Prevalence of paradoxically normal serum cholestrol in morbidly obese women.

The paradox that cholesterol may be lower in extremely obese subjects versus those who are less overweight, although originally observed more than 40 years ago, has never been documented in a systematic fashion. We have therefore prospectively determined the body mass index (BMI) and serum cholesterol concentration in 3,312 women. The percentage of women with serum cholesterol in the normal range (<200 mg/dL) decreased with an increasing BMI, from 55% in women with a BMI less than 20 kg/m2 to 28% in those with a BMI of 30 to 35 kg/m2. Serum cholesterol greater than 300 mg/dL was found in only 2% of individuals with a BMI less than 20 kg/m2 but in 6% of the group with a BMI between 30 and 35 kg/m2. However, among morbidly obese women (BMI >40 kg/m2, n = 46), 39% presented with serum cholesterol less than 200 mg/dL and only one woman had serum cholesterol more than 300 mg/dL. With the BMI, the fitted regression model shows an increase in cholesterol for low BMIs, while cholesterol appears to decrease with larger values for the BMI. The age-dependent increase in cholesterol is more evident in younger women versus older women, where it tends to disappear. It is concluded that among morbidly obese women (BMI >40 kg/m2), there is a substantial subgroup with normal serum cholesterol.