Association of Body Composition with Insulin Resistance in a Middle-Aged Population

This study aims to clarify the relationship between body mass index, body composition indices, and the risk of insulin resistance. From November 2019 to January 2020, 573 employees aged 40-60 years from Anhui Hong Sifang Co., Ltd, underwent physical and biochemical assessments. We analyzed fasting glucose, serum insulin, and homeostasis model assessment of insulin resistance differences across body mass index and body composition, and examined associations with insulin resistance risk. Among 573 participants (mean age 48.3 years, 67.4% men), 20.8% had insulin resistance. Overweight/obesity, central obesity, high visceral adipose index, high fat mass%, limb/trunk fat%, and elevated fat-muscle-ratio were significantly associated with higher fasting serum insulin, homeostasis model assessment of insulin resistance, and insulin resistance prevalence (all p<0.05). The increase in these factors corresponded with increased insulin resistance risk, with odds ratios and 95% confidence intervals of 4.71 (2.88-7.72), 5.80 (3.60-9.35), 4.88 (3.07-7.74), 4.25 (2.71-6.69), 3.48 (2.19-5.52), 5.72 (3.45-9.47), and 4.41 (2.73-7.13). Conversely, lower muscle mass%, limb/trunk muscle%, bone mineral content%, total body water%, extracellular water%, and intracellular water% were linked to higher fasting serum insulin and homeostasis model assessment of insulin resistance, indicating a protective effect against insulin resistance with odds ratios and 95% confidence intervals of 4.34 (2.67-7.08), 3.53 (2.21-5.62), 3.49 (2.20-5.53), 5.35 (3.24-8.85), 4.73 (2.91-7.70), 4.99 (3.06-8.16), and 4.98 (3.04-8.14). The findings suggest a significant association between body composition indices and insulin resistance risk. Increased fat mass raises the risk of insulin resistance, while higher muscle mass, bone mineral content, and body water content have a protective effect. Additionally, the balance between fat and muscle influences insulin resistance levels.