Energy Expenditure and Macronutrient Oxidation in Response to an Individualized Nonshivering Cooling Protocol

Abstract

Objective: This study aimed to describe the energy expenditure (EE) and macronutrient oxidation response to an individualized nonshivering cold exposure in young healthy adults. Methods: Two different groups of 44 (study 1: 22.1 [SD 2.1] years old, 25.6 [SD 5.2] kg/m2, 34% men) and 13 young healthy adults (study 2: 25.6 [SD 3.0] years old, 23.6 [SD 2.4] kg/m2, 54% men) participated in this study. Resting metabolic rate (RMR) and macronutrient oxidation rates were measured by indirect calorimetry under fasting conditions in a warm environment (for 30 minutes) and in mild cold conditions (for 65 minutes, with the individual wearing a water-perfused cooling vest set at an individualized temperature adjusted to the individual’s shivering threshold). Results: In study 1, EE increased in the initial stage of cold exposure and remained stable for the whole cold exposure (P < 0.001). Mean coldinduced thermogenesis (9.56 ± 7.9 kcal/h) was 13.9% ± 11.6% of the RMR (range: −14.8% to 39.9% of the RMR). Carbohydrate oxidation decreased during the first 30 minutes of the cold exposure and later recovered up to the baseline values (P < 0.01) in parallel to opposite changes in fat oxidation (P < 0.01). Results were replicated in study 2. Conclusions: A 1-hour mild cold exposure individually adjusted to elicit maximum nonshivering thermogenesis induces a very modest increase in EE and a shift of macronutrient oxidation that may underlie a shift in thermogenic tissue activity.