Metabolically obese normal weight (Wt) occurs in people who have high prevalence of cardiovascular disease even with normal body mass index (BMI). In this study, we determined the relationship between low muscle mass and metabolic syndrome which is known to be associated with cardiovascular disease in aged people with normal BMI.

This study used the data of Korea National Health and Nutrition Examination Survey. Aged people (≥ 65 years) with normal BMI (18.5 to 22.9 kg/m²) were enrolled. Low muscle mass class I was defined as appendicular skeletal muscle divided by Wt 1 to 2 standard deviation below the mean of gender specific young healthy adult and class II was defined as below 2 standard deviations.

The prevalence of low muscle mass class I and II were 18.8% and 5.2% in men and 11.2% and 2.2% in women, respectively. In men and women, low muscle mass and metabolic syndrome was associated with each other after adjusting for age. After further adjusting for BMI, smoking status, alcohol consumption, and exercise frequency, the relationship was maintained in aged men. Moreover in aged men, the risk of metabolic syndrome was increased according to the grade increase in low muscle mass class.

In the aged with normal BMI, low muscle mass was a risk factor of metabolic syndrome. Furthermore, in normal BMI men, when the degree of low muscle mass was enhanced, the risk of metabolic syndrome was increased.