Author(s): AZCÁRATE, U., ALFARO-MAGALLANES, V.M., BERMEJO MARTÍNEZ, G., GARCÍA-ARIVE, J., OSES, M., ECHARTE, J., IZQUIERDO, C., AZPIROZ-ALCOZ, H., MEDRANO, M., LABAYEN, I., Institution: PUBLIC UNIVERSITY OF NAVARRA - ES-Q3150012G, Country: SPAIN, Abstract-ID: 1645

INTRODUCTION:
Menopause-related alterations in energy metabolism are linked to changes in substrate utilization, including a reduced capacity to oxidize fat at rest1. Calorie-restricted (CR) weight loss interventions may influence lipid metabolism through changes in energy balance and body composition2. Time-restricted eating (TRE) has emerged as an alternative to CR for weight loss; however, whether resting fat oxidation is altered during short-term weight loss, particularly when combined with resistance training (RT), remains unclear. Therefore, this study examined the effects of a 12-week TRE intervention, TRE combined with RT (TRE+RT), and CR combined with RT (CR+RT) on resting fat oxidation in postmenopausal women with overweight or obesity.
METHODS:
In a 12-week randomized controlled trial (NCT05912309; DOI: 10.1016/j.numecd.2024.103844), sixty-nine postmenopausal women (58.8±3.9 years; 81.2±14.3 kg; 45.6±3.5% body fat) with overweight or obesity were assigned to TRE, TRE+RT, or CR+RT. Participants in the TRE groups reduced their daily eating window to 8 hours (self-selected but maintained on a fixed schedule), whereas the CR+RT group followed an individualized hypocaloric diet (−500 kcal·day⁻¹ relative to total energy expenditure estimated from indirect calorimetry). RT groups completed supervised, machine-based resistance training sessions three times per week (90-min; 8–12 repetitions, with progressive loads at 65–80% of one-repetition maximum). Resting fat oxidation (g·min⁻¹) was assessed via indirect calorimetry in the fasted state at baseline (PRE) and post-intervention (POST). Data were analyzed using linear mixed-effects models with time, group, and time-by-group as fixed effects. Models were adjusted for changes in body and lean mass as covariates. Results are reported as estimated marginal means with 95% confidence intervals.
RESULTS:
No significant between-group differences were observed in resting fat oxidation changes following the 12-week intervention when adjusting for change in body mass (time × group p=0.169). Resting fat oxidation did not significantly change within any group from PRE to POST: TRE (0.0833±0.0037 vs. 0.0796±0.0040 g·min⁻¹; p=0.337), TRE+RT (0.0803±0.0036 vs. 0.0828±0.0039 g·min⁻¹; p=0.512), or CR+RT (0.0789±0.0038 vs. 0.0847±0.0039 g·min⁻¹; p=0.127). Estimated marginal means were comparable across groups at PRE and POST. Results were similar when adjusting for change in lean mass (time × group p=0.179).
CONCLUSION:
In postmenopausal women with overweight or obesity, resting fat oxidation is preserved after a 12-week weight loss intervention induced by TRE or CR, with or without RT. These findings suggest that lifestyle-induced weight loss strategies may not be associated with an impairment in resting lipid oxidation, regardless of concomitant changes in body mass or lean mass.
1. Kleis-Olsen et al. Acta Physiol. 2024.
2. Liu et al. N Engl J Med. 2022.