Gender differences in response to an opportunistic brief intervention for obesity in primary care: data from the BWeL trial

Weight loss programmes appeal mainly to women, prompting calls for gender-specific programmes. In the United Kingdom, general practitioners (GPs) refer nine times as many women as men to community weight loss programmes. GPs endorsement and offering programmes systematically could reduce this imbalance. In this trial, consecutively attending patients in primary care with obesity were invited and 1882 were enrolled and randomized to one of two opportunistic 30-second interventions to support weight loss given by GPs in consultations unrelated to weight. In the support arm, clinicians endorsed and offered referral to a weight loss programme and, in the advice arm, advised that weight loss would improve health. Generalized linear mixed effects models examined whether gender moderated the intervention. Men took effective weight loss action less often in both arms (support: 41.6% vs 60.7%; advice: 12.1% vs 18.3%; odds ratio (OR) = 0.38, 95% confidence interval (CI), 0.27, 0.52, P < .001) but there was no evidence that the relative effect differed by gender (interaction P = .32). In the support arm, men accepted referral and attended referral less often, 69.3% vs 82.4%; OR = 0.48, 95% CI, 0.35, 0.66, P < .001 and 30.4% vs 47.6%; OR = 0.48, 95% CI, 0.36, 0.63, P < .001, respectively. Nevertheless, the gender balance in attending weight loss programmes closed to 1.6:1. Men and women attended the same number of sessions (9.7 vs 9.1 sessions, P = .16) and there was no evidence weight loss differed by gender (6.05 kg men vs 4.37 kg women, P = .39). Clinician-delivered opportunistic 30-second interventions benefits men and women equally and reduce most of the gender imbalance in attending weight loss programmes.