Weight Regain Reverses Caloric Restriction-Induced Benefits on the Insulin-IGF-1 Nutrient-Sensing Pathway: Post Hoc Analysis From the CALERIE-2 Randomized Controlled Trial.

OBJECTIVE: To investigate the long-term metabolic and hormonal consequences of sustained weight loss versus weight regain after 1 year of caloric restriction (CR), with attention to insulin resistance and type 2 diabetes risk.
RESEARCH DESIGN AND METHODS: In the 2-year Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy 2 (CALERIE-2) trial (n = 220), participants were randomized to 25% CR or control diet. The intervention targeted weight loss over the first 6-12 months, followed by a 12-month maintenance phase. To assess weight-regain consequences, participants were stratified by weight trajectory regardless of randomization, and group differences were balanced by propensity score weighting. Cardiometabolic and hormonal markers of available participants (n = 190), as well as a biomarker-based estimate of biological age, were compared across weight trajectory groups.
RESULTS: At 12 months, weight loss ranged from 5.0 to 5.8 kg between groups. Between months 12 and 24, most participants either maintained weight (n = 112) or continued to lose weight (n = 58), whereas a smaller group regained >5% of baseline weight (n = 20). This group had the largest initial caloric reductions. Weight regain reversed improvements in insulin area under the curve and the ratio of insulin-like growth factor 1 (IGF-1) to insulin-like growth factor-binding protein 1, and sustained weight loss maintained metabolic benefits and was associated with greater reductions in biological age.
CONCLUSIONS: Substantial weight loss followed by weight regain can attenuate or reverse CR-induced benefits on key regulators of the insulin-IGF-1 nutrient-sensing pathway and markers of biological aging. Sustained, moderate weight loss more effectively improves insulin resistance and maintains favorable hormonal profiles linked to type 2 diabetes risk and aging biology.