Effect of a Lifestyle Intervention on Cardiometabolic Health Among Emerging Adults: A Randomized Clinical Trial

ImportanceThe prevalence of obesity has increased substantially among emerging adults, yet no previous large-scale behavioral weight loss trials have been conducted among this age group.ObjectiveTo test the effect of 2 theory-based motivational enhancements on weight loss within a primarily digital lifestyle intervention designed for emerging adults.Design, Setting, and ParticipantsIn this randomized clinical trial conducted at an academic medical research center, 382 participants aged 18 to 25 years with a body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) of 25 to 45 were enrolled between February 2, 2016, and February 6, 2019. Data collection was completed February 8, 2020. Analysis was performed on an intention-to-treat basis.InterventionsParticipants were randomized to 1 of 3 groups: developmentally adapted behavioral weight loss (aBWL), aBWL plus behavioral economics (aBWL + BE), or aBWL plus self-determination theory (aBWL + SDT). All groups received a 6-month intervention with 1 group session, 1 individual session, and a digital platform (digital tools for self-monitoring, weekly lessons, tailored feedback, text messages, and optional social media). The aBWL + BE group received modest financial incentives for self-monitoring and weight loss; the aBWL + SDT group received optional experiential classes. Coaching and message framing varied by group.Main Outcomes and MeasuresThe primary outcome was mean (SE) weight change (in kilograms) at 6 months. Secondary outcomes included proportion of participants achieving weight loss of 5% or more, percentage weight change, waist circumference, body composition, and blood pressure.ResultsAmong the 382 participants (mean [SD] age, 21.9 [2.2] years), 316 (82.7%) were female, mean (SD) BMI was 33.5 (4.9), 222 (58.1%) were of underrepresented race and/or ethnicity, and 320 (83.8%) were retained at the primary end point. There was a significant time effect for mean (SE) weight loss (−3.22 [0.55] kg in the aBWL group; −3.47 [0.55] kg in the aBWL + BE group; and −3.40 [0.53] kg in the aBWL + SDT group; allP < .001), but no between-group differences were observed (aBWL vs aBWL + BE: difference, −0.25 kg [95% CI, −1.79 to 1.29 kg];P = .75; aBWL vs aBWL + SDT: difference, −0.18 kg [95% CI, −1.67 to 1.31 kg];P = .81; and aBWL + SDT vs aBWL + BE: difference, 0.07 kg [95% CI, −1.45 to 1.59 kg];P = .93). The proportion of participants achieving a weight loss of 5% or more was 40.0% i