Interaction between time-restricted eating and high-intensity interval training on cardiometabolic outcomes in women with overweight or obesity: a 2 × 2 factorial randomised controlled trial

Abstract Time-restricted eating (TRE) and high-intensity interval training (HIIT) are promising strategies for improving cardiometabolic health in women with overweight or obesity, but whether they interact synergistically remains unclear. We evaluated their independent and combined effects on cardiometabolic outcomes. This prespecified secondary analysis of a 2 × 2 factorial randomised controlled trial assigned 131 women with overweight or obesity (median BMI 30·7 kg/m 2 ; age 18–45 years) to TRE, HIIT, TRE + HIIT or control for 7 weeks. TRE limited daily intake to a ≤10-hour eating window; HIIT comprised three supervised treadmill sessions weekly. The primary analysis followed the intention-to-treat principle after multiple imputation; linear mixed-effects models estimated TRE and HIIT main effects and their interaction, with Holm–Bonferroni-adjusted interaction p -values; per-protocol sensitivity analyses excluded dropouts. No significant TRE × HIIT interaction was detected. In intention-to-treat main-effect analyses, TRE reduced body weight (–3·36 kg, p = 0·008), fat mass (–1·53 kg, p = 0·025) and visceral fat area (–12·82 cm 2 , p < 0·001), but also reduced muscle mass (–0·80 kg, p = 0·020) and modestly lowered HDL-C. HIIT main effects were minimal in the intention-to-treat analysis, while per-protocol sensitivity analyses suggested reductions in BMI, fat mass, total cholesterol, LDL-C and HbA1c, although these findings are more susceptible to attrition bias. Within the constraints of limited power and short duration, no interaction between TRE and HIIT was detected. TRE-related adiposity benefits should therefore be weighed against concurrent reductions in muscle mass and changes in lipid profiles. Larger, adequately powered, longer-term trials are needed to confirm these findings and clarify their clinical relevance. Trial registration: NCT04019860.