Higher fasting serum insulin is associated with increased resting energy expenditure in nondiabetic schizophrenia patients.

BACKGROUND: Insulin has emerged as an important determinant of food intake, energy expenditure, and weight control. This study examined the relationship between fasting serum insulin level and resting energy expenditure (REE) in a cross-sectional sample of nondiabetic schizophrenia patients.
METHODS: Subjects were recruited from an urban community mental health clinic. Each subject underwent a series of anthropometric measures and an indirect calorimetry measure. A fasting blood sample was taken for plasma glucose, serum insulin, and lipid profile.
RESULTS: Seventy-one subjects (54 male, 17 female) were included in the study. There was a significant positive relationship between REE and fasting serum insulin level (r = .39, p = .001). Stepwise multiple regression analysis was performed with various characteristics such as age, race, antipsychotic agent used, fat-free mass, BMI, waist circumference, waist-hip ratio, physical activity level, and fasting serum insulin as candidate predictors for REE. Only fat-free mass and insulin were able to enter into the regression model, which indicates that higher fat-free mass and higher fasting serum insulin level predict increased REE.
CONCLUSIONS: A higher fasting serum insulin level is associated with an increased REE, which may prevent further weight gain in nondiabetic patients with schizophrenia.