Background: The longitudinal association between obesity, weight variability, and health status outcomes is important for patients with coronary disease and diabetes. Methods: The BARI 2D was a multicenter randomized clinical trial designed to evaluate treatment strategies for patients with both documented stable ischemic heart disease and type 2 diabetes. We examined BARI 2D participants for 4 years to study how body mass index (BMI) was associated with health status outcomes. Health status was evaluated by the Duke Activity Status Index (DASI), RAND Energy/fatigue, Health Distress, and Self-rated Health. Body mass index was measured quarterly throughout follow-up years, and health status was assessed at each annual follow-up visit. Variation in BMI measures was separated into between-person and within-person change in longitudinal analysis. Results: Higher mean BMI during follow-up years (the between-person BMI) was associated with poorer health status outcomes. Decreasing BMI (the within-person BMI change) was associated with better Self-rated health. The relationships between BMI variability and DASI or Energy appeared to be curvilinear and differed by baseline obesity status. Decreasing BMI was associated with better outcomes if patients were obese at baseline but was associated with poorer DASI and Energy outcomes if patients were nonobese at baseline. Conclusions: For patients with stable ischemic heart disease and diabetes, weight gain was associated with poorer health status outcomes, independent of obesity-related comorbidities. Weight reduction is associated with better functional capacity and perceived energy for obese patients but not for nonobese patients at baseline. © 2011 Mosby, Inc.