Abstract 13507: The Role of Weight Loss in Mediating the Effects of a 2-year Caloric Restriction Regimen on Cardiometabolic Risk Markers in Individuals Without Obesity

Abstract

Introduction: Caloric restriction (CR) improves cardiometabolic risk, even among individuals without obesity. However, it is unclear whether these aging-related benefits are mediated by weight loss. Mediation analyses inform mechanisms underlying relationships between an exposure and outcome. Using mediation analyses, our aim was to test if 2-year weight loss mediates the beneficial effects of CR on cardiometabolic risk markers in individuals without obesity. Methods: Participants without obesity were randomized 2:1 to CR or ad libitum (AL) as part of the 2-year trial, Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE). The CR group aimed to enact 25% CR for 2 years, while AL maintained habitual energy intake. Baseline and year 2 assessments included weight and cardiometabolic risk markers. Using the approaches of Valeri and VanderWeele, mediation was quantified as the natural indirect effect (NIE), defined as the impact of an exposure on an outcome through a mediator. Here, the NIE was the effect of CR (exposure) on cardiometabolic risk markers (outcome) that was accounted for by weight change (mediator). Results: In total, 117 and 71 participants in the CR and AL groups, respectively, completed the trial. The CR group achieved 11.9 (± 0.7)% CR and 7.6 (± 0.3) kg of weight loss ( P < 0.01 versus AL). Weight loss significantly mediated the CR-induced improvements in total cholesterol (NIE = -10.4 ± 3.5 mg/dL), low-density lipoprotein cholesterol (NIE = -8.5 ± 2.8 mg/dL), high-density lipoprotein cholesterol (NIE = 2.9 ± 1.3 mg/dL), triglycerides (NIE = -0.20 ± 0.05 log mg/dL), the homeostatic model assessment of insulin resistance (NIE = -0.22 ± 0.06), and C-reactive protein (NIE = -0.39 ± 0.15 log ug/mL) ( P ≤ 0.02). Weight loss did not mediate CR-induced reductions in systolic (NIE = -0.9 ± 1.4 mmHg) and diastolic (NIE = -1.0 ± 1.1 mmHg) blood pressure ( P ≥ 0.37). Conclusion: In individuals without obesity, CR-induced improvements in multiple cardiometabolic risk markers are driven by weight loss after 2 years. These findings emphasize that, even in individuals without obesity, weight loss after prolonged CR plays a role in improving cardiometabolic disease risk; however, some CR benefits still occur independent of weight loss.