Relationships between thermic effect of food, insulin resistance and autonomic nervous activity

Background: The thermic effect of food (TEF) is higher in lean than in obese human subjects. Objective: Relationships between TEF and insulin resistance during meals, from the point of view of autonomic nervous activity, were evaluated. Methods : Autonomic nervous activity was evaluated in 20 young adults using the spectral analysis of heart rate variability from one hour before to two hours after a meal. Heart rate data were analyzed based on low frequency components (LF power, 0.04 - 0.15Hz),high frequency components (HF power, 0.15-0.40 Hz), and LF/HF ratios. Energy expenditure and the TEF were measured 30 min after a meal. Homeostasis model of insulin resistance index (HOMA-IR) was also measured. Results : The LF/HF ratio was significantly increased 30minafter a meal (p<0.05).No correlation between LF power and HF power with TEF was found, but the LF/HF ratio was significantly and positively correlated with TEF(r＝＋0.56,p<0.05). Moreover, a significant negative correlation was found between the HOMA-IR and TEF (r＝－0.601, p<0.05). Conclusions : The findings suggest that a reduction in insulin sensitivity induces a poor response of sympathetic nervous activity in the postprandial phase and a reduction in postprandial energy expenditure.