Time-restricted diet is not more beneficial than calorie restriction alone
Calorie Restriction with or without Time-Restricted Eating in Weight Loss
Introduction and methods
Since many diets are difficult to adhere to and only lead to modest, short-term weight loss, better diet options are eagerly awaited. Time-restricted eating has become more popular because it is thought to be easy to follow strategy. Although time-restricted eating showed a reduction in body weight and fat mass in patients with obesity in several (small) clinical studies [1-5], long-term efficacy and safety are still uncertain.
Aim of the study
The authors investigated the effects of time-restricted eating with calorie restriction on weight loss and metabolic risk factors in obese patients compared with daily calorie restriction alone.
In this single-center observer-blind RCT , 139 patients were randomly assigned to 8-hour time-restricted eating (n = 69) or daily calorie restriction (n = 70) for 12 months. Required calorie intake was identical for both regimens: 1200–1500 kcal/day for women and 1500–1800 kcal/day for men. The eating period for the time-restricted–eating group (from 8:00 a.m. to 4:00 p.m.) was chosen because many Chinese people eat their biggest meal in the middle of the day rather than in the evening.
Participants were recruited from the general public in Guangzhou, China. Inclusion criteria were age 18–75 years and BMI 28–45 kg/m2. Exclusion criteria were, among others, diabetes mellitus, serious cardiovascular or cerebrovascular disease within 6 months before randomization, active participation in another weight-loss program, and use of medications affecting weight or energy balance. All participants received dietary counseling by trained health coaches.
The primary outcome was the difference in change in body weight from baseline to 12 months between the two groups. Secondary outcomes included differences in changes in BMI, waist circumference, body fat, body lean mass, and metabolic risk factors (including plasma glucose levels, insulin sensitivity, serum lipid levels, and blood pressure) between groups.
- Mean change in body weight from baseline to 12 months was −8.0 kg (95% CI: −9.6 to −6.4) in the time-restriction group and −6.3 kg (95% CI: −7.8 to −4.7) in the daily-calorie-restriction group (mean net difference: −1.8 kg; 95% CI: −4.0 to 0.4 ).
- Percentages of participants with a weight loss of >5%, >10%, or >15% at 12 months were similar in the two groups.
- Subgroup analyses for sex, BMI at baseline, insulin sensitivity, and diet adherence also showed similar weight changes for the two diet regimens.
- Mean net difference in BMI from baseline to 12 months was −0.7 kg/m2 (95% CI: −1.5 to 0.1 ).
- Mean net difference in waist circumference from baseline to 12 months was −1.8 cm (95% CI: −4.0 to 0.5).
- Mean net difference in body fat mass from baseline to 12 months was −1.5 kg (95% CI: −3.1 to 0.2).
- Mean net difference in body lean mass from baseline to 12 months was −0.3 (95% CI: −1.1 to 0.5).
- After 12 months, there were also no significant net differences in reduction of body fat percentage, abdominal visceral and subcutaneous fat, or liver fat, nor significant net differences in changes in glucose levels (fasting and 2-hour postprandial), insulin sensitivity and resistance, lipid levels, or systolic and diastolic blood pressure.
After one year, time-restricted eating was not more beneficial in reducing body weight, body and visceral fat, or metabolic risk factors in Chinese patients with obesity than daily calorie restriction. This indicates that caloric intake restriction explained most of the favorable effects seen with this specific time-restricted–eating regimen, not the eating period.