Influence of Intermittent Fasting on Body Composition, Physical Performance, and the Orexinergic System in Postmenopausal Women: A Pilot Study

<b>Objective</b>: This study aims to evaluate the effects of different nutritional strategies, specifically intermittent fasting (IF) combined with high-intensity interval training (HIIT) versus a low-calorie diet (LCD), on body composition, physical performance, and the orexinergic system in postmenopausal women. <b>Methods</b>: A randomized controlled trial involving thirty postmenopausal women (mean age 57.50 ± 6.50 years) was conducted over eight weeks, comparing the two dietary approaches alongside an 8-week HIIT program. Body composition was assessed using bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA). Performance metrics included handgrip strength and the 6-min walking test (6MWT). Salivary samples were analyzed for Orexin-A (OX-A) levels pre- and post-intervention. <b>Results</b>: Significant improvements in health metrics, such as heart rate (HR) and endurance, were found, with mean HR changes showing a significant difference (F = 5.943, <i>p</i> = 0.033) between the groups at T1. Orexin-A levels reflected significant metabolic regulation shifts in relation to other variables, showing a change from baseline to post-intervention values at T1 (F = 10,931, <i>p</i> = 0.033). Flexibility (sit and reach) significantly improved by 6% (<i>p</i> < 0.05), as well as VO2 max (10%, <i>p</i> < 0.05), both highlighted as key predictors of overall health outcomes. Additionally, Cohen's d analyses indicated that the dietary groups exhibited notable differences in endurance, with the LCD group showing a Cohen's d of -0.90, suggesting a large effect size compared with the control group. <b>Conclusions</b>: The combination of IF and HIIT is an effective nutritional strategy for enhancing body composition and physical performance in postmenopausal women, potentially mediated by changes in the orexinergic system. Further research is warranted to explore long-term effects and underlying mechanisms.