Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population : A Randomized Controlled Trial

Abstract

Background: Time-restricted eating (TRE), without calorie counting, has become a popular weight loss strategy, yet long-term randomized trials evaluating its efficacy are limited.

Objective: To determine whether TRE is more effective for weight control and cardiometabolic risk reduction compared with calorie restriction (CR) or control.

Design: 12-month randomized controlled trial. (ClinicalTrials.gov: NCT04692532).

Setting: University of Illinois Chicago from January 2021 to September 2022.

Participants: 90 adults with obesity.

Intervention: 8-hour TRE (eating between noon and 8:00 p.m. only, without calorie counting), CR (25% energy restriction daily), or control (eating over a period of 10 or more hours per day). Participants were not blinded.

Measurements: Change in body weight, metabolic markers, and energy intake by month 12.

Results: Seventy-seven persons completed the study. Mean age was 40 years (SD, 11), 33% were Black, and 46% were Hispanic. Mean reduction in energy intake was -425 kcal/d (SD, 531) for TRE and -405 kcal/d (SD, 712) for CR. Compared with the control group, weight loss by month 12 was -4.61 kg (95% CI, -7.37 to -1.85 kg; P ≤ 0.01) (-4.87% [CI, -7.61% to -2.13%]) for the TRE group and -5.42 kg (CI, -9.13 to -1.71 kg; P ≤ 0.01) (-5.30% [CI, -9.06% to -1.54%]) for the CR group, with no statistically significant difference between TRE and CR (0.81 kg [CI, -3.07 to 4.69 kg; P = 0.68]) (0.43% [CI, -3.48% to 4.34%]).

Limitation: Not blinded, not powered to detect relatively large differences in weight loss, and lack of adjustment for multiple comparisons.

Conclusion: Time-restricted eating is more effective in producing weight loss when compared with control but not more effective than CR in a racially diverse population.

Primary funding source: National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases.

Figure 1.. Participant flow diagram.

CR = calorie restriction; TRE = time-restricted eating.

Figure 2.. Change in body weight and energy intake between groups over 12 months.

CR = calorie restriction; TRE = time-restricted eating. Top. Body weight: Data were included for 90 participants; means were estimated using an intention-to-treat analysis using a linear mixed model. Error bars indicate 95% CIs for each parameter from baseline by diet group. Middle. Box plot of change in absolute weight from baseline to month 12 by treatment group. Participants with missing values for weight at month 12 are excluded from the figure. Bottom. Energy intake: Data are expressed as mean (SD); only observed values included. A total of 19 of 30 TRE participants returned all food records; 17 of 30 CR participants returned all food records. The widths of the CIs have not been adjusted for multiplicity and should therefore not be used to reject or not reject treatment effects.