The effects of a fat loss supplement on resting metabolic rate and hemodynamic variables in resistance trained males: a randomized, double-blind, placebo-controlled, cross-over trial

BACKGROUND While it is known that dietary supplements containing a combination of thermogenic ingredients can increase resting metabolic rate (RMR), the magnitude can vary based on the active ingredient and/or combination of active ingredients. The purpose of this study was to examine the effects of a commercially available thermogenic fat loss supplement on RMR and hemodynamic variables in healthy, resistance trained males. METHODS Ten resistance-trained male participants (29 ± 9 years; 178 ± 4 cm; 85.7 ± 11 kg, and BMI = 26.8 ± 3.7) volunteered to participate in this randomized, double-blind, placebo controlled cross-over study. Participants underwent two testing sessions separated by at least 24 h. On their first visit, participants arrived to the laboratory after an overnight fast and a 24-h avoidance of exercise, and underwent a baseline RMR, HR, and BP assessment. Next, each participant ingested a thermogenic fat loss supplement (TFLS) or a placebo (PLA) and repeated the RMR, HR, and BP assessments at 60, 120, and 180 min post-ingestion. During the second visit the alternative supplement was ingested and the assessments were repeated in the exact same manner. Data were analyzed via a 2-factor [2x4] within-subjects repeated measures analysis of variance (ANOVA). Post-hoc tests were analyzed via paired samples t-tests. The criterion for significance was set at p ≤ 0.05. RESULTS A significant main effect for time relative to raw RMR data (p = 0.014) was observed. Post-hoc analysis revealed that the TFLS significantly increased RMR at 60-min, 120-min, and 180-min post ingestion (p < 0.05) as compared to baseline RMR values. No significant changes in RMR were observed for the PLA treatment (p > 0.05). Specifically, RMR was increased by 7.8 % (from 1,906 to 2,057 kcal), 6.9 % (from 1,906 to 2,037 kcal), and 9.1 % (from 1,906 to 2,081 kcal) in the TFLS, while the PLA treatment increased RMR by 3.3 % (from 1,919 to 1,981 kcal), 3.1 % (from 1,919 to 1,978 kcal), and 2.1 % (from 1,919 to 1,959 kcal) above baseline at 60, 120, and 180-min post ingestion, respectively. Additionally, the TFLS significantly elevated RMR at the 3-h time point as compared to the PLA treatment (2,081 vs 1,959 kcal, p = 0.034). A main effect for groups was observed for systolic blood pressure, and a significant interaction and main effect for time were observed for diastolic blood pressure. It should be noted that although changes in diastolic blood pressure were significant, all values stayed within normal clinical ranges (<80 mmHg). CONCLUSIONS The TFLS led to significant elevations in RMR as compared to baseline. These elevations came with no adverse effect relative to resting heart rate, but a slight increase in blood pressure values. Taken on a daily basis, this TFLS may increase an individual's overall energy expenditure, however; future studies should investigate if this leads to a reduction in fat mass loss over time.