Abstract
OBJECTIVE: The doubly labeled water (DLW) intake-balance method estimates energy intake (EI) during weight loss using the time-weighted average of total daily energy expenditure (TDEE) and changes in body energy stores. Because TDEE declines rapidly during the early phase of weight loss, an early additional measurement is recommended. This study aimed to develop regression models that estimate time-weighted TDEE using fewer interim measurements and determine if EI accuracy is maintained during a 12-month weight loss intervention. METHODS: Data from a behavioral weight loss intervention (Dietary Caloric Restriction versus intermittent Fasting Trial, "DRIFT") were used. TDEE, body weight, and body composition were measured at months 0, 1, 6, and 12. Regression models using only two or three time points were used to estimate time-weighted TDEE at months 6 and 12, respectively. Models were validated using bootstrap sampling, and time-weighted TDEE and percent caloric restriction (% CR) were compared to a reference approach. RESULTS: Models demonstrated strong predictive performance (R (2) = 0.911-0.982). Limits of agreement with the reference model were 121.1-274.5 kcal/day for TDEE and 4.5%-10.3% for % CR, without significant bias. CONCLUSIONS: Using a regression modeling approach, we demonstrate the DLW intake-balance method maintains accuracy during weight loss without early-phase TDEE measurements. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03411356.