Men's Representation in Behavioral Weight Loss Trials: A Systematic Review

BACKGROUND: Historically, men have been underrepresented in behavioral weight loss intervention research, despite facing higher risks for obesity-related diseases. Understanding this underrepresentation is critical for designing weight loss interventions that are both inclusive and effective. OBJECTIVES: The primary aim of this systematic review is to (1) examine the proportion of men participating in behavioral weight loss trials. Secondary research questions include (2) how often men are targeted as the primary population; (3) whether certain trial characteristics are associated with higher or lower male participation; and (4) in trials where men are underrepresented (< 40% of participants), how often researchers acknowledge this limitation or discuss implications for generalizability. METHODS: A systematic search of SCOPUS, CENTRAL, and MEDLINE was conducted for randomized trials published in English between January 2010 and December 2022. Eligible studies recruited adults (≥ 18 years) into behavioral weight loss interventions using a randomized controlled design. Study characteristics associated with men's participation were examined using t-tests and ANOVAs. RESULTS: Of 57,497 participants across 257 trials, only 30% were men. Overall, 21% of studies recruited women only (n = 54) compared to 5% that recruited men only (n = 14). Men's participation was higher in trials targeting adults with a co-occurring physical condition (36% vs. 28%). Of 189 trials recruiting both men and women, 76% recruited < 40% men, but only one-third of these papers acknowledged this as a limitation. CONCLUSION: Men remain underrepresented in behavioral weight loss trials. To overcome this, strategies to improve men's uptake of existing interventions are needed, alongside the development of codesigned gender-tailored approaches.