Participants

Ten healthy males (age: 29 ± 9 years; height: 178 ± 4 cm; bodyweight: 85 ± 11 kg; BMI: 26.8 ± 3.7) between the ages of 18 and 50 years volunteered to participate in this randomized, double-blind, placebo controlled cross-over study. All participants reported engaging in resistance exercise an average of four days per week. The research protocol was approved by the University of South Florida Institutional Review Board. Following an explanation of all risks and benefits associated with the experimental protocol, each participant gave his informed consent to participate in this study. Participants were screened for participation based on established criteria set forth by the American College of Sports Medicine [26]. In order to participate in the study, participants needed to be free from cardiovascular, pulmonary, and metabolic disease. Participants that were categorized as ‘high risk’ for cardiovascular disease according to the American College of Sports Medicine’s risk stratification were excluded from participation in the study. Participants were also excluded as a result of any intolerance or known allergy to the supplement ingredients.

Experimental design

The study utilized a randomized, double blind, placebo controlled crossover design. Participants reported to the Performance and Physique Enhancement Laboratory following an overnight fast (a minimum of an 8-h fast) and a 24-h avoidance of exercise on two occasions separated by at least 24 h. The laboratory was climate controlled throughout the duration of the study with the following recorded variables: temperature = 21.3 °C; humidity = 50.4 %; and barometric pressure = 762 mmHg. After arriving to the laboratory, a coin was flipped to randomly determine the order of the dietary supplement ingestion. If the participant were randomized to ingest the thermogenic fat loss supplement (Iron Cuts™) on the first testing session, they would ingest the alternate treatment (placebo) on the second and final testing session. Likewise, if the participant were randomized to ingest the placebo treatment on the first testing session, they would ingest the alternate treatment (Iron Cuts™) on the subsequent laboratory visit. Testing sessions for both laboratory visits occurred between the hours of 6:30 am and 8:00 am, with the majority of all assessments beginning at 7 am.

Testing sessions

Upon arriving to the laboratory, participants were encouraged to visit the restroom to void their bladders of urine. Next, body weight was measured on a physician beam scale (Health-O-Meter™, Model 402KL, McCook, IL, USA) and then the participant sat in a reclined position with their feet elevated for a 5-min period. After sitting quietly for 5 min, participants had their resting heart rate and blood pressure recorded using an automated, oscillometric blood pressure monitor (Omron 5 series Model BP742, Lake Forest, IL, USA). This method of automated, oscillometric blood pressure measurement has been validated in the scientific literature [27]. Heart rate and blood pressure were measured in triplicate and the average of the three readings was recorded.

Next, the participant remained in a reclined position for an additional 5 min prior to the resting metabolic rate (RMR) measures. All RMR measures were made using a Cosmed FitMate Pro™ (Cosmed, Italy). The FitMate Pro™ contains a turbine flow meter for measuring ventilation and a galvanic fuel cell oxygen sensor for analyzing the fraction of oxygen in the expired gases. To sample the expired air, a facemask was placed over the participant’s face and was attached to the turbine flow meter. The device uses standard metabolic formulas to calculate oxygen uptake, and energy expenditure is calculated using a fixed respiratory quotient (RQ) of 0.85. The FitMate Pro™ also conducts a self-calibration before each measurement, and at two other times (5 and 10 min) during the 15-min RMR assessment. The device has been validated with a Douglas bag for non-obese and obese subjects and was found to calculate RMR accurately (r = 0.97, p = 0.579) [28]. Intra and inter-day test-retest correlation calculated for the device used in the present study were as follows: intra-day RMR Pearson correlation was r = 0.96 (p < 0.01) and the inter-day RMR Pearson correlation was r = 0.90 (p < 0.01). Intra-day RMR ICC was 0.981 and the inter-day RMR ICC was 0.946.

At baseline, two consecutive RMR tests were conducted and the lower of the two measured RMR values was recorded as the baseline RMR value. During the RMR test, the participant was instructed to relax during the test, to breathe normally, and to remain as still as possible for the duration of the 15-min test. The first 5 min of data collection was discarded [29] and the final 10 min of data collected was used in the calculation of the resting metabolic rate.

After baseline RMR was established, the participant ingested three capsules of either the thermogenic fat loss supplement (Iron Cuts™) or placebo treatment. After ingestion of the supplement treatments, three more heart rate, blood pressure, and RMR assessments were conducted at 1-h, 2-h, and 3-h post ingestion. Figure 1 presents an overview of the study test sessions.

Fig. 1 Overview of testing sessions Full size image

Supplement

The thermogenic fat loss supplement (Iron Cuts™) treatment and placebo were ingested in capsule form, and three capsules were ingested per dose. Capsules were identical in appearance and taste. The ingredients in the thermogenic fat loss supplement treatment (Iron Cuts™) are presented in Table 1, while the placebo contained only inert ingredients (650 mg of maltodextrin and 88.8 mg of hemp protein). Following the completion of two baseline RMR tests, the participant ingested three capsules of the thermogenic fat loss supplement or the placebo treatment with eight ounces of water. Supplement ingestion was in the presence of research personnel for all testing sessions.

Table 1 Thermogenic Fat Loss Supplement Ingredients Full size table

Statistical analysis

Statistical analyses of the data were analyzed via a 2-factor treatment by time [2x4] within-subjects repeated measures analysis of variance (ANOVA) using SPSS version 22.0. If sphericity could not be assumed, a Huynd-Feldt correction was used to produce a more critical F-value. Post-hoc tests (comparisons between treatments at each time point [baseline and 60-min, 120-min and 180-min post ingestion and comparisons of post-supplement ingestion with baseline measures within each treatment) were analyzed via paired samples t-tests. Incremental area under the curve (AUC) was calculated for each treatment (thermogenic supplement and placebo) using the trapezoidal method as described by Brouns et al. [30]. AUC was determined by measuring the increase in RMR above baseline over the three-hour assessment period. A paired samples t-test was used to determine AUC differences between the two treatments. A criterion α-level of p ≤ 0.05 was used to determine statistical significance.