Early Time-Restricted Eating Effective for Weight Loss in Patients with Obesity

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Early time-restricted eating was more effective for losing weight than eating over a window of ≥12 hours, but did not affect body fat.

New findings determined that practicing time-restricted eating (TRE) by eating early in the day (eTRE) was more effective for weight loss than eating over a window of 12 or more hours in adults with obesity.

Relative to the control eating group, the eTRE plus energy restriction trial group lost an additional 2.3 kg, an approximate 50% improvement in weight loss.

Study author Courtney M. Peterson, PhD, University of Alabama at Birmingham and colleagues noted that eTRE is both feasible, with participants averaging 6.0 days per week on average and may lead to greater improvements in mood, which may benefit adherence.

“It also improves mood by decreasing fatigue and feelings of depression-dejection and increasing vigor, and those who can stick with eTRE lose more body fat and trunk fat,” Peterson wrote. “However, eTRE did not affect most fasting cardiometabolic risk factors in the main intention-to-treat analysis.”

To determine the efficacy of eTRE on weight loss and cardiometabolic health, investigators conducted the 14-week, parallel-arm trial between August 2018 - April 2020. They included new patients with obesity at the Weight Loss Medicine Clinic of the University of Alabama at Birmingham (UAB) Hospital. Eligible patients were 25 - 75 years old, had a body mass index (BMI) between 30.0 and 60.0, and were not diabetic or had a severe or unstable chronic medical condition.

They were randomized to follow low eTRE with an 8-hour eating window between 7:00 and 15:00 or a control eating schedule with a self-selected ≥12-hour window designed to mimic US median meal filming habits, noted the investigators. All received weight-loss treatment with energy restriction.

The study enrolled 90 participants (72 [80%] female), with a mean BMI of 39.6 and mean age of 43 years. The findings suggest the eTRE + ER group adhered to a mean of 6.0 days per week, which was lower than the control + ER group (6.3 days per week; P = .03).

Both study groups achieved clinically meaningful weight loss (-6.3 kg vs -4.0 kg), but the eTRE + ER intervention was more effective for weight loss, losing an additional 2.3 kg (95% confidence interval [CI], -3.7 to -0.9 kg; P = .002).

However, investigators noted there was no statistically significant differences in absolute fat loss (-1.4 kg; 95% CI, -2.9 to 0.2 kg; P = .09) or the ratio of fat loss to weight loss (n = 41; -4.2%; 95% CI, -14.9 to 6.5%; P = .43).

Moreover, the eTRE+ER intervention lowered diastolic blood pressure by an additional 4 mm Hg (95% CI, -8 to 0 mm Hg; P = .04) relative to CON+ER. The effects of eTRE+ER were equivalent to reducing calorie intake by an additional 214 kcal/d.

The intervention was additionally more effective at improving total mood disturbances, including fatigue-inertia, depression-dejection, and vigor-activity. All other cardiometabolic risk factors, food intake, physical activity, and sleep outcomes were similar between groups, reported the investigators.

In invited commentary, Shalender Bhasin, MB, BS, Harvard Medical School, noted the limitations of this study’s findings, including a lack of clarity on whether TRE late in the day is deleterious and a lack of generalization to those with cardiometabolic disorders.

“Substantially larger randomized clinical trials of longer duration are needed to comprehensively evaluate the hypothesized benefits and risks of long-term TRE of calorically restricted diets in adults,” Bhasin said. “For now, TRE is a promising idea in need of stronger clinical trial evidence to support its benefits and long-term safety.”

The study, “Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial,” was published in JAMA Internal Medicine.