Last Updated: 2002-09-03 17:00:14 -0400 (Reuters Health)

By Suzanne Rostler

NEW YORK (Reuters Health) - Although obesity is a major risk factor for heart disease, insulin resistance--a precursor to diabetes--may play a more central role, researchers report.

Their study found that obese people who were not insulin-resistant did not have an elevated risk of heart disease. Conversely, study volunteers with a healthy body mass index (BMI) who were found to be insulin-resistant had a higher risk, report researchers in the September 4th issue of the Journal of the American College of Cardiology.

Insulin resistance occurs when cells become desensitized to the body's key blood sugar-regulating hormone. Normally, insulin is secreted to clear glucose (sugar) from the blood and deposit into cells to use as energy. Obesity, however, can make the cells less responsive to the hormone, forcing the body to churn out more and more to keep blood glucose levels down.

Over time, elevated blood sugar levels can raise the risk of developing heart disease.

"A significant amount of the increased heart disease risk associated with obesity is unrelated to obesity per se, but is due to the fact that the heavier an individual, the more likely they are to be insulin resistant," Dr. Gerald M. Reaven, a study author, explained in an interview with Reuters Health.

Therefore, doctors should broaden their focus from obesity as an isolated risk factor for heart disease, to include insulin resistance. Weight loss can lower the risk of heart disease in those who are both overweight and insulin resistant but insulin-resistant patients who are normal weight should be encouraged to get more physical activity, Reaven said.

More than 300 study volunteers free of diabetes and hypertension underwent a regular glucose challenge test to measure insulin sensitivity. The test measures the amount of glucose (sugar) remaining in the blood after a person consumes a sugary drink or is infused with a glucose solution.

The volunteers were categorized as normal weight (BMI less than 25), overweight (BMI between 25 and 30), or obese (BMI over 30). BMI or body mass index is a measure of a person's weight in relation to their height and is considered a more accurate predictor of heart disease and type 2 diabetes, than weight alone.

As expected, the likelihood of insulin resistance rose in tandem with BMI. Insulin resistance and BMI were also independently related to a person's age, blood pressure, cholesterol levels, and other heart disease risk factors.

But about 25% of those who were insulin-resistant were normal weight--the same proportion of all insulin resistant individuals that was obese. Some obese volunteers were not insulin-resistant. Overall, BMI alone contributed just 22% to the risk of insulin resistance, report researchers.

"Obesity does not equal insulin resistance," Reaven told Reuters Health. The researchers estimate that 50% of the variation in insulin resistance is due to genetic factors, 22% to BMI and the remainder due to a sedentary lifestyle.

SOURCE: Journal of the American College of Cardiology 2002;40.

http://www.reutershealth.com/archiv...903elin010.html

Dr. Gerald M. Reaven is an Endocrinologist who has devoted his career to researching and publishing the effects of Syndrome X --- Insulin Resistance.

For a long time, many scientists and practitioners scoffed at the existence of Syndrome X, but Reaven's (and others) persistence have proven not only its existence, but its significance in health and disease.

Reaven has published a number of books relating to Insulin Resistance and disease. Please check out Overcoming Syndrome X: The Silent Killer That can Give You a Heart Attack for more information.

Doreen

Doreen T--

Very helpful. Thanks!

Sheldon