Background: It is well established that tailored advice achieves better weight loss outcomes. Previous research suggests a profound effect of gender on weight loss processes and outcomes due to physiological and socio-psychological differences between men and women, suggesting that tailoring advice on the basis of gender is warranted. This analysis examined reported gender differences in large clinical trials using a low-carbohydrate diet approach.
Methods: The Ovid Medline database was searched to retrieve studies of low-carbohydrate diets for screening by two reviewers. Eligibility criteria included: (1) controlled trial design, (2) adult population of men and women aged 18+ years with overweight or obesity, (3) weight loss outcome, (4) sample size > 100, (5) diet control. Final inclusion required a report of weight loss on the basis of gender.
Results: Of 441 studies screened, 71 trials were appropriate but only 12 reported weight loss (%) on the basis of gender. Of these studies, 2 reported no difference in weight loss by gender. 10 mentioned a difference, with 8 specifically reporting that men lost more weight on a low-carbohydrate diet. One study reported a marked weight loss for women, and another that women lost more weight on a Mediterranean rather than low-carbohydrate diet.
Conclusions: To our concern, very few studies analysed weight loss by gender despite distinct known differences between men and women. Interestingly when a difference was found, men tended to lose more weight than women on a low-carbohydrate diet. Other weight loss regimes and defining variables will be examined and findings from such analyses may assist health professionals in better tailoring advice to their patients. Importantly, this study highlights a need for gender stratification of analysis in future weight loss trials, since failure to do so may mask potential differences that could be of important clinical relevance.