Mediators of weight change in underserved patients with obesity: exploratory analyses from the Promoting Successful Weight Loss in Primary Care in Louisiana (PROPEL) cluster-randomized trial

Abstract

Intensive lifestyle interventions (ILIs) stimulate weight loss in underserved patients with obesity, but the mediators of weight change are unknown. We aimed to identify the mediators of weight change during an ILI compared with usual care (UC) in underserved patients with obesity. The PROPEL (Promoting Successful Weight Loss in Primary Care in Louisiana) trial randomly assigned 18 clinics (n=803) to either an ILI or UC for 24 mo. The ILI group received an intensive lifestyle program; the UC group had routine care. Body weight was measured; further, eating behaviors (restraint, disinhibition), dietary intake (percentage fat intake, fruit and vegetable intake), physical activity, and weight- and health-related quality of life constructs were measured through questionnaires. Mediation analyses assessed whether questionnaire variables explained between-group variations in weight change during 2 periods: baseline to month 12 (n=779) and month 12 to month 24 (n=767). The ILI induced greater weight loss at month 12 compared with UC (between-group difference: -7.19kg; 95% CI: -8.43, -6.07kg). Improvements in disinhibition (-0.33kg; 95% CI: -0.55, -0.10kg), percentage fat intake (-0.25kg; 95% CI: -0.50, -0.01kg), physical activity (-0.26kg; 95% CI: -0.41, -0.09kg), and subjective fatigue (-0.28kg; 95% CI: -0.46, -0.10kg) at month 6 during the ILI partially explained this between-group difference. Greater weight loss occurred in the ILI at month 24, yet the ILI group gained 2.24kg (95% CI: 1.32, 3.26kg) compared with UC from month 12 to month 24. Change in fruit and vegetable intake (0.13kg; 95% CI: 0.05, 0.21kg) partially explained this response, and no variables attenuated the weight regain of the ILI group. In an underserved sample, weight change induced by an ILI compared with UC was mediated by several psychological and behavioral variables. These findings could help refine weight management regimens in underserved patients with obesity.This trial was registered at clinicaltrials.gov as NCT02561221.