Risk for obesity-related diseases not high for all obese individuals

According to researchers, some normal-weight individuals experience a clustering of cardiometabolic abnormalities.

Issue: September 2008

Obesity may not always lead to early atherosclerosis or clustering of cardiometabolic abnormalities, according to data from two studies recently published in the Archives of Internal Medicine.

“Currently, almost every clinician is facing the epidemic of obesity and seeing more and more obese people at risk for developing diseases like cardiovascular disease and diabetes,” Norbert Stefan, MD, Heisenberg-Stipendium, department of internal medicine IV, University of Tübingen, told Endocrine Today. “The question is, is it possible to identify the people with the highest obesity-related disease risk?”

Stefan and colleagues conducted a study to identify people with metabolically benign obesity and determine the characterizing factors. The study included 314 participants aged 18 to 69 years.

Participants were divided into four groups based on weight: normal (BMI<25), overweight (BMI 25-29.9), obese-insulin sensitive (BMI ≥30 and placement in the upper quartile of insulin sensitivity) and obese-insulin resistant (BMI ≥30 and placement in the lower three quartiles of insulin sensitivity).

Compared with the normal weight group, those in the overweight and obese groups had higher total body and visceral fat (P<.05), but the researchers reported no difference between the obese groups.

Compared with the obese-insulin resistant group, the obese insulin-sensitive group had lower ectopic fat in skeletal muscle (P<.001) and liver (4.3% vs. 9.5%) and lower intima-media thickness of the common carotid artery (0.54 mm vs. 0.59 mm). Insulin sensitivity was higher in this group (P<.05).

Participants in the obese-insulin sensitive and normal-weight groups had nearly identical insulin sensitivity (18.2 AU) and insignificant differences in intima-media thickness (0.51 mm), according to the researchers.

“Simply looking at BMI as an obesity parameter is not enough to classify one’s risk for obesity-related diseases. It is important to look at the waist circumference, which seems to separate those with high and low risk,” Stefan said.

Based on these data, the researchers concluded that ectopic liver fat may be more beneficial than visceral fat in determining a metabolically benign phenotype in obesity.

Obesity and cardiometabolic risks

In a second study, researchers from Albert Einstein College of Medicine and other sites in New York, California and Michigan found a high prevalence of overweight and obese people who are metabolically healthy, and a high prevalence of normal-weight individuals who experience a clustering of cardiometabolic abnormalities.

Using data from the NHANES study, the researchers assessed the prevalence and correlates of combined BMI and cardiometabolic groups (metabolically healthy, zero or one cardiometabolic abnormalities; and metabolically abnormal, ≥2 cardiometabolic abnormalities) in 5,440 participants.

Cardiometabolic abnormalities were defined as elevated blood pressure; high levels of triglycerides, fasting plasma glucose and C-reactive protein; elevated homeostasis model assessment of insulin resistance value and low HDL level.

In the normal-weight group, 23.5% were metabolically abnormal, according to the researchers. They also found that 51.3% of participants in the overweight group and 31.7% in the obese group were metabolically healthy.

Among normal-weight participants, independent relationships of clustering of cardiometabolic abnormalities were older age, lower levels of physical activity and larger waist circumference. Among overweight and obese participants, younger age, non-Hispanic black race/ethnicity, higher levels of physical activity and smaller waist circumference were independently related to having zero or one cardiometabolic abnormality.

Arch Intern Med. 2008;168:1609-1616.

Arch Intern Med. 2008;168:1617-1624.