Fun For Wellness (FFW) is an online behavioral intervention developed to promote well-being by enhancing the self-efficacy of participants. The objective of this study was to evaluate the effectiveness of FFW to promote health in adults with obesity in the United States in a relatively uncontrolled setting. The study design was a large-scale, prospective, double-blind, parallel group randomized controlled trial. Data collection occurred at three time points: baseline, 30 days, and 60 days after baseline. There was evidence for a positive direct effect of FFW on physical health status ([Formula: see text] = 1.33, p = .005, d = 0.24) at 60 days after baseline. In addition, there was evidence of a positive indirect effect of FFW on mental health status at 60 days after baseline through psychological well-being self-efficacy ([Formula: see text] = 0.44, [0.05, 0.94]).
