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 cold‐induced 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.

Validity of four commercially available metabolic carts for assessing resting metabolic rate and respiratory exchange ratio in non-ventilated humans

“…Twelve-hour urine samples (i.e., starting the collection immediately after the dinner and continuing it during the fasting period) were collected before arriving to the research center. Total urine volume and urea concentration, by an enzymatic method (Spinreact, UREA-37_R1, Girona, Spain), were measured and urinary nitrogen estimated using a regression equation [22]. Estimated nitrogen urine concentration was multiplied by the urine volume and divided by the time of sample collection.…”

Adults with metabolically healthy overweight or obesity present more brown adipose tissue and higher thermogenesis than their metabolically unhealthy counterparts

“…Urinary nitrogen concentration was estimated from urea concentration following the equation “Nitrogen (g/l) = 0.0065∗ Urea (mg/dl) + 1.2598” obtained from a linear regression including urea and nitrogen measured concentrations from 20 participants. 28 Energy expenditure was estimated from oxygen consumption, carbon dioxide production, and estimated urinary nitrogen excretion rate, using Weir's abbreviated equation. 29 Unfortunately, due to problems with data collection (e.g., unavailability of the metabolic cart, error in calibration, etc.)…”