Skeletal Muscle Ratio: A Complete Mediator of Physical Activity and HbA1C in Type 2 Diabetes

An increase in the physical activity level reduces body weight, decreases body fat, increases skeletal muscle mass, and improves serum glucose; however, the influence of body composition parameters on the relationship between physical activity and serum glucose remains unclear.

This study investigated whether skeletal muscle and visceral fat affect the relationship between high physical activity and long-term serum glucose goals.

This cross-sectional study recruited patients with type 2 diabetes. The Chinese version of the International Physical Activity Questionnaire was used for estimating the physical activity level, and a bioimpedance device was used to measure the skeletal muscle ratio (skeletal muscle mass/total body weight, %) and visceral fat area (cm²). Hierarchical logistic regression models and mediation tests were conducted according to Hayes' procedures.

Of the total 543 Chinese individuals with type 2 diabetes enrolled, HbA1C levels of fewer than half (n = 243, 44.8%) met the target of ≤7.0%. The skeletal muscle ratio was found to be a complete mediator (OR = 0.920, 95% CI: 0.848 to 0.998; indirect effect: -0.238, 95% CI: -0.525 to -0.020) of the relationship between high physical activity and the target HbA1C level after controlling for visceral fat area (indirect effect: -0.013, 95% CI: -0.183 to 0.156), age, time since diabetes diagnosis, and rice intake.

Nurses should include an increase in the skeletal muscle ratio as an objective in physical activity interventions for patients with type 2 diabetes to help them achieve their long-term serum glucose goals.