Many people often refer to a ‘bad metabolism’ as an important parameter explaining weight management issues. Relative potency of metabolic pathways largely dictates the fate of food consumed by an individual. Metabolic assessments produce personalized data on important aspects of energy and nutrient handling. Indeed, small but detectable differences in the basic metabolic rate (BMR) may account for the differences in physical activity or caloric restriction that individuals would need to implement to successfully manage their weight. Accordingly, differences in BMR are useful for the design of nutritional interventions and exercise regiments and their relative caloric impact. Hormonal analysis and responses to exercise sessions may further elucidate metabolic features and provide complementary information for designing personalized nutritional and exercise strategies. Research on genetic, proteomic and metabolomic aspects is expected to provide new tools for clinical assessments in the future.