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Scaling V o 2 Peak in Obese and Non‐obese Girls

2001; Wiley; Volume: 9; Issue: 5 Linguagem: Inglês

10.1038/oby.2001.36

1550-8528

Mark Loftin, Melinda Sothern, Laura Trosclair, Ann O’Hanlon, James Miller, John N. Udall,

Obesity, Physical Activity, Diet

Abstract Objective: The conventional ratio method (milliliters O 2 per mass) typically is used to express V o 2 peak. The goal of the current study was to compare V o 2 peak of obese girls with normal‐weight girls by ratio and allometric scaling methods. Research Methods and Procedures: We compared V o 2 peak by ratio and allometric methods in 46 obese and 47 normal‐weight girls. Indirect calorimetry was used to measure V o 2 peak during either treadmill running or walking. Regression analysis was used to determine coefficients for mass and stature for each group with ANOVA used to compare data between groups. Results: The obese girls were taller and had higher values of body fatness ( p ≤ 0.05). Absolute V o 2 peak (liters per minute) was similar between groups ; however V o 2 peak relative to mass was 50% lower ( p ≤ 0.05) in the obese girls. When V o 2 peak (milliliters per minute per kilogram) and mass were correlated, r = −0.48 was found in the obese group. Allometric scaling of logarithmic transformed stature and mass reduced this to r = −0.002, thus eliminating the bias associated with the ratio method. Adjusting V o 2 peak allometrically scaled for mass, stature, and the combination of mass and stature reduced the difference between groups from 50% (ratio method) to 10% to 11% ( p ≤ 0.05) with higher values found in the normal‐weight girls. Discussion: These results demonstrate the bias associated with the ratio method when comparing V o 2 peak in obese girls with V o 2 peak in normal‐weight girls. Allometric scaling eliminated the bias and thus may reflect a truer comparative response.