Fat loss and muscle gain: The possible role of striatal dopaminergic tone in determining the efficacy of physical exercise.

The effectiveness of exercise for obesity is contentious due to individual response variability. Owing to the roles of dopamine in motor functions, metabolism, and appetite, this study aimed to identify striatal dopamine as a predictor of variability in exercise response, specifically in terms of fat loss and muscle gain. Healthy non-exercising males completed an 8-week program, exercising 1 h, 4 days a week. Striatal dopaminergic tone was assessed by measuring dopamine transporter availability using technetium-99 m labelled tropane derivative, [99mTc]TRODAT-1 (TRODAT), single-photon emission computed tomography, and body composition (fat and muscles mass) was analysed using bioelectrical impedance. Lower baseline dopamine levels were associated with greater fat mass loss (r = 0.58, p = 0.006), percentage fat mass loss (r = 0.53, p = 0.013), and increase in muscle mass (ß = -0.53, p = 0.035, after taking age and smoking status as covariates). These findings enhance our understanding of obesity neurobiology and exercise response variability, necessitating further research for targeted interventions based on dopaminergic profiles.

Fat loss and muscle gain: The possible role of cortical glutamate in determining the efficacy of physical exercise.

BACKGROUND: Physical exercise is widely acknowledged for its health benefits, but its effectiveness in treating obesity remains contentious due to variability in response. Owing to the roles of glutamate in appetite regulation, food addiction, and impulsivity, this observational cohort-study evaluated medial prefrontal cortex (mPFC) glutamate as a predictor of variability in exercise response, specifically in terms of fat loss and muscle gain. METHODS: Healthy non-exercising adult men (n = 21) underwent an 8-week supervised exercise program. Baseline glutamate levels in the mPFC were measured through magnetic resonance spectroscopy. For exercise-dependent changes in body composition (fat and muscle mass), basal metabolic rate (BMR), and blood metabolic biomarkers related to lipid and glucose metabolism, measurements were obtained through bioelectrical impedance and blood sample analyses, respectively. RESULTS: The exercise program resulted in significant improvements in body composition, including reductions in percentage body fat mass, body fat mass, and waist-to-hip ratio and an increase in mean muscle mass. Furthermore, BMR and metabolic indicators linked to glucose and lipids exhibited significant changes. Notably, lower baseline glutamate levels were associated with greater loss in percentage body fat mass (r = 0.482, p = 0.027), body fat mass (r = 0.441, p = 0.045), and increase in muscle mass (r = -0.409, p = 0.066, marginal) following the exercise program. CONCLUSION: These preliminary findings contribute to our understanding of the neurobiology of obesity and emphasize the significance of glutamate in regulating body composition. The results also highlight cortical glutamate as a potential predictor of exercise-induced fat loss and muscle gain.