Abstract
Background: Obesity is associated with functional limitations in muscle performance. Current evidence demonstrating the effect of obesity on muscle quality is limited. The true effect of obesity upon skeletal muscle mass, including any interactions with ageing effects, remains to be elucidated. The present study investigates the impact of obesity on the stimulation of muscle growth.
Methods: A data set of 44 severely obese men and 64 women were analysed. All subjects had a BMI ≥29.7 kg/m². Body weight (Wt), body height (Ht), hand circumference (HdC) and the circumference of the waist (WC) were measured and processed by the Dahlmann-Body Analysis (DBA) system. The result is the amount of skeletal muscle mass (SMM, kg). Association between weight variables and BMI were analysed by linear regression analysis. The slope of the regression line was tested to be significant by t-test. The goodness of fit is assessed by coefficient of determination (R²) and the standard error of the estimate (SEE). Significance of determination coefficient between variables are tested by F-test. Muscle mass data are compared with DXA derived equations estimating the appendicular lean soft tissue (ALST). Mean values of these findings are tested by ANOVA
Results: Age ranged between 18 and 72 years. All subjects had a BMI ≥ 29.7 (kg/m²). The mean values of ΔSMM as an estimate of muscle mass increase calculated by the DBA-system were 11.8 ±3.6 kg for men and 8.9 ±2.6 kg for women, respectively, demonstrating a linear, significantly rising relationship to BMI (ß > 0, p<0.001) and a low variance between both parameters. The comparison of DBA calculated muscle mass data with DXA derived equations estimating ALST revealed satisfactory results. Relation between age and the increase of muscle mass adjusted for height (ΔSMMI, kg/m²) was not significantly different from zero.
Conclusion: The DBA model is obviously reliable to predict SMM. Based on these data, the study revealed for the first time that obesity stimulates muscle growth in a linear manner. A decrease of muscle mass over age could not be demonstrated for our study population. The current study provides another step on the roadmap to develop the DBA model as a tool in public health in relation to management of obesity and sarcopenia.