What this Trial Is About

Early-onset metabolic disturbances (such as mild hyperglycemia, subclinical dyslipidemia, excess body fat, and reduced functional capacity) represent one of the major public health challenges among middle-aged and older adults. Although body mass index (BMI) remains the primary clinical criterion for classifying excess weight, growing evidence indicates that BMI does not adequately discriminate cardiometabolic risk, particularly in individuals classified as overweight who present elevated body fat levels (Wu et al., 2024). Several studies have identified altered metabolic phenotypes that do not meet the criteria for obesity, including the so-called "metabolically unhealthy normal weight" (MUNW) or "metabolically unhealthy non-obese" phenotypes. These individuals are characterized by excess body fat, central adiposity, and alterations in glucose and lipid metabolism despite having a non-obese BMI (Stefan, 2020). This profile is associated with increased insulin resistance, low-grade systemic inflammation, and elevated cardiovascular risk, underscoring the need for targeted interventions in "metabolically challenged" individuals. Xiong et al. (2024) demonstrated that metabolic health status independently predicts cardiovascular risk, even when BMI is within non-obese ranges. This evidence supports the rationale of the present project: to intervene in a group of adults without clinical obesity (BMI \< 30 kg/m²) but presenting at least two indicators of mild metabolic dysfunction. Nutritional supplements with thermogenic properties that promote fat oxidation and satiety-such as phenylcapsaicin, an analog of capsaicin designed to improve bioavailability and reduce pungency, thereby enhancing tolerability in adults-may offer a promising complementary strategy. Recent studies have shown that low doses of phenylcapsaicin were sufficient to increase fat oxidation during exercise, reduce respiratory exchange ratio, and lower maximal heart rate during submaximal testing compared with placebo (Jiménez-Martínez et al., 2023a). Furthermore, additional research reported that phenylcapsaicin improved strength performance, reduced perceived exertion, and attenuated markers of muscle damage following resistance training (Jiménez-Martínez et al., 2023b). These findings suggest that thermogenic and fat-oxidation-enhancing supplementation may act as a safe and effective metabolic modulator, particularly when combined with exercise, positioning it as an innovative strategy for adults presenting mild metabolic risk. The present study would integrate: (1) a multicomponent functional exercise program designed to improve strength, balance, and aerobic capacity in older adults; (2) a thermogenic and fat-oxidation-enhancing nutritional supplement as a safe metabolic activation strategy; (3) a standardized dietary control protocol to isolate the specific effects of the supplementation; (4) dual-energy X-ray absorptiometry (DXA) for precise body composition assessment; (5) hormonal and lipid biomarkers to evaluate underlying physiological mechanisms; and (6) validated questionnaires addressing quality of life, sleep, and appetite to capture the holistic dimension of this stage of adulthood. This multidimensional approach would provide an innovative intervention for a growing yet underexplored population: non-obese but metabolically challenged adults at increasing cardiometabolic risk. References: * Jiménez-Martínez P, Sánchez-Valdepeñas J, Cornejo-Daza PJ, Cano-Castillo C, Asín-Izquierdo I, Alix-Fages C, Pareja-Blanco F, Colado JC. Effects of different phenylcapsaicin doses on neuromuscular activity and mechanical performance in trained male subjects: a randomized, triple-blinded, crossover, placebo-controlled trial. Front Physiol. 2023a Aug 2; 14: 1215644. * Jiménez-Martínez P, Cornejo-Daza PJ, Sánchez-Valdepeñas J, Asín-Izquierdo I, Cano-Castillo C, Alix-Fages C, Pareja-Blanco F, Colado JC. Effects of different phenylcapsaicin doses on resistance training performance, muscle damage, protein breakdown, metabolic response, ratings of perceived exertion, and recovery: a randomized, triple-blinded, placebo-controlled, crossover trial. J Int Soc Sports Nutr. 2023b Dec; 20 (1): 2204083. * Stefan N. Metabolically healthy and unhealthy normal weight and obesity. Endocrinol Metab (Seoul). 2020 Sep;35(3):487-493. * Xiong Q, Zang Y, Li J, An Y, and Yu S. Comparison of cardiovascular disease risk association with metabolic unhealthy obesity identified by body fat percentage and body mass index: Results from the 1999-2020 National Health and Nutrition Examination Survey. PLoS One. 2024 Aug 14; 19 (8): e0305592. * Wu Y, Li D, and Vermund SH. Advantages and limitations of the body mass index (BMI) to assess adult obesity. Int J Environ Res Public Health. 2024 Jun 10; 21 (6): 757.

Effects of Physical Exercise and a Nutritional Supplement on Body Composition, Metabolic Function, and Overall Health in Adults With a Metabolically Challenging Profile