Background: Despite established relationships between physical activity (PA) or physical fitness (fitness) and metabolic risk, the prospective association is not well understood. The purpose of this study was to determine whether metabolic risk in young adults is associated with 20-year PA or fitness trajectories. Methods: Young adults were from the Coronary Artery Risk Development in Young Adults (CARDIA) study, baseline ages 18-30 years (n=4161). PA was determined from a self-reported questionnaire administered at baseline and at follow-up exams at years 2, 5, 7, 10, 15, and 20. Fitness (seconds) was estimated from a graded exercise treadmill test at baseline and years 7 and 20. Baseline metabolic risk was calculated using age-adjusted principal components analysis (elevated=top 10% of first factor), for each sex-race group, from mean arterial pressure, glucose, waist circumference, triglycerides, and high-density lipoprotein cholesterol. Repeated measures general linear modeling estimated PA and fitness trajectories over 20 years, separately in sex-race groups, adjusting for age and smoking status. Results: PA was significantly lower among those with elevated metabolic risk compared with normal risk at baseline and each subsequent time point (black and white men, white women; all P<0.0001; black women P=0.27). Significant and consistent results were also found with fitness trajectories for all sex-race groups (P<0.0001). Despite these lower PA and fitness levels at baseline in young adults with elevated metabolic compared with normal risk, 20-year trajectories declined at similar rates. Conclusion: Elevated metabolic risk is associated with lower levels of PA and fitness in early adulthood, and these differences persist over 20 years. © Copyright 2013, Mary Ann Liebert, Inc.