Very-low-carbohydrate diets and preservation of muscle mass

Background I would like to compliment Noakes et al. on their wellcontrolled study comparing effects of different diets on body composition and cardiovascular risk [1]. The authors suggested that a very-low-carbohydrate diet (VLCARB) may not be associated with protein-sparing, because their dual-energy X-ray absorptiometry (DEXA) data indicated that both VLCARB and very-low-fat diet resulted in significantly more loss of lean mass than the high-unsaturated fat diet. It should be noted, however, that DEXA provides a measure of lean soft tissue (LST), and the original notion that LST hydration is constant is not correct. Rather, LST hydration varies as a function of extraand intracellular water distribution [16]. I feel it is very unlikely that the VLCARB group catabolized more muscle protein than the high-unsatured fat diet group. This commentary provides some basic information on metabolic adaptations that lead to sparing of muscle protein during a VLCARB, and reviews studies examining the effects of VLCARB interventions on body composition.