Physical activity energy expenditure predicts progression toward the metabolic syndrome independently of aerobic fitness in middle-aged healthy Caucasians: the Medical Research Council Ely Study.

OBJECTIVE To examine over a period of 5.6 years the prospective associations between physical activity energy expenditure (PAEE), aerobic fitness (Vo(2max)), obesity, and the progression toward the metabolic syndrome in a population-based cohort of middle-aged men and women (n = 605) who were free of the metabolic syndrome at baseline. RESEARCH DESIGN AND METHODS PAEE was measured objectively by individually calibrated heart rate against energy expenditure. Vo(2max) was predicted from a submaximal exercise stress test. Fat mass and fat-free mass were assessed by bio-impedance. A metabolic syndrome score was computed by summing the standardized values for obesity, hypertension, hyperglycemia, insulin resistance, hypertriglyceridemia, and the inverse level of HDL cholesterol and expressed as a continuously distributed outcome. Generalized linear models were used to examine the independent prospective associations between PAEE and Vo(2max) and the metabolic syndrome score after adjusting for sex, baseline age, smoking, socioeconomic status, follow-up time, and baseline phenotypes. RESULTS PAEE predicted progression toward the metabolic syndrome, independent of baseline metabolic syndrome, body fat, Vo(2max), and other confounding factors (standardized beta = -0.00085, P = 0.046). This association was stronger when excluding the adiposity component from the metabolic syndrome (standardized beta = -0.0011, P = 0.035). Vo(2max) was not an independent predictor of the metabolic syndrome after adjusting for physical activity (standardized beta = 0.00011, P = 0.93). CONCLUSIONS PAEE predicts progression toward the metabolic syndrome independent of aerobic fitness, obesity, and other confounding factors. This finding underscores the importance of physical activity for metabolic disease prevention even when an improvement in aerobic fitness is absent.