Obesity factors more complex than thought

Researchers and clinicians are taking a closer look at metabolic syndrome as an indicator of heightened risk for obese patients.

By Susan J. Landers — Posted Jan. 17, 2005

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Washington -- It's time for a little fine-tuning when it comes to assessing the cardiovascular risk posed by excess pounds, according to new findings that could enable physicians to better identify those overweight patients at imminent peril.

A determination of body mass index might not be the only number that counts anymore. Where the fat is stored, an individual's fitness level, blood markers for inflammation and the presence of metabolic syndrome also should be considered.

"Everyone who is obese does not seem to be at the same risk for cardiovascular disease," said Barbara Nicklas, PhD, associate professor in gerontology and geriatric medicine at Wake Forest University School of Medicine in Winston-Salem, N.C.

Dr. Nicklas was the principal investigator in a recent study that identified visceral fat as a prominent risk factor for postmenopausal women. The presence of fat surrounding internal organs also was the main determinant of who had metabolic syndrome, a condition that is believed to set the stage for future problems.

With recent figures showing that 65% of U.S. adults are overweight, physicians are sharpening their skills at counseling their patients to lose weight and become more physically active to reduce their risk of cardiovascular disease as well as diabetes and arthritis.

"The numbers out there are unbelievable," said Philip Ades, MD, professor of medicine at the University of Vermont College of Medicine. "When six of 10 patients are overweight and you are dealing with the medical issues, how could a doctor be in practice and not address this?"

Dr. Ades finds it helpful to divide his obese and overweight patients into those who are at high risk for cardiovascular disease and those at low risk.

Fitness levels recently have been found to make a difference. "So if you are overweight but very fit, you seem to be at much lower risk," he said. But very few people are in this category. "How many people around you are overweight but are really out there exercising five times a week?"

Metabolic syndrome, a collection of five indicators, is probably a much more telling measure of risk. Patients who have three of the five -- waist circumference of over 40 inches for men and 35 inches for women, high triglycerides, low HDL cholesterol, hypertension or high glucose levels -- are clearly more at risk than are other overweight patients, Dr. Ades said.

While physicians have taken note of this group of risk factors for years and have given it several different names, including syndrome X, evidence is building that more patients than ever are affected. As many as one in four American adults and 40% of adults 40 or older have metabolic syndrome, an increase of 61% over the last decade, the Mayo Clinic says.

Another indicator that divides people into a high- or low-risk group is the answer to this question: "Do they have high markers of inflammation as indicated by C-reactive protein levels," Dr. Ades said.

But rather than calculating all of the factors, physicians usually use BMI because it's a simple measure of excessive body fat, said Michele Bachhuber, MD, medical director of ProActive Health at Marshfield (Wis.) Clinic. "But it does have its limitations."

It's important to understand that where the fat is deposited can create a more dangerous situation, she said. Fat in the abdominal area is associated with increased risk for heart disease and strokes, and, because it's also one of the criteria for metabolic syndrome, "we need to start paying more attention to it," Dr. Bachhuber said.

Other factors

Another problem with relying too heavily on BMI alone is that even thinner people can have enough risk factors to be at risk for cardiovascular disease. A CT scan might be the only, albeit costly, way to detect the intra-abdominal fat in that group.

In her study, Dr. Nicklas and colleagues looked at not only whether fat was carried on the hips or in the abdomen but also whether it was stored between the skin and abdominal muscle wall or as visceral fat beneath the muscles and wrapped around the internal organs.

"We found that where the body fat is stored was the main determinant of who had metabolic syndrome," Dr. Nicklas said. "There have been a number of studies that indicate that visceral fat is worse, because it surrounds vital organs and may lead to more fat metabolism by the liver."

Dr. Nicklas' study was published in the November 2004 issue of the Journal of Clinical Endocrinology and Metabolism.

After becoming aware of a patient's excessive risk, physicians can be more persistent in counseling them to become more physically active and to control their blood pressure, blood sugars and cholesterol levels, said Dr. Bachhuber, who also chairs the Wisconsin Medical Society's obesity task force.

"It's important to emphasize the importance of physical activity to avoid those situations where someone looks physically fit but may still have excessive fat," she said.

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Diagnosing clues

The National Cholesterol Education Program has established a few indicators for metabolic syndrome. The syndrome can be diagnosed if three or more of the following traits are present:

  • Abdominal obesity, measured as a waist circumference of greater than 35 inches for women and 40 inches for men
  • Triglyceride levels of 150 mg/dL or higher
  • Blood pressure of 130/85 mmHg or higher
  • A fasting blood sugar level of 110 mg/dL or higher
  • A level of HDL cholesterol lower than 50 mg/dL for women and 40 mg/dL for men

Source: Mayo Clinic

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External links

The AMA's primer for physicians on treating adult obesity (link)

Mayo Clinic on metabolic syndrome (link)

Centers for Disease Control and Prevention on overweight and obesity (link)

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