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 (VO2 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 < 0001) 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 (F = 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. (C) 2009 Elsevier B.V. All rights reserved.