Body Composition, Obesity, and Cardiorespiratory Fitness in the Community

Purpose: Cardiorespiratory fitness (CRF) is an integrative measure of physiologic health, but how CRF relates to different body composition components and cardiometabolic health in community-dwelling adults remains uncertain, especially in obesity. Methods: In Framingham Heart Study (FHS) Generation 3/Omni-2 participants, body composition measures from dual-energy X-ray absorptiometry (DXA) were related to peak oxygen uptake (VO 2 ) and complementary exercise phenotypes assessed via cardiopulmonary exercise testing in sex-stratified multivariable linear models. Secondary analyses examined correlates of peak VO 2 when indexed to total body weight or lean mass. Results: Among 2647 participants (53% women, mean age 54 years, body mass index [BMI] 27.8 kg/m 2 ), lean mass was the strongest correlate of CRF among body composition measures (FDR <5%) and, along with age and height, accounted for 44-48% of the variance in peak VO 2 . A 1 kg-higher lean mass was associated with a 43 ml/min-higher absolute peak VO 2 . While there was broad consistency across age, sex-based differences in the relations of body composition and CRF were observed, with women demonstrating stronger positive associations between CRF and fat mass compared to men. Peak VO 2 displayed distinct cardiometabolic correlates depending on whether it was indexed to total body weight versus lean mass: “metabolically healthy” obesity displayed lower peak VO 2 compared to “metabolically healthy” non-obesity with indexing to total body weight, but peak VO 2 was similar between these two categories with indexing to lean mass. Conclusions: Lean mass is the strongest correlate of CRF in middle-aged, community-dwelling individuals. Indexing peak VO 2 to lean versus total mass results in different conclusions regarding the intersections of CRF with obesity and metabolic health and emphasizes the role of cardiometabolic risk factors beyond obesity itself.