Is time-restricted eating (8/16) beneficial for body weight and metabolism of obese and overweight adults? A systematic review and meta-analysis of randomized controlled trials

Time-restricted eating affects human adipose tissue fat mobilization

OBJECTIVE

Time-restricted eating (TRE), a dietary approach that confines food intake to specific time windows, has shown metabolic benefits. However, its impact on body weight loss remains inconclusive. The objective of this study was to investigate the influence of early TRE (eTRE) and delayed TRE (dTRE) on fat mobilization using human adipose tissue (AT) cultures.

METHODS

Subcutaneous AT was collected from 21 participants with severe obesity. We assessed fat mobilization by measuring glycerol release in AT culture across four treatment conditions: control, eTRE, dTRE, and 24-h fasting.

RESULTS

TRE had a significant impact on lipolysis (glycerol release [mean (SD)] in micromoles per hour per gram: control, 0.05 [0.003]; eTRE, 0.10 [0.006]; dTRE, 0.08 [0.005]; and fasting, 0.17 [0.008]; p < 0.0001). Both eTRE and dTRE increased lipolysis compared with the control group, with eTRE showing higher glycerol mobilization than dTRE during the overall 24-h time window, especially at the nighttime/habitual sleep episode (p < 0.0001). Further analysis of TRE based on fasting duration revealed that, independently of the time window, glycerol release increased with fasting duration (in micromoles per hour per gram: 8 h = 0.08 [0.001]; 12 h = 0.09 [0.008]; and 16 h of fasting = 0.12 [0.011]; p < 0.0001).

CONCLUSIONS

This study provides insights into the potential benefits of TRE on fat mobilization and may guide the design of future dietary strategies for weight management and metabolic health.

Effect of Isocaloric, Time-Restricted Eating on Body Weight in Adults With Obesity : A Randomized Controlled Trial

BACKGROUND

Time-restricted eating (TRE) lowers body weight in many studies. Whether TRE induces weight loss independent of reductions in calorie intake, as seen in rodent studies, is unknown.

OBJECTIVE

To determine the effect of TRE versus a usual eating pattern (UEP) on body weight in the setting of stable caloric intake.

DESIGN

Randomized, isocaloric feeding study. (ClinicalTrials.gov: NCT03527368).

SETTING

Clinical research unit.

PARTICIPANTS

Adults with obesity and prediabetes or diet-controlled diabetes.

INTERVENTION

Participants were randomly assigned 1:1 to TRE (10-hour eating window, 80% of calories before 1 p.m.) or UEP (≤16-hour window, ≥50% of calories after 5 p.m.) for 12 weeks. Both groups had the same nutrient content and were isocaloric with total calories determined at baseline.

MEASUREMENTS

Primary outcome was change in body weight at 12 weeks. Secondary outcomes were fasting glucose, homeostatic model assessment for insulin resistance (HOMA-IR), glucose area under the curve by oral glucose tolerance test, and glycated albumin. We used linear mixed models to evaluate the effect of interventions on outcomes.

RESULTS

All 41 randomly assigned participants (mean age, 59 years; 93% women; 93% Black race; mean BMI, 36 kg/m2) completed the intervention. Baseline weight was 95.6 kg (95% CI, 89.6 to 101.6 kg) in the TRE group and 103.7 kg (CI, 95.3 to 112.0 kg) in the UEP group. At 12 weeks, weight decreased by 2.3 kg (CI, 1.0 to 3.5 kg) in the TRE group and by 2.6 kg (CI, 1.5 to 3.7 kg) in the UEP group (average difference TRE vs. UEP, 0.3 kg [CI, -1.2 to 1.9 kg]). Change in glycemic measures did not differ between groups.

LIMITATION

Small, single-site study; baseline differences in weight by group.

CONCLUSION

In the setting of isocaloric eating, TRE did not decrease weight or improve glucose homeostasis relative to a UEP, suggesting that any effects of TRE on weight in prior studies may be due to reductions in caloric intake.

PRIMARY FUNDING SOURCE

American Heart Association.

Time-Restricted Feeding Attenuates Metabolic Dysfunction-Associated Steatohepatitis and Hepatocellular Carcinoma in Obese Male Mice

Metabolic dysfunction-associated steatotic liver disease (MASLD) has surpassed the hepatitis B virus and hepatitis C virus as the leading cause of chronic liver disease in most parts of the Western world. MASLD (formerly known as NAFLD) encompasses both simple steatosis and more aggressive metabolic dysfunction-associated steatohepatitis (MASH), which is accompanied by inflammation, fibrosis, and cirrhosis, and ultimately can lead to hepatocellular carcinoma (HCC). There are currently very few approved therapies for MASH. Weight loss strategies such as caloric restriction can ameliorate the harmful metabolic effect of MASH and inhibit HCC; however, it is difficult to implement and maintain in daily life, especially in individuals diagnosed with HCC. In this study, we tested a time-restricted feeding (TRF) nutritional intervention in mouse models of MASH and HCC. We show that TRF abrogated metabolic dysregulation induced by a Western diet without any calorie restriction or weight loss. TRF improved insulin sensitivity and reduced hyperinsulinemia, liver steatosis, inflammation, and fibrosis. Importantly, TRF inhibited liver tumors in two mouse models of obesity-driven HCC. Our data suggest that TRF is likely to be effective in abrogating MASH and HCC and warrant further studies of time-restricted eating in humans with MASH who are at higher risk of developing HCC.

Effectiveness of Time-Restricted Eating with Caloric Restriction vs. Caloric Restriction for Weight Loss and Health: Meta-Analysis

Time-restricted eating (TRE) is an increasingly popular dietary strategy for weight loss. Recent studies suggest that combining TRE with caloric restriction (CR) may have more favorable effects on both physical and biochemical aspects when compared with CR alone. Therefore, we performed a meta-analysis to compare the effects of TRE with CR vs. CR alone on anthropometric and biochemical measures in overweight or obese adults. We reviewed articles from PubMed, Web of science, EMBASE, and the Cochrane Library published before 25 May 2023. The meta-analysis incorporated data from seven randomized controlled trials of nine interventions, with a total of 231 participants in the TRE with CR group and 227 participants in the CR-only group. Data were analyzed using RewMan version 5.4.1. All results in our meta-analysis were described as mean difference (MD) with 95% confidence interval (Cl). Results showed that TRE with CR compared to CR alone resulted in significantly greater reductions in body weight (MD: -2.11 kg, 95% CI: -2.68 kg to -1.54 kg, p = < 0.00001, I2 = 42%), body fat mass (MD: -0.75 kg, 95% CI: -1.35 kg to -0.16 kg, p = 0.01; I2 = 0%), and waist circumference (MD: -1.27 cm, 95% CI: -2.36 cm to -0.19 cm, p = 0.02, I2 = 0%), while no additional impact of TRE in combination with CR in comparison to CR on serum biochemical parameters were found. Our results suggest that the improvement in biochemical parameters are mainly caused by CR, while improvements in anthropometric parameters are further enhanced by TRE.