Article - The Effect of Time-Restricted Eating Combined with Exercise on Body Composition and Metabolic Health: A Systematic Review and Meta-Analysis.

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Take home message

Combining time restricted eating with exercise may be beneficial for managing body weight, fat mass and metabolic health. Further research is needed to confirm these results in specific populations, exercise types and time frames.

Evidence category

A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)

Summary review

Introduction

The aim of this study was to investigate the efficacy of a combination of time restricted eating (TRE) and exercise for improving body composition and metabolic health in adults.

Methods

19 randomised controlled trials (RCT) with a total population of N=568 adults aged 18-62 years were included in this review.
11 RCTs were in males, 6 in females and 2 were mixed sex. The number of participants ranged from 12 to 131 and intervention durations from 4 weeks to 12 months.
8 RCTs had unrestricted energy intake (ad libitum) while in 11 RCTs, energy intake was restricted (non-ad libitum). All RCTs used control groups following a normal dietary pattern. All groups included exercise.
Outcome measures included: body mass, fat mass, free fat mass, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density cholesterol (HDL-C), triglycerides (TG), fasting glucose, inflammatory markers, cytokines and adipokines (insulin-like growth factor 1 (IGF-1), IL-6, TNF-A, leptin and adiponectin).
Subgroups included: Ad-libitum and non-ad-libitum energy intake within a TRE window, and intervention durations of >4 (moderate-term) or < 4 weeks (short-term).

Results

A reduction in body mass (p<0.01) and fat mass (p<0.01) was found in TRE plus exercise groups. Analysis of subgroups found this may only apply for non-ad libitum diet groups (p<0.01) with moderate-term study durations (p<0.01). There was no difference in fat-free mass with intervention duration (p=0.23).
There was no difference between TRE with exercise and control on fasting glucose and insulin (p=0.35), though reductions in fasting glucose were reported in subgroups for non-ad libitum TRE with exercise intervention groups (p0.01) with durations of >4 weeks (p=0.04) only.
There was no difference in lipid profile between groups (p>0.05), though subgroup analysis found reductions in TG in non-ad libitum diet groups (p<0.01) with study durations >4 weeks (p<0.01) only, a reduction in LDL-C for non-ad libitum diet groups (p<0.01) with moderate durations (p<0.01).
The study also revealed reductions in leptin (p<0.01) but no difference in adiponectin (P=0.11) with the combined strategy of TRE plus exercise.
Reductions in IGF-1 (p<0.01), IL-6 (p=0.01), TNF-A (p<0.01) were also observed.

Conclusion

This study found that combining TRE with exercise was effective for reducing fat mass and body weight as well as improving lipid profiles and specific metabolic markers in adults. However, further research is needed to confirm these results in specific populations, exercise types and durations.

Clinical practice applications

TRE and exercise may be an effective strategy for reducing body and fat mass and improving metabolic health in adults but likely only with an energy restricted diet for more than 4 weeks
Fat mass loss may be due to increased fat oxidation stimulated by exercise and the use of fat as a fuel source, however, further research into mechanisms is needed.
Participant characteristics and metabolic health varied between studies; 11 studies were in physically active males, 5 studies were in overweight or obese females, 1 study in normal weight, active females and 2 studies were mixed sex, 1 of which was in obese individuals, 88% of which were females.
Exercise types and duration of fasting varied between studies.

Considerations for future research

Heterogeneity in participant characteristics, metabolic profiles, exercise types, duration of fasting and timing of meals and control diet types may have influenced the results.
Further research is needed to confirm these results in specific populations, exercise types and time periods.

Abstract

BACKGROUND

Time-restricted eating (TRE) is increasingly popular, but its benefits in combination with exercise still need to be determined.

OBJECTIVES

This systematic review and meta-analysis aimed to evaluate the efficacy of TRE combined with exercise compared with control diet with exercise in improving the body composition and metabolic health of adults.

METHODS

Five electronic databases were searched for relevant studies. Randomized controlled trials (RCTs) examining the effect of TRE combined with exercise on body composition and metabolic health in adults were included. All results in the meta-analysis are reported as mean difference (MD) with 95% confidence interval (CI). Study quality was assessed using the revised Cochrane Risk of Bias Tool and Grading of Recommendations Assessment, Development, and Evaluation assessment.

RESULTS

In total, 19 RCTs comprising 568 participants were included in this systematic review and meta-analysis. TRE combined with exercise likely reduced the participants' body mass (MD: -1.86 kg; 95% CI: -2.75, -0.97 kg) and fat mass (MD: -1.52 kg; 95% CI: -2.07, -0.97 kg) when compared with the control diet with exercise. In terms of metabolic health, the TRE combined with exercise group likely reduced triglycerides (MD: -13.38 mg/dL, 95% CI: -21.22, -5.54 mg/dL) and may result in a reduction in low-density lipoprotein (MD: -8.52 mg/dL; 95% CI: -11.72, -5.33 mg/dL) and a large reduction in leptin (MD: -0.67 ng/mL; 95% CI: -1.02, -0.33 ng/mL). However, TRE plus exercise exhibited no additional benefit on the glucose profile, including fasting glucose and insulin, and other lipid profiles, including total cholesterol and high-density lipoprotein concentrations, compared with the control group.

CONCLUSIONS

Combining TRE with exercise may be more effective in reducing body weight and fat mass and improving lipid profile than control diet with exercise. Implementing this approach may benefit individuals aiming to achieve weight loss and enhance their metabolic well-being. This study was registered in PROSPERO as CRD42022353834.