Author(s): WONG, S., DAI, Z., Institution: THE CHINESE UNIVERSITY OF HONG KONG, Country: CHINA, Abstract-ID: 849

INTRODUCTION:
Time-restricted eating (TRE) has emerged as a popular dietary strategy among athletes and active individuals aiming to optimize body composition without strict calorie counting. While TRE effectively reduces fat mass, concerns persist regarding its impact on fueling sufficiency and the preservation of lean mass. Specifically, compressing the eating window may inadvertently induce Low Energy Availability or suboptimal protein distribution, compromising muscle protein synthesis and recovery. This systematic review and meta-analysis quantitatively assessed the effects of ad-libitum TRE on daily energy and protein intake to determine its viability and risks for active populations.
METHODS:
A systematic literature search was conducted across five databases (including PubMed, Scopus, and SPORTDiscus) for randomized controlled trials. Eligible studies compared ad-libitum TRE against control diets in adults and reported quantitative data on daily energy (kcal) and protein (g) intake. Data synthesis utilized a random-effects model to calculate pooled mean differences (MD) and 95% confidence intervals (CI). Meta-regression analyses explored heterogeneity based on eating-window duration and age. Methodological quality was assessed using the Cochrane Risk of Bias tool (RoB 2), and certainty of evidence was evaluated via Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach .
RESULTS:
Twenty-four RCTs (n = 1,602; mean age 44 years) were included. Ad-libitum TRE resulted in a significant spontaneous reduction in daily energy intake compared to controls (MD: −254.8 kcal/day; 95% CI [−307.1 to −202.4]; P < 0.001). Concurrently, significant reductions were observed in daily protein intake (MD -6.1 g/d; 95% CI [-10.3, -1.8]; P=0.009; I2=58.6%; 95% PI [-18.8, 6.7]). Meta-regression revealed a linear dose-response relationship: every 1-hour reduction in the eating window was associated with a further decrease of 48.5 kcal/day in energy and 3.2 g/day in protein intake. Furthermore, age significantly moderated protein intake, with younger participants exhibiting greater spontaneous reductions (β = 0.45 g/day per year of age).
CONCLUSION:
Ad-libitum TRE is a potent strategy for inducing a spontaneous energy deficit, making it effective for athletes prioritizing fat loss or weight-category management. However, the concurrent reduction in protein intake may pose a risk for muscle protein synthesis and recovery, particularly when utilizing shorter eating windows or in younger adults. These findings imply that the application of TRE in performance contexts may require strategic dietary oversight. Considerations for periodization and compensatory protein feeding could be beneficial to mitigate potential risks of low energy availability and support lean mass preservation during restricted feeding windows.