Changes in Cardiorespiratory Fitness and Percent Body Fat with Incident Metabolic Syndrome

Abstract

The associations of changes in cardiorespiratory fitness (fitness) and % body fat (fatness) with metabolic syndrome (MS) are unclear. PURPOSE: We examined independent and combined associations of changes in fitness and fatness with incident MS in 5,575 adults (14% women) aged 18-82 years at baseline who were examined ≥3 times during 1979-2006. METHODS: All participants were free of CVD, cancer, abnormal ECG, diabetes, and MS; and all achieved ≥85% of age-predicted maximal heart rate on the treadmill test at baseline and 2nd examination. Fitness levels, in metabolic equivalents (METs), were estimated from a maximal treadmill test. Fatness was determined by underwater weighing or 7-site skinfold measurements. Changes in fitness and fatness were calculated as the changes in maximal METs or % body fat per year between baseline and 2nd examination (mean 2.1 years), and categorized into 'loss', 'stable', and 'gain'. Cox regression model included sex, age, examination year, maximal METs, % body fat, systolic blood pressure, glucose, triglyceride, HDL-cholesterol, waist circumference, smoking status, alcohol intake, physical activity at baseline, parental diabetes, and changes in % body fat (for fitness change) or maximal MET (for fatness change). RESULTS: There were 924 incident MS during 6.3 years of follow-up (from the 2nd through the last examination). The relative risks (RR) and 95% confidence intervals (CI) for incident MS were 0.72 (0.60-0.86) for stable fitness, and 0.67 (0.56-0.81) for fitness gain compared with fitness loss, and 1.14 (0.94-1.38) for stable fatness, and 1.30 (1.11-1.53) for fatness gain compared with fatness loss after adjusting for confounders and changes in fatness or fitness. In the joint analysis, compared with fitness loss and fatness gain group, participants with stable fitness or fitness gain showed lower risk of MS regardless of fatness change patterns, and the lowest risk was observed in fitness gain and fatness loss group (RR 0.45, 95% CI 0.35-0.58). CONCLUSIONS: Both fitness and fatness are independent risk factors of incident MS. Maintaining or improving fitness is associated with lower risk of MS, while increasing fatness is associated with higher risk of MS. Supported by NIH Grant AG06945, HL62508, DK088195, and an unrestricted research grant from the Coca-Cola Company.