Protein restricted, high carbohydrate diets improve metabolic health in rodents, yet the precise dietary components that are responsible for these effects have not been identified. Further, the applicability of these studies to humans is unclear. Here, we demonstrate in a randomized controlled trial that a moderately protein restricted (PR) diet also improves markers of metabolic health in humans. Intriguingly, we find that feeding mice a diet specifically reduced in branched chain amino acids (BCAAs) is sufficient to improve glucose tolerance and body composition equivalently to a PR diet, via metabolically distinct pathways. Our results highlight a critical role for dietary quality at the level of amino acids in the maintenance of metabolic health, and suggest that diets specifically reduced in BCAAs, or pharmacological interventions in this pathway, may offer a translatable way to achieve many of the metabolic benefits of a PR diet.

Weight loss is the cornerstone of therapy for people with obesity because it can ameliorate or completely resolve the metabolic risk factors for diabetes, coronary artery disease, and obesity-associated cancers. The potential health benefits of diet-induced weight loss are thought to be compromised by the weight-loss-associated loss of lean body mass, which could increase the risk of sarcopenia (low muscle mass and impaired muscle function). The objective of this review is to provide an overview of what is known about weight-loss-induced muscle loss and its implications for overall physical function (e.g., ability to lift items, walk, and climb stairs). The currently available data in the literature show the following: ) compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality;) diet-induced weight loss reduces muscle mass without adversely affecting muscle strength; ) weight loss improves global physical function, most likely because of reduced fat mass;) high protein intake helps preserve lean body and muscle mass during weight loss but does not improve muscle strength and could have adverse effects on metabolic function; ) both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength. We therefore conclude that weight-loss therapy, including a hypocaloric diet with adequate (but not excessive) protein intake and increased physical activity (particularly resistance-type exercise), should be promoted to maintain muscle mass and improve muscle strength and physical function in persons with obesity.

According to the Mini Nutritional Assessment (MNA), a high prevalence of malnutrition was found out in both genders: 26% of F and 16.3% of M were classified as being malnourished (MNA<17); 40.9% of F and 35% of M were at risk of malnutrition (MNA 17-23,5). The prevalence of malnutrition was significantly higher in NH subjects in both sexes. Moreover, a relationship was shown between malnutrition and inability to shop, prepare and cook meals because of a low income, distance from markets or supermarkets as well as impossibility to drive the car or to use public transportation. This study confirms the necessity to routinely perform nutritional status evaluation in elderly subjects, to carry out training courses for health workers (doctors, nurses, psychologists, dietitians), to implement nutritional education of the geriatric population, to develop tools and guidelines for health workers and caregivers, to identify and reduce clinical, functional, social or economic risk factors for malnutrition.

Calorie Restriction (CR) without malnutrition slows aging and increases average and maximal lifespan in simple model organisms and rodents. In rhesus monkeys long-term CR reduces the incidence of type 2 diabetes, cardiovascular disease and cancer, and protects against age-associated sarcopenia and neurodegeneration. However, so far CR significantly increased average lifespan only in the Wisconsin, but not in the NIA monkey study. Differences in diet composition and study design between the 2 on-going trials may explain the discrepancies in survival and disease. Nevertheless, many of the metabolic and hormonal adaptations that are typical of the long-lived CR rodents did not occur in either the NIA or WNPRC CR monkeys. Whether or not CR will extend lifespan in humans is not yet known, but accumulating data indicate that moderate CR with adequate nutrition has a powerful protective effect against obesity, type 2 diabetes, inflammation, hypertension, cardiovascular disease and reduces metabolic risk factors associated with cancer. Moreover, CR in human beings improves markers of cardiovascular aging, and rejuvenates the skeletal muscle transcriptional profile. More studies are needed to understand the interactions between CR, diet composition, exercise, and other environmental and psychological factors on metabolic and molecular pathways that regulate health and longevity.