Feasibility, reproducibility, and cold-induced energy expenditure using whole-room calorimetry in adults and children

To understand energy balance, whole-room indirect calorimetry (WRIC) allows for accurate measurement of energy expenditure (EE).

To examine the relationship between cold-induced resting EE and brown adipose tissue (BAT) activity measured by magnetic resonance imaging (MRI) and to evaluate WRIC system (WRICS) performance and feasibility of use in children and adults.

The WRICS was equipped with a Promethion High-Definition Room Calorimetry System. Technical validation utilized nitrogen (N₂) and carbon dioxide (CO₂) gas infusions. Healthy adults (n = 21) and children aged 8-17 years (n = 17) attended two 4-hour WRIC visits (one week apart) and one MRI visit. Resting EE at 25 °C (REE₂₅) was compared between visits and to REE at 18 °C (REE₁₈). Recruitment and completion rates were examined. BAT activity was assessed by MRI as the decline in supraclavicular proton density fat fraction during 18 °C cold exposure.

Gas infusion testing confirmed high accuracy (respiratory exchange ratio [RER] = 0.99; 95% CI 0.991-0.996). Study completion rates were high (adults: 20/21; children: 17/18). REE₂₅ over a 10-minute period was consistent between visits (adults: 1.68 ± 0.462 vs 1.66 ± 0.301 kcal/min, P = 0.77; children: 1.50 ± 0.358 vs 1.58 ± 0.348 kcal/min, P = .25). Cold exposure increased fasting EE by 0.21 kcal/min (adults) and 0.14 kcal/min (children). BAT activity was correlated with REE₁₈ in adults (r = 0.49, P = .04).

WRICS use was feasible in adults and children. Changes in EE during cold (ie, cold-induced thermogenesis) were measurable and related to BAT activity, supporting the usefulness of this system in the assessment of EE in response to interventions in adults and children.