**1. Introduction**

The hookah, also known as a water pipe, narghile, arghile, or shisha, was invented in the 16th century as an attempt to purify smoke through water [1]. Nowadays hookah smoking is becoming popular in developing countries as well as in Western countries, especially among the young [2–4]. In fact, many hookah smokers consider this practice less harmful than smoking cigarettes because of the misconception that inhaling smoke containing fruit flavours, (i.e., apple, orange, grapes, etc.) through hookah water is less toxic [5]. Strong evidence supports the association between hookah smoking and several chronic diseases as well as a high risk of cancer [6–14] to the extent where it is considered a serious public health problem. This caused the American Heart Association to issue a scientific statement on hookah smoking and the increased risk of cardiovascular disease [15].

On the other hand, obesity is another increasing health problem. It is becoming one of the most serious conditions worldwide, known to be associated with several comorbidities that lead to an increase in disability, morbidity, and mortality [16–21]. Recently, reputable magazine reports have mentioned a potential association between obesity and hookah smoking; however, this is still uncertain [22]. Moreover, to the best of our knowledge, no systematic review considering this issue as a primary outcome has ye<sup>t</sup> been conducted in order to provide a valid interpretation of the evidence published to date based on a systematic review and a meta-analysis. In light of these considerations, we hypothesised an association between hookah smoking and a higher risk of obesity and aimed to systematically review the published literature on this topic in accordance with the PICO process [23], as detailed below:

P—Population: adolescents and adults of both genders [24]; I—Intervention: active hookah smoking; C—Comparison: hookah-smoking group vs. nonsmoking group (when available) or hookah-smoking group vs. cigarette-smoking group (when available); and O—Outcome: obesity, however defined, based on international guidelines, (e.g., BMI, BMI percentiles, waist circumference, body fat percentage, etc.).
