Preventing weight gain in adults: A systematic review and meta-analysis of randomized controlled trials.

Weight gain prevention is a global public health priority to address escalating adiposity in adults. This review evaluates the efficacy of weight gain prevention trials targeting adults aged 18-50 years and adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Trials of any duration from inception to May 2020 that evaluated a weight gain prevention intervention (using either prescriptive diet, prescriptive physical activity, prescriptive diet, and/or physical activity or non-prescriptive lifestyle) and included weight or body mass index (weight [kg]/height [m2 ]) were eligible. Twenty-nine trials across 34 publications (participants n = 37,407) were included. Intervention resulted in less weight gain compared with controls (-1.15 kg [95% CI -1.50, -0.80 kg] p < 0.001). Subgroup analysis demonstrated greater effectiveness with prescriptive (-1.60 kg [95% CI -2.00, -1.19] p < 0.001) compared with non-prescriptive (-0.81 kg [95% CI 1.10, -0.53] p < 0.001) intervention types. Interventions had greatest impact in healthy weight (18.5-24.9 kg/m2 ) (-0.82 kg [95% CI -1.5, -0.50] p < 0.001) or overweight (25.0-29.9 kg/m2 ) (-1.48 kg [95% CI -1.85, -1.12] p < 0.001) compared with obese populations (≥30.0 kg/m2 ) (-0.56 kg [95% CI -1.40, 0.27] p = 0.19). These findings demonstrate that lifestyle intervention prevents cumulative weight gain in non-obese adults, with future research required to inform cost-effectiveness and implementation feasibility.