Weight cycling in women: A challenge for cardiometabolic health, not for brown fat

Abstract

Body weight cycling (BWC) consists of repeated episodes of intentional weight loss followed by unintentional regain, which has been associated with adverse metabolic and body composition changes. In animal models, reduced energy expenditure may also contribute to brown adipose tissue (BAT) loss. Thus, we hypothesize that BWC in humans associates with reduced BAT activity. We explored associations between BWC, cold-induced BAT activity and cardiometabolic health. This cross-sectional study included 121 women (aged 20-41 years; body mass index: 18.9-52.3 kg/m²). Participants were classified as noncyclers or cyclers based on self-reported BWC history (≥3 episodes of intentional weight loss and regain of ≥4.5 kg over the past 4 years). Anthropometric and biochemical parameters were assessed, and visceral adipose tissue and body fat percentages (%BF) were evaluated using dual-energy X-ray absorptiometry (DXA). BAT activity was assessed using infrared thermography of the supraclavicular region at 15-minute intervals over a 2-hour period, and the maximum temperature reached during cold exposure was considered as BAT activity parameter. A total of 92 participants were classified as cyclers, exhibiting higher body adiposity and a more unfavorable metabolic profile than noncyclers. BWC emerged as a negative predictor of BAT activity (β = −0.34; P = .008), but this effect was completely mediated by %BF, rendering the direct association nonsignificant (β = −0.086; P = .539). These findings suggest the effect of BWC history on BAT activity was fully mediated by %BF. Clinically, this implies that therapies targeting BAT activity should also address overall adiposity in individuals with obesity, irrespective of prior weight-cycling history.