Ergometric performance and cardiovascular profile of obesity clinic patients

BACKGROUND: Aerobic exercise capacity is considered as an independent prognostic factor for cardiovascular disease and mortality. It is usually expressed in maximal oxygen consumption (VO2(max)) or metabolic equivalent (MET) and is measured by spiroergometry or calculated by a regression formula based on maximal performance achieved. Obesity is associated with reduced physical performance and increased cardiovascular mortality. The aim of our study was to describe the ergometric and cardiovascular profile of patients of an obesity clinic, and to compare a direct measure of VO2(max) with an indirect by a regression formula and to.

METHOD: 131 consecutive patients of an obesity clinic (95 females, 36 males) aged 16-75 years participated. The VO2(max) was measured by spiro-ergometry on a treadmill and estimated by a regression formula on the basis of the speed and grade of the treadmill. We have determined the relationship between Body mass index (BMI), Waist Circumference (WC) and the parameters VO2(max)/kg, MET, Performance Relative for Age, Heart Rate Recovery one minute after maximal effort (HRR), VO2(max) relative to a theoretical normal body weight (corresponding to a BMI of 25 kg/m2 (VO2(max)Rel25)), blood pressure, at rest and 5 minutes after exercise, Framingham Score and C-reactive protein (CRP).

RESULTS: For the different age groups the VO2(max)/kg was below normal values (mean -23.4%). Measured VO2(max) was 15.2% lower than estimated by the regression formula. After adjusting to age and to a theoretical upper-limit normal body weight (corresponding to a BMI of 25 kg/m2) VO2(max)/kg was 5-20% (mean value 15%) higher than the reference values. VO2(max)/kg and HRR were correlated with BMI, WC and Framingham Score. 40% of the patients were already treated for hypertension, 55% had elevated blood pressure measurements at rest and 52% after exercise.

CONCLUSIONS: Ergometric stress testing in obese subjects delivers important information that helps to evaluate the cardiovascular risk in this population and to provide individual recommendations for training therapy (e.g. training intensity, heart rate etc). Obese patients show a marked diminution of aerobic exercise capacity. In this population, the use of a standard regression formula to calculate VO2(max) leads to an overestimation of aerobic performance. The even higher than normal VO2(max) related to upper-normal body weight indicates that the reduced physical performance in obese patients is rather due to the overweight than to a pathological loss of muscle mass.