Effect of time restricted eating on body weight and fasting glucose in participants with obesity: results of a randomized, controlled, virtual clinical trial

Background: Time restricted eating (TRE) is an emerging dietary intervention for weight loss that is hypothesized to reinforce the metabolic benefits of nightly fasting/ketosis. This pilot study investigated the effectiveness of a daily 14-h metabolic fast (14:10 TRE beginning after dinner, a "fasting snack" at hour 12, and ending with breakfast 14 h later) combined with a commercial weight management program on body weight and fasting blood glucose (FBG) in individuals with obesity. We also investigated the effect of the low-calorie, high-fat, low-carbohydrate, and low-protein "fasting snack" on blood glucose. Methods: This 8-week, randomized, controlled, clinical trial included men and women (BMI ≥ 30 kg/m²) between June and October 2020. Study procedures were conducted remotely. Participants were randomized to 14:10 or 12-h TRE (12:12, active comparator) and prescribed a diet (controlled for calories and macronutrient composition) and exercise program that included weekly customized counseling and support. The primary outcome was change from baseline in body weight in the 14:10 group. Results: Of the 78 randomized participants, 60 (n = 30/group) completed 8 weeks. The LS mean change from baseline in weight in the 14:10 group was -8.5% (95% CI -9.6 to -7.4; P<0.001) and -7.1% (-8.3 to -5.8; P < 0.001) in the 12:12 group (between group difference -1.4%; -2.7 to -0.2; P<0.05). There was a statistically significant LS mean change from baseline to week 8 in FBG in the 14:10 group of -7.6 mg/dl (95% CI -15.1 to -0.1; P<0.05) but not in the 12:12 group (-3.1 mg/dl, -10.0 to 3.7; P=NS). Both interventions resulted in a larger reduction in FBG in participants with elevated FBG (≥100 mg/dl) at baseline (both P<0.05). Conclusions: In participants with obesity who completed 8 weeks of the 14:10 TRE schedule combined with a commercial weight loss program, there was statistically significant and clinically meaningful weight loss and improvements in FBG.