Mariana V. Jacobs, Trey R. Naylor, Justin Pol, Michael Samaan, Jody L. Clasey, FACSM. University of Kentucky, Lexington, KY.

BACKGROUND: It has been previously reported that obese individuals have greater absolute and lower relative oxygen consumption measures compared to their healthy-weight counterparts during constant load exercise. However, the method of determining obesity status may significantly influence the results and conclusions of group comparisons. The purpose of this study was to compare the influence of classification methodology by using body mass index (BMI kg • m-2) and body fat percentage (%Fat) to assess oxygen consumption rates (VO2) during submaximal, constant load exercise. METHODS: Seventeen participants (F:8, Age 23.4 ± 2.7yrs) completed a 30-minute walking task on a treadmill at a constant self-selected speed while wearing a portable metabolic system to measure relative VO2 (mL• kg-1 • min-1). All participants underwent a total body DXA scan to assess %Fat. Participants were categorized as healthy (H) or obese (O) using two methods: 1) %Fat (World Health Organization; WHO) and 2) BMI. WHO guidelines indicate healthy %fat for females and males as 21-32% and 8-19%, respectively, with obese classified as those that exceed these sex specific ranges. A BMI of <30 kg • m-2 and >30 kg • m-2 were used to categorize participants as healthy and obese, respectively. Unpaired t-tests (p<0.05) were used to assess between group differences as a function of categorization (WHO vs. BMI). Dependent variables included: walking speed (m • s-1), VO2 at the start (T0), end (T30), the change of VO2 (ΔVΟ2; T30-T0) and total VO2. RESULTS: When using BMI as classification criteria (H:11, O:6), obese participants had significantly lower VO2 at T0 (p<0.01) and T30 (p=0.01), leading to a significantly lower total VO2 (p=0.01). Additionally, the obese participants walked at a 17.5% slower speed (p=0.04). When classified using the %Fat (H:8, O:9), healthy and obese participants walked at similar speeds (p=0.20) yet the obese group displayed trends of lower VO2 at T0 (p=0.07) and T30 (p=0.07) as well trends of lower total V02 (p=0.07). The ΔVΟ2 was similar between groups regardless of using the %Fat (p=0.44) or BMI (p=0.42) criterion. CONCLUSION: These results concur with previous results that in obese individuals, relative VO2 is lower when compared to healthy weight individuals during constant load exercise, despite criterion used. Future research will explore additional ways to classify participants for group comparative purposes.

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