Background

We have demonstrated that a lesser decrease in 24h energy expenditure (24EE) during fasting from energy balance (ENBAL) predicts resistance to weight gain during overfeeding or greater weight loss during caloric restriction indicating a spendthrift phenotype. The change in 24EE to cold exposure (CE) may similarly predict weight changes. The aim of this study was to determine whether using ENBAL during 24EE as a baseline, greater increase inCE is associated with less decrease in 24EE during fasting.

Methods

In 20 healthy subjects, 24EE was measured in a whole-room indirect calorimeter during ENBAL both at thermoneutrality (ambient temperature: 23.6±0.3°C, mean±SD) and mild CE conditions (19.0±0.3°C), and during fasting at thermoneutrality (23.6±0.3°C). Body composition was assessed by DXA. During all 24EE assessments, central/peripheral skin temperature and core body temperature (CBT) were continuously measured by iButtons and swallowable CorTemp sensors, respectively.

Results

During CE, peripheral and central skin temperature decreased by 0.8±0.8°C (p=0.001) and 0.4±0.6°C (p=0.03) while CBT remained constant (p=0.09). Compared to ENBAL, average 24EE during CE remained unchanged but showed a high inter-individual variability (−25±96 kcal/day, p=0.26). During fasting, peripheral and CBT remained unchanged (all p>0.23) while central skin temperature increased (+0.2±0.4°C, p=0.03). Compared to ENBAL, average 24EE during fasting decreased by 162±127 kcal/day (p<0.0001). A greater increase in 24EE during CE was associated with less decrease in 24EE during fasting (r=0.84, p<0.0001). This remained so when controlling for 24EE during ENBAL (partial r=0.83, p<0.0001) and after adjustment for body composition measures (r=0.84, p<0.0001).

Conclusions

Greater AT during CE was closely related to less decrease in 24EE during fasting. Thus, CE further defines the spendthrift phenotype providing additional measures to investigate the mechanism by which these dynamic changes in 24EE affect weight change.