Time-Restricted Eating Without Exercise Enhances Anaerobic Power and Reduces Body Weight: A Randomized Crossover Trial in Untrained Adults

<b>Background</b>: Time-restricted eating (TRE), a dietary strategy that confines daily food intake to specific time windows, has been shown in animal models to enhance physical performance even without exercise training. However, evidence in humans under non-exercise conditions remains limited. <b>Objective</b>: This study aimed to investigate the effects of early TRE (eTRE; 08:00-14:00) and delayed TRE (dTRE; 12:00-18:00) on body weight, aerobic endurance, and anaerobic power in untrained adults. <b>Methods</b>: In a randomized crossover trial, 28 healthy university students (mean age 23.47 ± 2.87 years; 16 women) completed two 4-week interventions, eTRE and dTRE, separated by a 2-week washout. Participants did not engage in any structured exercise during the intervention period. Body weight, aerobic endurance (cycling time to exhaustion at a fixed workload), and anaerobic power (peak power output during sprint cycling) were assessed after each phase. <b>Results</b>: Body weight significantly decreased after eTRE (-1.56 kg; 95% CI [-2.07, -1.05]; <i>p</i> < 0.001; Cohen's dz = 1.17) and dTRE (-0.61 kg; 95% CI [-1.12, -0.10]; <i>p</i> = 0.022; Cohen's dz = 0.55), with a greater reduction observed in eTRE compared to dTRE (-0.95 kg; 95% CI [-1.74, -0.16]; <i>p</i> = 0.020). Aerobic endurance showed no significant change across phases (all <i>p</i> > 0.05). Anaerobic power significantly improved after both eTRE (+21.25 W; 95% CI [12.03, 30.47]; <i>p</i> < 0.001; Cohen's dz = 1.10) and dTRE (+35.43 W; 95% CI [26.21, 44.65]; <i>p</i> < 0.001; Cohen's dz = 1.20), and the improvement was significantly greater in dTRE compared to eTRE (+14.18 W; 95% CI [1.79, 26.57]; <i>p</i> = 0.025; Cohen's dz = 0.54). <b>Conclusions</b>: Both early and delayed TRE independently led to weight loss and enhanced anaerobic power in the absence of an exercise intervention. eTRE was more effective for weight reduction, whereas dTRE produced greater improvements in anaerobic performance.