2 weeks ago
#repost @dr.eddiejo with @get_repost
What is the interaction among a caloric deficit, resistance training, dietary protein, and muscle protein metabolism? Firstly, an energy deficit promotes a general shift in fuel utilization in that there is an increased reliance on endogenous (stored) fuels such as fat, carbohydrate/glycogen, and amino acids from proteins within various organs in the body including muscle. Thus, during an energy deficit there is a general increase in muscle protein degradation, in turn providing a free amino acid pool to help meet the body's energy needs through their oxidation or serve as a substrate for glucose production (to help maintain blood glucose homeostasis). Also, a lower portion of the free amino acid pool would be reincorporated back into muscle proteins since protein synthesis (or any anabolic process) is energy consuming (not favorable during an energy deficit). Overtime, muscle mass may decrease since the intracellular protein content eventually diminishes. Because an energy deficit exerts these effects on muscle protein metabolism, it is common to experience a loss of lean mass during a caloric deficit diet which at times may reduce the quality of weight loss and exacerbate the normal suppression of resting metabolic rate that accompanies weight loss. The traditional thought is that there is nothing we can do about this. However, an expanding body of recent evidence adequately counters this contention. High volume resistance training together with a higher protein intake (2-3x U.S RDA) has shown to facilitate lean mass retention or growth during a caloric deficit. My recent study showed this was possible even with an extreme ~1000 kcal/day deficit in obese subjects! It appears that increasing dietary protein intake during a caloric deficit provides a greater free amino acid pool to support energy and glucose needs, alleviate the reliance on muscle protein breakdown, and afford the building blocks to synthesize muscle proteins. All one needs now is a stressor to the muscle to stimulate protein synthesis. Here enters resistance training.