ARS | Publication request: Approaches for quantifying energy intake and % calorie restriction (CR) during CR interventions in humans: the multicenter CALERIE study

Submitted to: American Journal of Physiology - Endocrinology and Metabolism
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 2011
Publication Date: February 15, 2012
Citation: Racette, S., Das, S., Bhapkar, M., Hadley, E., Roberts, S.B., Ravussin, E., Pieper, C., Delany, J., Kraus, W., Rochon, J., Redman, L. 2012. Approaches for quantifying energy intake and % calorie restriction (CR) during CR interventions in humans: the multicenter CALERIE study. American Journal of Physiology - Endocrinology and Metabolism. 302(4):E441-448.

Interpretive Summary: Calorie restriction (CR) is a component of most weight-loss interventions and a potential strategy to slow aging. Accurate determination of energy intake and %CR is critical when interpreting the results of CR interventions; this is best achieved using the doubly labeled water method to quantify total energy expenditure (TEE). The costs and analytical requirements of this method, however, preclude its repeated use in many clinical trials. Our primary aim was to determine which TEE assessment time points are critical for quantifying average energy intake and % CR during CR interventions. Adults randomized to a CR intervention in the multicenter CALERIE study underwent measures of TEE by doubly labeled water and body composition at baseline and months 1, 3, and 6. Average % CR achieved during the intervention was 25.5 +/-8.7%, computed using a reference approach that included four TEE assessment time points. TEE declined 11.0 +/- 9.7% within 1 month of beginning CR and then stabilized. In summary, optimal quantification of energy intake and % CR during weight loss necessitates either an early TEE measure to capture the rapid reduction in TEE during CR or appropriate weighting of the baseline and final TEE values to accurately reflect metabolic adaptations that accompany weight loss.

Technical Abstract: Calorie restriction (CR) is a component of most weight-loss interventions and a potential strategy to slow aging. Accurate determination of energy intake and %CR is critical when interpreting the results of CR interventions; this is best achieved using the doubly labeled water method to quantify total energy expenditure (TEE). The costs and analytical requirements of this method, however, preclude its repeated use in many clinical trials. Our primary aim was to determine which TEE assessment time points are critical for quantifying average energy intake and %CR during CR interventions. Adults randomized to a CR intervention in the multicenter CALERIE study underwent measures of TEE by doubly labeled water and body composition at baseline and months 1, 3, and 6. Average %CR achieved during the intervention was 25.5+/-8.7%, computed using a reference approach that included four TEE assessment time points (i.e., TEEbaseline, month 1, month 3, month 6) plus 6-month change in body composition. Approaches that included fewer TEE assessments yielded %CR values of 23.7+/-9.0% (TEEbaseline, month 3, month 6), 25.7+/-8.6% (TEEbaseline, month 1, month 6), 20.9+/-7.1% (TEEbaseline, month 6; weighted equally), 24.5+/-9.1% (TEEbaseline, month 6; weighted 1/6, 5/6), and 15.5+/-5.8% (TEEbaseline). TEE declined 11.0+/-9.7% within 1 month of beginning CR and then stabilized. In summary, optimal quantification of energy intake and %CR during weight loss necessitates either an early TEE measure to capture the rapid reduction in TEE during CR or appropriate weighting of the baseline and final TEE values to accurately reflect metabolic adaptations that accompany weight loss.