Fasting by the Clock: A Randomized Comparison of 12:12, 14:10 and 16:8 Time-Restricted Eating for Weight and Metabolic Outcomes in Adults With Overweight or Obesity

Background: Time-restricted eating (TRE) is increasingly used for weight management, but the optimal daily fasting duration remains uncertain, particularly in Indian adults with overweight or obesity. Objective: To compare the effects of 12:12, 14:10 and 16:8 TRE regimens on weight reduction and metabolic outcomes. Methods: This prospective randomized three-arm study included 186 adults with BMI 25.0–39.9 kg/m² at Pushpagiri Medical Institute of Medical Sciences and Research Centre from November 2025 to April 2026. Participants were allocated equally to 12:12, 14:10 or 16:8 TRE and followed for 12 weeks with standardized dietary and physical-activity advice. Results: Baseline characteristics were comparable. Mean percentage weight loss was 3.9±1.8%, 6.1±2.1% and 7.5±2.3% in the 12:12, 14:10 and 16:8 groups, respectively (p<0.001). Achievement of ≥5% weight loss occurred in 29.0%, 58.1% and 72.6% of participants, respectively (p<0.001). Reductions in BMI, waist circumference, body-fat percentage, fasting glucose and HbA1c were greatest with 16:8 TRE. Adherence declined with longer fasting duration, while adverse events were infrequent and comparable. Conclusion: Longer daily fasting produced greater short-term weight and metabolic improvements, although 14:10 may offer a favorable balance between efficacy and adherence. These findings support individualized selection of TRE schedules according to desired weight loss, metabolic benefit, tolerability, and capacity for sustained adherence in practice. Keywords: Intermittent fasting; Metabolic health; Obesity; Time-restricted eating; Weight reduction.