Behavioral mediators of weight loss in the SHED-IT community randomized controlled trial for overweight and obese men

Background: Little is known about which behavioral strategies are most important to target in weight loss interventions for men. Purpose: The aim of the current study was to identify behavioral mediators of weight loss in the male-only Self-Help, Exercise, and Diet using Information Technology (SHED-IT) community weight loss study. Methods: A randomized controlled trial with 159 overweight/obese men [mean (SD) age = 47.5 (11.0) years; body mass index = 32.7 (3.5) kg/m²] assessed at baseline, 3 months (post-test) and 6 months (follow-up). Results: In an intention-to-treat, multiple-mediator model, the significant intervention effect on weight at 6 months (-3.70 kg; p < 0.001) was mediated by increases in physical activity (steps/day) and decreases in takeaway meals (kJ/day) and portion size at 3 months. The largest mediation effect was for physical activity (-0.6 kg; 95% confidence interval -1.4, -0.1). Overall, the targeted mediators accounted for 47.0% of the intervention's effect on weight. Conclusion: Step counts, takeaway food consumption, and portion sizes may be key areas to target in future weight loss programs for men (ACTRN12610000699066).