Importance: The efficacy and safety of time-restricted eating have not been explored in large randomized clinical trials.
Objective: To determine the effect of 16:8-hour time-restricted eating on weight loss and metabolic risk markers.
Interventions: Participants were randomized such that the consistent meal timing (CMT) group was instructed to eat 3 structured meals per day, and the time-restricted eating (TRE) group was instructed to eat ad libitum from 12:00 pm until 8:00 pm and completely abstain from caloric intake from 8:00 pm until 12:00 pm the following day.
Design, Setting, and Participants: This 12-week randomized clinical trial including men and women aged 18 to 64 years with a body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) of 27 to 43 was conducted on a custom mobile study application. Participants received a Bluetooth scale. Participants lived anywhere in the United States, with a subset of 50 participants living near San Francisco, California, who underwent in-person testing.
Main Outcomes and Measures: The primary outcome was weight loss. Secondary outcomes from the in-person cohort included changes in weight, fat mass, lean mass, fasting insulin, fasting glucose, hemoglobin A1c levels, estimated energy intake, total energy expenditure, and resting energy expenditure.
Results: Overall, 116 participants (mean [SD] age, 46.5 [10.5] years; 70 [60.3%] men) were included in the study. There was a significant decrease in weight in the TRE (-0.94 kg; 95% CI, -1.68 to -0.20; P = .01), but no significant change in the CMT group (-0.68 kg; 95% CI, -1.41 to 0.05, P = .07) or between groups (-0.26 kg; 95% CI, -1.30 to 0.78; P = .63). In the in-person cohort (n = 25 TRE, n = 25 CMT), there was a significant within-group decrease in weight in the TRE group (-1.70 kg; 95% CI, -2.56 to -0.83; P < .001). There was also a significant difference in appendicular lean mass index between groups (-0.16 kg/m2; 95% CI, -0.27 to -0.05; P = .005). There were no significant changes in any of the other secondary outcomes within or between groups. There were no differences in estimated energy intake between groups.
Conclusions and Relevance: Time-restricted eating, in the absence of other interventions, is not more effective in weight loss than eating throughout the day.
Trial Registration: ClinicalTrials.gov Identifiers: NCT03393195 and NCT03637855.
I feel it would perhaps have been better to try to eat only from 06.00 to 14.00 than from 12.00 to 20.00
This is a useful study as there is a growing perception that intermittent fasting is very effective in weight loss
Time restricted eating is another new fad diet, based on physiological studies. This study looks at one outcome, weight loss, and finds no advantage to this practice. There could be other benefits of time-restricted eating; evidence is lacking.
Small but well done study.
This is an interesting study that says nothing - too short of a follow-up to draw any conclusions, a sample size that is too small and that is heavily biased (less than 15% of the primary sample), with a substantial drop out in the study (20+%). Thus, it adds little, if any to our knowledge today.
Randomized trials are experimental demonstrations of the efficacy of time-restricted eating intervention. Although the results did not favor the intervention, these findings can prevent practitioners from adopting ineffective clinical management.