Resistance exercise protects mice from protein-induced metabolic dysfunction

Abstract

AbstractLower intake of dietary protein is associated with improved metabolic health and reduced rates of age-associated diseases in humans, while low protein (LP) diets improve fitness and extend the lifespan of diverse animal species. Paradoxically, many athletes and bodybuilders consume high protein (HP) diets and protein or branched-chain amino acid supplements, yet remain fit and metabolically healthy. Here, we examine the effect of weight pulling, a validated progressive resistance exercise training regimen in mice fed either a LP diet or an isocaloric HP diet. We find that sedentary HP-fed male C57BL/6J mice gain significantly more fat mass than sedentary mice fed a LP diet, despite not consuming more calories. Resistance exercise was protective against this effect, blocking excess fat gain overall and in specific fat depots in HP-fed mice, but did not alter fat mass gain or distribution in LP-fed mice. In accordance with the widespread belief that high protein diets help promote muscle mass gain, the HP diet augmented the hypertrophy of the soleus, flexor digitorum longus (FDL) and the forearm flexor complex that occurred in response to exercise. While strength increased more rapidly in HP-fed mice, the maximum strength pulled by LP and HP-fed mice after 12 weeks was indistinguishable. Our results confirm the widespread belief that HP diets can augment muscle hypertrophy and strength gain induced by resistance exercise without negative metabolic consequences, while demonstrating that LP diets may be relatively advantageous in the sedentary. The results here highlight the need to consider both dietary composition and activity levels, not simply calories, when taking a precision nutrition approach to health.