The Effect Of Thermogenic Nutritional Supplementation On Resting Metabolism In College-age Females

Abstract

BACKGROUND: Global increases in the incidence of obesity and the ensuing clinical co-morbidities has increased interest in the use of thermogenic supplements formulated to increase resting metabolism to increase energy expenditure and fat utilization. PURPOSE: The purpose of this study was to assess the effect of new capsaicin-based thermogenic supplements on resting oxygen consumption (VO2), carbon dioxide production (VCO2) and respiratory quotient (RQ). METHODS: Twenty-two untrained females (21.1±4.2 years) visited the lab on six occasions for measurements of pre-supplementation (PRE) resting energy expenditure (REE) for 30-60 min followed by the ingestion of a placebo or supplement (Shred, Shred 2.0, Capsimax 50, Capsimax 100, Capsimax 200) with at least three days separating conditions. Resting VO2, VCO2, and RQ were re-assessed for 90-120 minutes post-supplementation (POST). Changes in metabolic markers between treatment groups and over time were assessed in 5-minute intervals over the course of the 90-minute assessment using a two-way repeated measures ANOVA. RESULTS: PRE VO2 (2.5 ± 0.3 ml•kg-1•min-1; 0.21±0.03 L•min-1), VCO2 (0.18 ± 0.03 L•min-1), and RQ (0.85 ± 0.06) were lower than any given 5-minute interval POST (p<0.05). VO2 (ml•kg-1•min-1) was elevated at 5 min POST (2.99 ± 0.5 ml•kg-1•min-1) compared to each subsequent 5 min interval (p<0.05) with no differences noted after 10 minutes (2.7 ± 0.4 ml•kg-1•min-1). VCO2 and VO2 (L•min-1) were elevated at 5 min POST compared to subsequent 5-minute intervals until 80 min (VCO2; 0.22 ± 0.04 to 0.19 ± 0.03 L•min-1) and 70 min (VO2; 0.25 ± 0.04 to 0.23 ± 0.03 L•min-1; p<0.05). There were no changes in VCO2 at 10 minutes (0.19 ± 0.03 L•min-1) compared to any other time point POST. VO2 (L•min-1) briefly increased from 35-45 minutes POST (0.23 ± 0.04 L•min-1) compared to 20 min POST (0.22 ± 0.03 L•min-1; p=0.002); no further changes occurred after 45 minutes. There were no changes in RQ during POST. There were no interaction effects (time*treatment) or treatment differences in metabolic markers. CONCLUSIONS: Observed time effects are postulated as a result of the elevated REE caused by changes in subject position during supplement consumption, rather than supplementation. This study suggests that new thermogenic supplementation has no effect on metabolism.