Background: Tailored advice to individuals or groups achieves better weight loss outcomes than generalised advice alone. The literature suggests a profound impact of gender on weight loss processes and outcomes, as a result of physiological and socio-psychological differences between men and women. Diets without defined energy restriction allow a more meaningful comparison of group differences and thus analysis examined gender differences reported in weight loss clinical trials that employed an ad libitum Mediterranean diet approach.
Methods: Three databases (Medline, Embase, Cochrane Central) were systematically searched to retrieve relevant clinical trials for screening by two independent reviewers. Eligibility criteria for title and abstract included: (1) adult population with overweight or obesity, (2) both men and women, (3) weight loss outcome, (4) ad libitum Mediterranean diet and control. Final inclusion after review of full texts required a report of weight loss separately for each gender (with or without supporting data).
Results: Of 34 studies screened, 17 were duplicates. Of the 17 remaining, only 3 (18%) reported weight loss separately for men and women. 2 of these reported no difference between genders while 1 reported that women lost more weight than men (Shai et al., 2008).
Conclusions: It is alarming that such few papers analysed weight loss by gender despite known physiological differences between men and women, highlighting the importance of gender stratification in future clinical trials. Further research is required to explore whether women lose more weight than men on a Mediterranean diet, perhaps by widening the search to include calorie restriction. This study compliments our previous investigation of calorie-restricted low-carbohydrate diets where greater weight loss was seen in males. Examining gender variations in response to different dietary programs will assist health professionals in better tailoring weight loss advice to their patients in the future.