Effect of Time-Restricted Eating on Metabolic Adaptation in Adults With Severe Obesity During Early Phase of Weight...

To compare metabolic adaptations at the early phase of weight loss in individuals with severe obesity assigned to two strategies of energy restriction: continuous or in combination with time-restricted eating (TRE).

100 participants (> 40 kg/m²; 20-60 years) were randomized into two groups: continuous energy restriction (CER, n = 42) and TRE combined with energy restriction (TRE + ER; eating window: 10am-6pm). Resting metabolic rate (RMR) by indirect calorimetry, body composition by dual-energy X-ray absorptiometry (DXA), serum hormones, and appetite feelings were evaluated at baseline and after 1 week of prescribed diet at 60% the total energy expenditure. Early adaptive thermogenesis (AT) was calculated using measured and predicted RMR. Data were evaluated using ANCOVA and linear mixed-effects model.

After adjustment for RMR at baseline and body composition, RMR after 1 week was similar between groups (β_group = 47 ± 32 kcal/day; p = 0.148). Early AT was significantly lower in the TRE + ER group (-13 ± 160 kcal vs. -83 ± 150 kcal; p = 0.038). After a week of energy restriction, leptin, insulin, and TSH concentrations decreased in both groups (time effect, p < 0.05) with no group x time interaction. The feeling of hunger increased after 1 week only in the CER group (p = 0.048).

Results suggest that TRE modestly attenuate early AT, but this effect does not translate into differences in RMR after 1 week. Hormonal and appetite responses were also not substantially affected by TRE. Further studies are needed to determine whether the modest early effects of TRE translate into clinically meaningful long-term benefits for weight management.