Cold induces increased ad libitum energy intake independent of changes in energy expenditure: a controlled crossover trial in adults

Abstract

Background: Measures of energy metabolism (energy expenditure [EE], respiratory exchange ratio [RER]) have been associated with ad libitum energy intake (EI) and weight gain in previous observational studies, suggesting that energy-sensing mechanisms drive EI to meet metabolic energy demands.

Objectives: We aimed to employ mild cold exposure as an intervention to alter energy metabolism and evaluate its causal effects on concurrent and next day ad libitum EI.

Methods: In a controlled crossover study, 47 volunteers (16 female; age 37.2 ± 10.7 y; body mass index 32.4 ± 8.6 kg/m²) completed four 24-h EE measurements in a respiratory chamber. Participants ate ad libitum for 24-h using an objective vending machine paradigm while in the chamber during both cold exposure (19°C) and thermoneutral conditions (23.5°C) and after 2 eucaloric chamber stays with exposure to each temperature. Energy metabolism changes were calculated from eucaloric conditions (cold compared with thermoneutral).

Results: Compared with thermoneutral conditions, participants consumed 13% more while residing in the chamber during cold (mean difference: 411 ± 987 kcal/d, P = 0.006), but not the day after cold exposure. Neither eucaloric EE, RER, nor carbohydrate oxidation (CARBOX) was significantly changed by cold exposure. However, greater increases in RER and CARBOX during cold exposure were associated with greater ad libitum EI on the day after cold exposure (r = 0.29, P = 0.049 and r = 0.33, P = 0.02), but not with EI during cold exposure. Cold-induced changes in 24-h EE were not associated with changes in ad libitum EI during or after cold exposure.

Conclusion: Ad libitum EI increased during but not after mild cold exposure. There was an effect of 24-h RER and CARBOX during cold exposure that was related to greater ad libitum EI after cold. These results indicate an acute effect of cold on concurrent EI independent of changes in metabolic rate, but also a residual influence of cold on subsequent EI via fuel preference. This trial was registered at clinicaltrials.gov as NCT02939404.

Keywords: RER; ad libitum food intake; adults; carbohydrate oxidation; catecholamines; cold-induced thermogenesis; core body temperature; lipid oxidation; plasma hormones; whole-room indirect calorimetry.

FIGURE 1

(A) Ad libitum energy intake assessed with a vending machine paradigm after eucaloric, eucaloric_cold, and during ad libitum and ad libitum_cold chamber visits. (B) Changes in ad libitum energy intake between eucaloric and eucaloric_cold chamber visits and ad libitum and ad libitum_cold chamber visits. One-sample t-test was used to determine whether the means of the differences were different from 0. Mean change and 95% confidence intervals (n = 47) are shown.

FIGURE 2

(A) Rates of 24-h energy expenditure (EE) during eucaloric, eucaloric_cold, ad libitum and ad libitum_cold chamber visits. (B) Changes in the rates of 24-h energy expenditure (EE) between eucaloric and eucaloric_cold chamber visits and ad libitum and ad libitum_cold chamber visits. One-sample t-test was used to determine whether the means of the differences were different from 0. Asterisk (∗) indicates P < 0.05. (C) Rates of 24-h respiratory exchange ratio (RER) during eucaloric, eucaloric_cold, ad libitum and ad libitum_cold chamber visits. (D) Changes in the rates of 24-h RER between eucaloric and eucaloric_cold chamber visits and ad libitum and ad libitum_cold chamber visits. One-sample t-test was used to determine whether the means of the differences were different from 0. Sample size: n = 47 for eucaloric and eucaloric_cold; n = 44 for ad libitum and ad libitum_cold.

FIGURE 3

Correlations between changes in ad libitum intake after eucaloric_cold chamber visits (compared with eucaloric chamber) and changes in (A) 24-h energy expenditure (EE), (B) respiratory exchange ratio (RER), (C) carbohydrate oxidation, (D) lipid oxidation, and (E) protein oxidation during eucaloric_cold chamber visits (compared with during eucaloric chamber). The strength of the associations was quantified by the Pearson correlation coefficient (r).

FIGURE 4

Plasma concentrations before and after the eucaloric_cold chamber visit and the difference between the 2 measurements for (A) secretin, (B) leptin, (C) ghrelin, and (D) FGF-21. Paired sample t-tests were used to compare whether measures differed between the 2 different conditions (e.g., before and after the chamber). Sample size: n = 47, except for ghrelin (n = 46). FGF-21, fibroblast growth factor 21.