Background

The prevalence of obesity is rising globally, independent of ethnicity, race and age, and is associated with increased mortality and morbidity Several lines of evidence indicate that the distribution of fat is a major determinant of cardiovascular risk in both normal weight, overweight and moderately obese subjects, although measures of general obesity and physiological differences between genders must also be considered.

Only a few studies in morbidly obese subjects have compared the effect of overall and central obesity on cardiovascular risks and the results have been inconsistent both within, and between genders. Nevertheless, obesity is a major modifiable risk factor for coronary artery disease (CAD) that imparts a degree of cardiovascular risk similar to that associated with hypertension, hyperlipidemia, smoking and sedentary lifestyle. Accordingly, it seems to be a paradox that the increasing obesity rates coincide with a decreased risk of cardiovascular death.

Methods

Study design
This is an analysis of cross-sectional baseline data from a non-randomized clinical trial comparing the effects of a comprehensive lifestyle modification program and bariatric surgery on arterial stiffness in morbidly obese patients. (http://ClinicalTrials.gov website Identifier NCT00626964).

Setting
The study was performed at a tertiary care centre (the Morbid Obesity Centre, Vestfold Hospital Trust, Tønsberg, Norway)

Participants and study size 
The patients in the intensive lifestyle intervention group were all selected from patients that had signed up for participation in a standardized health promoting and weight reductive program at the hospital for rehabilitation. Participants in the surgery group were selected from patients preparing for bariatric surgery at our hospital. Patients with one of the following conditions or diseases were excluded; uncompensated heart failure, cardiac arrhythmias, unstable angina, end-stage renal disease, known bleeding disturbances, serious psychiatric disorders, serious eating disorders, cardiac pacemakers, intra-cardiac devices, cerebrovascular event or a myocardial infarction within the last six months. The study was approved by the regional ethics committee of the Southern Norway Regional Health Authority, and was performed in accordance with the Declaration of Helsinki

Variables
The main outcome variable was arterial stiffness measured by PWV. The main explanatory variables were various measures and estimates of body composition, including anthropometric characteristics (WC, WHR, WHtR, and BMI), data from bioelectrical impedance analysis (BIA) [visceral fat area (cm2), fat mass (kg) and fat free mass (kg)].

Data sources and measurements
All participants underwent a medical examination performed by a physician and a trained nurse. Blood was collected by venipuncture following an overnight fast on the day of medical examination. Weight and height were measured with patients wearing light clothing and no shoes. BMI was calculated as weight in kilograms divided by the square of the height in meters. WC (cm) was measured midway between the 12th rib and the iliac crest. Blood pressure was measured after five minutes of rest using an electronic auscultatory blood pressure recorder with an appropriately sized cuff based on the measurement of arm circumference with the patient sitting in the upright position.

Pulse wave velocity
The measurement of PWV is generally accepted as the simplest, non-invasive, robust, and reproducible method to determine arterial stiffness and is considered to be the gold standard method

Results

Women
In the female group, PWV was positively correlated with BMI, WC and WHtR.  PWV was significantly correlated with visceral fat area, fasting glucose, HbA1c and the usage of β-blockers and calcium-channel blockers.

Men
In the male group, PWV showed a significant negative correlation with BMI (Figure 1). The use of calcium-channel blockers, inhibitors of the RAA-system, statins and fasting glucose were positively correlated with PWV

Conclusion
Most measures of general and abdominal obesity were associated with arterial stiffness in morbidly obese women.

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