Effects of obesity, physical activity, and cardiorespiratory fitness on blood pressure, inflammation, and insulin resistance in the National Health and Nutrition Survey 1999-2002

Background and aims: This study was designed to elucidate the effects of obesity, self-reported physical activity and cardiorespiratory fitness on blood pressure, inflammation, and insulin resistance. Methods and results: Data from 950 Caucasian subjects ranging in age from 19 to 49 years from the National Health and Nutrition Survey (NHANES), 1999-2002, were included to construct a population-based observational study. Cardiorespiratory fitness (VO 2 max) was predicted from a submaximal exercise stress test. Self-reported physical activity was measured by metabolic equivalent score transformed from a questionnaire. A structural equation model (SEM) was developed to examine the relationship between obesity, cardiorespiratory fitness, self-reported physical activity, and hypertension, inflammation, and insulin resistance. The model showed that obesity was positively linked to hypertension (B=0.50, P<0.001) and C-reactive protein (CRP; B=0.15, p<0.05), which in turn led to insulin resistance (B=0.44, P<0.05). Increased cardiorespiratory fitness was negatively associated with CRP (Γ=-0.23, P<0.01), but not correlated to hypertension after adjustment for potential confounding factors. No significant association was found between self-reported physical activity and hypertension, insulin resistance, and CRP. Conclusion: Obesity contributes to the development of hypertension, inflammation, and insulin resistance. Improved cardiorespiratory fitness might lead to clinical and biochemical improvement in insulin resistance by reducing the inflammatory state. © 2009 Elsevier B.V.