Abstract 1616: Measures of Obesity and Cardiovascular Risk: Is BMI or Waist Circumference the Preferred Metric in Patients Who Have Undergone Gastric Bypass Surgery?
Background: Obesity is a strong risk factor for coronary artery disease. However, there is debate as to which measures of obesity (e.g. body mass index (BMI) vs. waist circumference) are most useful for cardiovascular risk assessment. The issue is even more complicated in severely obese subjects who have undergone gastric bypass surgery (GBS) since visceral and peripheral fat depots are affected differently.
Methods: A subset of subjects (n=138) enrolled in a prospective study of severely obese subjects treated with GBS or nonsurgical therapy (Nonsurg), underwent noncontrast CT scanning of the abdomen at L4 –5 to quantify visceral fat 5 years after initial enrollment. They had concomitant measurements of BMI, waist and hip circumferences and serum lipids.
Results: Age at the 5-year visit was 50±9 vs. 53±10 yrs in GBS and Nonsurg. 77% were female. Participants in the GBS group (n=62) had a decrease in BMI from 46.5 kg/m^2 at baseline to 32.4 at 5 years while the Nonsurg group (n=76) did not change (44.6 to 44.9). At 5 years, waist circumference was 105±20 cm vs. 138±21 cm and visceral fat volume was 54±39 cc vs. 144±63 cc in GBS and Nonsurg subjects, respectively. In general, visceral fat volume measured by CT correlated much better with anthropometrics in the GBS subjects vs. the Nonsurg subjects (Table⇓). Waist circumference correlated better with components of the metabolic syndrome (systolic BP, and serum triglycerides) in GBS than in Nonsurg subjects. Interestingly, visceral fat volume also correlated better with triglycerides in GBS than in Nonsurg subjects.
Conclusions: Measures of waist circumference are good markers of visceral fat volume and metabolic syndrome in subjects who have undergone GBS. However, waist circumference is not an accurate predictor of visceral fat or metabolic complications in untreated obese. Simple measures of body size or dimensions are probably not adequate to fully predict cardiovascular risk in a severely obese population.