In addition to diet and exercise, eating within an 8-hour window helped people with obesity lose weight, a randomized trial showed.
Compared with eating over 12-plus hours, those who kept all caloric intake to 8 hours — from 7 a.m. to 3 p.m. — lost an additional 2.3 kg (5.1 lb) over a 14-week study, reported Courtney Peterson, PhD, of the University of Alabama at Birmingham, and colleagues.
This weight loss was equivalent to eating 214 fewer calories per day, they noted in JAMA Internal Medicine.
When the eating time-restricted group received weight-loss treatment (energy restriction), they saw an average drop of 6.3 kg (13.9 lb; P<0.001), while those who underwent energy restriction alone saw a weight loss of 4.0 kg (8.8 lb; P<0.001).
The 8-hour eating window wasn’t much help for shedding body fat specifically. While this group saw slightly more body fat loss (-1.4 kg/-3.1 lb), it wasn’t significantly more than with the calorie-restricted diet alone. Likewise, there wasn’t a significant difference seen in the ratio of fat loss to weight loss (-4.2%).
However, in a secondary analysis of the 59 participants who finished the 14-week trial, the 8-hour eating window did prove to be more effective for shedding body fat (-1.8 kg [-4.0 lb], 95% CI -3.6 to 0.0 kg, P=0.047) and trunk fat (-1.2 kg [-2.6 lb], 95% CI -2.2 to -0.1 kg, P=0.03).
Adding the eating time-restricted window to dieting also dropped diastolic blood pressure (-4 mm Hg, 95% CI -8 to 0 mm Hg, P=0.04), though this was the only cardiometabolic risk factor that seemed to improve with time-restriction. It also bettered some mood and sleep parameters, including mood subscores for vigor-activity, fatigue-inertia, and depression-dejection.
“Our data suggest that early time-restricted eating is feasible, as participants adhered 6.0 days per week on average, and most participants adhered at least 5 days per week,” Peterson’s group pointed out.
In an accompanying commentary, Shalender Bhasin, MB, BS, of Brigham and Women’s Hospital in Boston, was quick to compare this trial to another recent time-restricted trial published earlier this year in the New England Journal of Medicine.
Following a similar methodology, that trial found that following a time-restricted diet in addition to calorie restriction did not result in a significantly greater amount of weight loss compared with a calorie-restricted diet alone (-1.8 kg [-4.0 lb] difference; P=0.11).
One key difference between the two trials included the earlier 8-hour timeframe in the current study (7 a.m. to 3 p.m. vs 8 a.m. to 4 p.m.). Bhasin noted that another difference was that the previous trial didn’t set a specific window for the comparator group, whereas Peterson’s group instructed the other group to eat over a timeframe of 12 or more hours each day. The current trial was also only 14 weeks in duration versus 1 year for the prior trial.
Regardless of these differences, Bhasin said both trials did see “high levels of adherence with dietary prescriptions,” which might be hard to achieve outside of a trial setting and in a clinical setting.
“The scientific premise and the preclinical data of the effects of time-restricted eating are promising, but the inconsistency among studies renders it difficult to draw strong inferences from these well-conducted but relatively small trials,” said Bhasin.
For this study, Peterson and team randomized 90 adults (mean age 43 years, 80% women) with a BMI of 30 to 60 into each of the two groups. All participants received weight-loss counseling involving energy restriction at the UAB Weight Loss Medicine Clinic, and followed a calorie-restricted diet of 500 calories per day below their resting energy expenditure and exercised for 75 to 150 minutes per week, depending on their baseline physical activity.
This study was supported by grants from the National Center for Advancing Translational Sciences and from the National Institute of Diabetes and Digestive and Kidney Diseases.
Peterson and co-authors reported relationships with the NIH, Wondr Health, and Pennington Biomedical Research Center/Louisiana State University.
Bhasin reported relationships with AbbVie, MIB, OPKO Health, Aditum, FPT, and XYOne.