Cardiorespiratory fitness and vigorous leisure-time physical activity modify the association of small size at birth with the metabolic syndrome.

OBJECTIVE Small size at birth has been associated with components of the metabolic syndrome, but little is known about the association with the metabolic syndrome itself or whether leisure-time physical activity (LTPA) and cardiorespiratory fitness modify that association. We studied the association of size at birth with the metabolic syndrome. RESEARCH DESIGN AND METHODS Birth weight and length, the metabolic syndrome (World Health Organization criteria), LTPA over the previous 12 months, and VO(2max) were assessed in 462 nondiabetic middle-aged Finnish men who were part of a population-based cohort study. RESULTS Men with a ponderal index (kg/m(3)) at birth in the lower third had higher fasting insulin and glucose levels than men in the upper third in age-adjusted analyses and were at least twofold more likely to have the metabolic syndrome, even in men without cardiovascular disease. Adjustment for childhood or adult socioeconomic status or adult BMI did not attenuate the association. Thinness at birth was even more clearly associated with hyperinsulinemia and the metabolic syndrome in men engaging in <25 min/wk of vigorous LTPA and in men with a VO(2max) <28.6 ml x kg(-1) x min(-1) or <2.44 l/min. In active and fit men, however, the association was absent. CONCLUSIONS Small size at birth was associated with the metabolic syndrome in middle-aged men already before development of diabetes or cardiovascular disease. Thinness at birth may carry with it lifelong metabolic consequences, but regular strenuous physical activity and maintenance of cardiorespiratory fitness may alleviate or eliminate those consequences.