Fat-Free Mass and Total Daily Energy Expenditure Estimated Using Doubly Labeled Water Predict Energy Intake in a Large Sample of Community-Dwelling Older Adults.

Background: Up to 30% of community-based older adults report reduced appetite and energy intake (EI), but previous research examining the underlying physiological mechanisms has focused on the mechanisms that suppress eating rather than the hunger drive and EI.

Objectives: We examined the associations between fat-free mass (FFM), physical activity (PA), total daily energy expenditure (TDEE), and self-reported EI in older adults.

Methods: The present study was a secondary analysis of the Interactive Diet and Activity Tracking in AARP study. Body composition (deuterium dilution), PA (accelerometry), and TDEE (doubly labeled water) were measured in 590 older adults (age, 63.1 ± 5.9 years; BMI, 28.1 ± 4.9 kg/m2). The total daily EI was estimated from a single 24-hour dietary recall (EIsingle; ±1 month of PA and TDEE measurement) and the mean of up to 6 recalls over a 12-month period (EImean), with misreporters classified using the 95% CIs between the EImean and TDEE.

Results: After controlling for age and sex, linear regression demonstrated that FFM and TDEE predicted EI when estimated from a single 24-hour dietary recall (P < 0.05), from the mean of up to 6 dietary recalls (P < 0.05), and after the removal of those classified as underreporters (P < 0.001). Age moderated the associations between FFM and EIsingle (P < 0.001), FFM and EImean (P < 0.001), and TDEE with EIsingle (P = 0.016), with associations becoming weaker across age quintiles.

Conclusions: These data suggest that the total daily EI is proportional to the FFM and TDEE, but not fat mass, in older adults. These associations may reflect an underling drive to eat that influences the daily food intake. While the associations between FFM or TDEE and EI existed across all age quintiles, these associations weakened with increasing age.