Influence of Ambient Temperature on Resting Energy Expenditure in Metabolically Healthy Males and Females.

BACKGROUND

It is not yet clear to what extent the physiologic regulatory mechanisms that maintain core body temperature are reflected by changes in resting energy expenditure (REE). Particularly, in indirect calorimetry with a canopy, the effects of short-term temperature exposures have not yet been investigated. This can be of relevance for the determination of REE in practice.

OBJECTIVES

This randomized crossover study investigated the influence of a 30-min exposure to 18 °C (cool room temperature), 22 °C (room temperature), 28 °C (thermoneutral zone), and 38 °C (heat) on REE determined by assessing the inhaled oxygen volume and the exhaled carbon dioxide volume via indirect calorimetry on 4 consecutive days.

METHODS

In total, 32 metabolically healthy participants [16 males and 16 females, age: 25 ± 3 y, body mass index (BMI): 22.4 ± 1.6 kg/m2] were included in the study after screening examination.

RESULTS

Lean body mass, ambient temperature, and heart rate were the most important determinants (all P < 0.001) and explained 61.3% of the variance in REE. A multivariate linear mixed model analysis revealed that lean mass (15.87 ± 3.66; P < 0.001) and ambient temperature (P = 0.001) significantly influenced REE. REE significantly differed between 18 and 28 °C (18 °C: +96 ± 24 kcal/24 h; P < 0.001), 22 and 28 °C (22 °C: +73 ± 24 kcal/24 h; P = 0.003), and 18 and 38 °C (18 °C: +57 ± 23 kcal/24 h; P = 0.016).

CONCLUSIONS

Effects of ambient temperature on REE, especially cold, are detectable after only brief exposure, emphasizing the importance of performing indirect calorimetry with a canopy under controlled environmental conditions. The study was registered at clinicaltrials.gov as NCT05505240 (Influence of Ambient Temperature on Resting Energy Expenditure of Healthy Adults - Full Text View - ClinicalTrials.gov).