ABSTRACT
High-protein diets have been shown to be beneficial for cardiometabolic health; however, the specific effects of dietary protein are often confounded by parallel changes in energy or carbohydrate intakes. In general, energy-restricted diets with higher protein and reduced carbohydrates produce a greater loss of body weight and body fat while minimizing the loss of lean tissues and lead to improvements in glycemic regulations and dyslipidemia. Specific roles of protein in cardiometabolic health may be most evident by focusing on amino acid metabolism in skeletal muscle. Research studies in areas of obesity and weight loss, aging and sarcopenia, and exercise physiology have cast new light on dietary protein needs and challenged the existing dietary guidelines as inadequate for long-term muscle health. These studies have identified a meal-based protein requirement, in large part, associated with the unique roles of the essential amino acid leucine in the regulation of skeletal muscle protein synthesis and energy metabolism. Postmeal increases in intracellular leucine concentrations initiate a signaling cascade that triggers muscle protein synthesis and increases fatty acid oxidation. These changes in muscle metabolism appear to explain the metabolic advantages of dietary protein including protecting calorie-burning muscle tissue, increasing energy expenditure characterized as diet-induced thermogenesis, and partitioning of weight loss to body fat. This review will evaluate the meal-based protein-centric needs for skeletal muscle metabolism and their relationship to cardiometabolic health.
