Early, Late, & Self-Selected Time-Restricted Eating: Impact on Hepatic Fat, Liver Health, & Fecal Microbiota in Adults with Overweight or Obesity

Background and aimsThe optimal eating window for time-restricted eating (TRE) remains unclear. We investigated the effects of 8-hour TRE combined with usual care (UC, a Mediterranean diet-based education program), versus UC alone over 12 weeks on hepatic fat fraction, liver health markers, and fecal microbiota in adults with overweight or obesity. MethodsIn this multicenter randomized trial, participants (50% women) were assigned to UC (n=49), early TRE (n=49), late TRE (n=52), or self-selected TRE (n=47). Hepatic fat fraction was assessed by MRI; liver markers included elastography-based parameters, liver enzymes, and circulating biomarkers. Fecal microbiota was analyzed by 16S rRNA gene sequencing. ResultsHepatic fat fraction decreased significantly within the three TRE groups (all P[&le;]0.02), but no between-group differences were observed when comparing early TRE (mean difference [MD]: -0.4%; P=0.95), late TRE (MD: -1.5%; P=0.15), and self-selected TRE groups (MD: -0.7%; P=0.77) with the UC group, or among the TRE groups themselves (all P[&ge;]0.41). Similarly, no between-group differences were found in liver health markers and fecal microbiota. Participants with metabolic dysfunction-associated steatotic liver disease at baseline as well as those achieving [&ge;]5% weight loss had greater reductions in hepatic fat fraction than those who did not (MD: -2.7 and -2.6%; respectively, both P<0.001). A higher proportion of participants in the TRE groups achieved [&ge;]5% weight loss compared with UC (41-44% vs 16%; P=0.001). ConclusionThese findings suggest that the timing of the eating window in TRE may not impact liver fat or microbiota composition beyond the effects of weight loss, though the study was not powered for secondary outcomes. The study was registered on ClinicalTrials.gov (identifier: NCT05310721)