Background: Weight loss supplements are widely advertised and highly sought out products. Many supplements claim to increase body fat utilization, increase resting metabolic rate (RMR), and to improve body composition by decreasing total body fat composition. Therefore, the purpose of this study was to determine the acute effect of nonstimulant herbal supplements on RMR and substrate utilization.
Methods: Ten female and 16 male participants (mean age 23.7 ± 3.9 years; mean weight 79.2 ± 18.2 kg) completed a random-repeated measures crossover study. Participants completed a total of three RMRs by either ingesting a placebo (P) or one of two supplements [raspberry ketones (R) or metabolic activator blend (MAB)] 2 hours prior to testing.
Results: No significant difference was found for RMR for P vs. MAB (p = .130), vs. R (p = .588), and MAB vs. R (p = .636). No significant difference was found for respiratory quotient for P vs. MAB (p = .056), vs. R (p = .149), and MAB vs. R (p = .764). No significant difference was found for substrate utilization: percent carbohydrate utilization, P vs. MAB (p = .052), P vs. R (p = .124), and MAB vs. R (p = .680); and percent fat utilization, P vs. MAB (p = .052), P vs. R (p = .120), and MAB vs. R (p = .749).
Conclusions: Therefore, nonstimulant weight loss supplements may not be beneficial for weight loss, or an increase of fat utilization.
Keywords: herbal supplements; metabolic rate; weight loss.