# Effect of Using the Food Quotient as a Proxy of the Respiratory Quotient in the Calculation of Energy Expenditure by the Doubly Labeled Water Method in Older Adults

## TL;DR

This study compares different methods to estimate energy expenditure in older adults and finds that using food quotient from self-reported diets slightly underestimates energy needs compared to other methods.

## Contribution

The study evaluates the impact of using food quotient from self-reported diets as a proxy for respiratory quotient in energy expenditure calculations in older adults.

## Key findings

- DLW-TEE calculated with FQ significantly reduced TEE compared to RQ-0.85 values by −45 kcal/day.
- DLW-TEE did not differ significantly between sexes when using RQ approaches.
- TEE estimates using FQ, RQ-IC, and RQ-0.85 showed modest differences that could lead to overestimation of energy requirements over time.

## Abstract

Accurate measurement of total energy expenditure (TEE) is critical for maintaining energy balance and body weight. This study aimed to analyze differences in TEE assessed by the doubly labeled water method (DLW‐TEE), using food quotient (FQ) derived from self‐reported 24‐h dietary recalls, respiratory quotient measured by indirect calorimetry (RQ‐IC), and usual respiratory quotient of 0.85 (RQ‐0.85) based on Western‐type diet intakes.

Secondary analysis from a cross‐sectional study conducted in a sample of 41 independent (21 women) older people (≥ 60 years). FQ was obtained from three self‐reported 24‐h dietary recalls, RQ‐IC was measured after an overnight fast under resting conditions. Repeated measures analysis of variance was used to compare differences in DLW‐TEE calculated with FQ, RQ‐IC, and RQ‐0.85.

DLW‐TEE was significantly different between the three approaches (p = 0.025). The RQ approaches on DLW‐TEE did not differ significantly between sexes (p = 0.325). The overall mean DLW‐TEE RQ‐0.85 was 2253 (SD = 529, 95% CI: 2086, 2420) kcal/day, DLW‐TEE RQ‐IC was 2251 (SD = 541, 95% CI 2090, 2431) kcal/day, and DLW‐TEE FQ was 2208 (SD = 534, 95% CI 2039, 2376). DLW‐TEE calculated with FQ significantly reduced TEE compared to the mean DLW‐TEE with RQ‐0.85 values (ΔTEE −45 kcal/day, p < 0.001).

Self‐reported dietary intake data may provide a more context‐specific estimate of the FQ than relying solely on RQ from indirect calorimetry or the fixed RQ of 0.85 in DLW‐based TEE calculations. Although the resulting differences in TEE are modest, they can lead to overestimation of energy requirements over time.