AbstractBackgroundSedentary lifestyles and poor physical fitness are major contributors to the current obesity and cardiovascular disease pandemic.HypothesisDaily physical activity and cardiorespiratory fitness are correlated in morbidly obese individuals in their free‐living environment.MethodsTen morbidly obese participants continuously wore an activity sensor that measured caloric expenditure, minute‐by‐minute physical activity, and steps/day over a 72‐h period. Following collection of the device data, structured cardiorespiratory fitness testing was performed on each subject.ResultsMean caloric expenditure for all individuals was 2,668 ± 481 kcal/d. On average, subjects took 3,763 ± 2,223 steps. On average 23 h and 51.6 min per d were spent sleeping or engaged in sedentary activity (<3 metabolic equivalents [METs]) and the remaining 8.4 min were spent in moderate activity (3–6 METs). Average peak VO2 was 16.8 ± 4.7 mL/kg/min. Higher peak VO2 correlated with higher total caloric expenditure (TCE; r = 0.628, p = 0.05) and trended with higher steps/day (r = 0.591, p = 0.07).ConclusionsMost morbidly obese participants in this study were markedly sedentary. These study results may provide important links between obesity, poor fitness, and cardiovascular disease. Copyright © 2009 Wiley Periodicals, Inc.