Differential effects of rapid or slow body weight loss on muscle weight and protein degradation pathways in rat skeletal muscle

Abstract

Background Many athletes restrict energy intake to achieve a certain body mass category, aesthetic benefits or to attain a better force-to-mass ratio to improve performance. This rapid weight loss, also known as “weight cutting”, usually involves several-day fasting until a target weight is achieved. However, fasting is a well-known stimulus to activate two major protein degradation pathways, the autophagy-lysosome and ubiquitin-proteasome systems, resulting in skeletal muscle atrophy. An alternative dietary weight loss approach commonly practiced by athletes is daily caloric restriction, which consists of decreasing energy intake by 10-30% every day, resulting in slower body weight loss compared with fasting. The caloric restriction-induced slower body weight loss has also been shown to induce skeletal muscle atrophy. Since no study has directly compared the effects of rapid vs. slow body weight loss on muscle weight and the major protein degradation pathways during an equivalent body weight loss, it still remains unclear which rapid or slow weight loss approach is effective in maintaining skeletal muscle mass. The purpose of this study was thus to assess the effects of rapid or slow body weight loss on muscle weight and the protein degradation pathways in skeletal muscle.