Cardiorespiratory Fitness, BMI, Mortality, and Cardiovascular Disease in Adults with Overweight/Obesity and Type 2 Diabetes

INTRODUCTION: We estimated the effects of cardiorespiratory fitness (CRF) and body mass index (BMI) at baseline on mortality and cardiovascular disease events in people with type 2 diabetes who participated in the Look AHEAD randomized clinical trial. METHODS: Look AHEAD compared effects of an intensive lifestyle intervention with diabetes support and education on cardiovascular disease events in 5145 adults age 45-76 yr with overweight/obesity and type 2 diabetes. In 4773 participants, we performed a secondary analysis of the association of baseline CRF during maximal treadmill test (expressed as metabolic equivalents (METs)) on mortality and cardiovascular disease events during a mean follow-up of 9.2 yr. RESULTS: The mean (SD) CRF was 7.2 (2.0) METs. Adjusted for age, sex, race/ethnicity, BMI, intervention group, and β-blocker use, all-cause mortality rate was 30% lower per SD greater METs (hazard ratio (HR) = 0.70 (95% confidence interval, 0.60 to 0.81); rate difference (RD), -2.71 deaths/1000 person-years (95% confidence interval, -3.79 to -1.63)). Similarly, an SD greater METs predicted lower cardiovascular disease mortality (HR, 0.45; RD, -1.65 cases/1000 person-years) and a composite cardiovascular outcome (HR, 0.72; RD, -6.38). Effects of METs were homogeneous on the HR scale for most baseline variables and outcomes but heterogeneous for many on the RD scale, with greater RD in subgroups at greater risk of the outcomes. For example, all-cause mortality was lower by 7.6 deaths/1000 person-years per SD greater METs in those with a history of cardiovascular disease at baseline but lower by only 1.6 in those without such history. BMI adjusted for CRF had little or no effect on these outcomes. CONCLUSIONS: Greater CRF is associated with reduced risks of mortality and cardiovascular disease events.