Optimised Skeletal Muscle Mass as a Key Strategy for Obesity Management

Our internationally accepted criterion for diagnosing obesity, prioritizing its management options, and assessing treatment outcomes, is based on an anachronistic ratio, the ‘Body Mass Index’ (BMI). On an individual level, BMI has potential to mislead, can provide an inaccurate indication of cardiometabolic risk, places too much emphasis on a reduction of overall body weight, and contributes towards misunderstanding of the quiddity of obesity, and a more dispassionate societal perspective and response. In this review, we resurrect the skeletal muscle (SM) as a tissue hidden in plain sight in the context of obesity. We provide an overview of the role that SM plays in influencing metabolic health and efficiency. We discuss the complex interlinks between the SM and the Adipose Tissue (AT) through key myokines and adipokines, and argue that rather than two separate tissues, the SM and AT should be considered as a single entity: the ‘Adipo-Muscle Axis’. We discuss the vicious circle of sarcopenic obesity, in which age- and obesity-related decline in SM mass contributes to worsened metabolic status and insulin resistance, that in turn further compounds SM mass and function. We provide an overview of the approaches that can mitigate against the decline of SM mass in the context of negative energy balance, including the optimisation of dietary protein intake and resistance physical exercises, and of novel molecules in development that target the SM, that will play an important role in the future management of obesity. Finally, we argue that the Adipo-Muscle Ratio (AMR) would provide a more clinically meaningful descriptor and definition of obesity than BMI, and would help to shift our focus regarding its effective management away from merely inducing weight loss, but rather towards optimising the AMR with proper attention to the maintenance and augmentation of SM mass and function.