<p>Obesity poses a significant public health challenge among middle-aged women, driven by physiological changes associated with aging and menopause. This parallel-group, assessor-blinded, four-arm randomized controlled trial investigated the effects of 12-week 8-hour flexible time-restricted eating (flexTRE) and aerobic exercise (EX), alone or in combination (flexTRE+EX), on body composition and metabolic health in a free-living setting. Participant enrolment began on September 1^st 2023 and data collection was completed on July 1^st 2024. Conducted at a single research site in Hong Kong, the trial enrolled women aged 40–60 years with overweight/obesity. Participants were randomized in a 1:1:1:1 ratio to a flexTRE, EX, flexTRE+EX, or control (CON) group (n = 26 per group), with all 104 participants included in the final intention-to-treat analysis. Outcomes were assessed at baseline, and week 12. The primary outcome was fat mass. The flexTRE+EX group achieved the greatest fat mass reduction compared to the CON group (adjusted mean difference [99% Confidence Interval] −2.85 kg [−4.01 to −1.69]), and additional benefit over the flexTRE group alone (−1.56 kg [−2.74 to −0.38]), and the EX group alone (−2.01 kg [−3.21 to −0.81]). Secondary outcomes were reported in the main text. No serious adverse events were reported, and adherence was high (83%-87%) across intervention groups. These findings suggest that the combined approach effectively reduces fat mass and enhances related metabolic parameters, providing a feasible and effective strategy in middle-aged women facing overweight/obesity. Trial registration: ChiCTR2300074846.</p>