No evidence for metabolic adaptation during exercise-related energy compensation

The constrained energy model posits that the increased total daily energy expenditure (TDEE) in response to exercise is often less than the energy cost of the exercise prescribed. The mechanisms behind this phenomenon, coined "exercise-related energy compensation" (ExEC), are poorly understood, and it is unknown if ExEC is coupled with metabolic adaptation. Using a randomized controlled 24-week exercise intervention, individuals who demonstrated ExEC were identified. Changes to all components of TDEE and metabolic adaptation were assessed using doubly labeled water over 14 days and room calorimetry over 24-h 48% of individuals exhibited ExEC (-308 ± 158 kcals/day). There were no statistically significant differences in sex, age, or BMI between ExEC and non-ExEC. ExEC was associated with baseline TDEE (r = -0.50, p = 0.006). There were no statistically significant differences in metabolic adaptations for 24 h, sleep, or resting expenditures. These findings reveal that ExEC occurs independent of metabolic adaptation in sedentary components of EE.