lifestyle which they can hold up as an example to their children, which would help prevent the vicious cycle of inter-generational obesity. Efforts should be made to help Chinese women to develop a healthy lifestyle and adopt healthy dietary habits from an early age.
It is worth our attention that by 2015, total energy intake and energy composition of adult women in two age groups is basically consistent. However, the average BMI of women aged 50–64 is significantly higher than that of women aged 18–49. Our research results indicated that overweight and obese women might closely related to energy consumption. Growth with age, activities and hormone levels of women usually significant changes. The relationships between the energy consumption difference and overweight and obesity among women in different age groups will be further discussed in our next research.
Major strengths of this study include the use of the longitudinal data (CHNS) with the latest (2015) and large sample size. The use of individual, consecutive three-day recall method could improve the accuracy of dietary recalls and hence the analysis and results. Moreover, examining this issue in prospective studies that repeatedly collect both dietary intake and body weight data may provide further insight. Our results also highlight several other demographic and lifestyle trends in the Chinese females over the covered time period.
In evaluation of the results, mentioning some limitations seems necessary. As with other population research, dietary data were collected using three consecutive 24-h dietary recalls, which might have relatively limited corrections for within-subject variations compared to non-consecutive 24-h-recalls. However, the average intake over three days can offer a relatively valid estimate of nutrient intakes, as shown in an earlier study using the CHNS. Moreover, macronutrient groups exist in different foods, pointing out to these imbalances makes it impossible to consider which food exactly causes the mentioned deficiency. In addition, the CHNS does not present national data and the vast, western areas of China were not included in the present study.