Data from a 14-week randomized clinical trial suggests adherence to a time-restricted diet was associated with significant differences in weight loss and improvements in blood pressure compared to a typical diet.
New research suggests a weight loss strategy leveraging a time-restricted eating (TRE) approach that focuses on eating early in the day, could be an effective strategy for overall weight loss as well as improved fat loss and cardiometabolic health.
A 14-week, parallel-arm trial comparing the effects of a TRE approach against a control diet, the results of the randomized clinical trial demonstrate adherence to a TRE diet was a more effective strategy for reducing body weight and improving diastolic blood pressure.
“The key finding of this study is that eTRE was more effective for losing weight than eating over a period of 12 or more hours. In our trial, the eTRE group lost an additional 2.3 kg relative to the control group, an approximately 50% improvement in weight loss. For comparison, prior studies are about evenly divided on whether TRE reduces body weight and are mixed for body fat, while studies that shift food intake to the morning and/or earlier in the daytime have more consistently reported weight loss,” wrote investigators.
Led by investigators at the University of Alabama at Birmingham, the present trial with the intent of assessing the effect of TRE in overweight adults. Conducted from 2018-2020, investigators designed their trial as a parallel-arm, randomized clinical trial and enrolled patients aged 26-75 years with obesity who received weight loss treatment through the Weight Loss Medicine Clinic at the University of Alabama at Birmingham Hospital. Specific inclusion criteria for the trial required patients to have a BMI between 30-60 kg/m2 and not to have diabetes or a severe or unstable chronic medical condition at baseline.
The trial randomized patients to follow a TRE regimen consisting of an 8-hour eating window between 7:00 and 15:00 every day or a control diet consisting of a self-selected eating window of 12 hours or greater, which was designed to mimic US median meal timing habits. Participants were instructed to follow their assigned eating regimens at least 6 days per week.
The coprimary outcomes of interest for the trial were weight loss and fat loss. Secondary outcomes of interest included changes in blood pressure, heart rate, glucose levels, insulin levels, and plasma lipid levels between the study arms. As part of the trial protocol, all participants received weight loss counseling at the University of Alabama Weight Loss Medicine Clinic. Investigators pointed out randomization was performed in a 1:1 ratio, with stratification based on sex, race, and baseline physical activity level.
A total of 90 participants were ultimately identified for inclusion in the trial and underwent enrollment. This cohort had. Mean BMI of 39.6 (SD, 6.7) kg/m2, a mean age of 43 (SD, 11) years, and 80% were female. Initial analysis indicated the TRE group adhered to the recommended eating window 6.0 (SD, 0.8) days per week.
Further analysis suggested adherence to the TRE regimen was a more effective approach for weight loss, but no significant difference was observed for body fat (-1.4 kg [95% CI, -2.9 to 0.2 kg]; P=.09) or the ratio of fat loss to weight loss (-4.2% [95% CI, -14.9 to 6.5%]; P=.43). Investigators pointed out the effects of the TRE approach were equivalent to reducing caloric intake by an additional 214 calories per day.
In analyses of secondary outcomes, results suggested adherence to the TRE regimen was associated with o improved diastolic blood pressure (−4 mmHg [95% CI, −8 to 0 mmHg]; P=.04) and mood disturbances, including fatigue-inertia, vigor-activity, and depression-dejection, but other secondary outcomes, including other cardiometabolic risk factors, food intake, physical activity, and sleep outcomes, were similar between groups. Investigators pointed out an analysis of the 59 participants who completed the trial indicated TRE was more effective for losing body fat and trunk fat than the control diet.
In an editorial comment published in JAMA Internal Medicine, Shalender Bhasin, MBBS, professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, underlined the importance of the current trial’s findings related to the growing knowledge base surrounding TRE as an approach to obesity or weight loss management, but cautioned further work is needed to understand the effects of TRE.
“The scientific premise and the preclinical data of the effects of TRE are promising, but the inconsistency among studies renders it difficult to draw strong inferences from these well-conducted but relatively small trials. Despite limited evidence of its safety and efficacy, TRE as a fad has spread rapidly to millions of enthusiasts worldwide,” wrote. “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. For now, TRE is a promising idea in need of stronger clinical trial evidence to support its benefits and long-term safety.”
This study, “Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity,” was published JAMA Internal Medicine.