Fitness, Metabolic Syndrome, Obesity, and Death

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Katzmarzyk PT, Church TS, Janssen I, et al.: Metabolic syndrome, obesity, and mortality: Impact of cardiorespiratory fitness. Diabetes Care 28:391-397, 2005.

What is the problem and what is known about it so far?

Metabolic syndrome is also known as "insulin resistance syndrome" or "syndrome X." It happens when someone has several disorders at the same time, such as obesity, high blood pressure, and high cholesterol. This affects how the body burns calories and uses insulin (which helps the body use or store glucose from food).

At least one in five overweight people has metabolic syndrome. They are at a higher risk of type 2 diabetes, heart disease, and early death. Doctors advise these patients to diet and exercise.

Researchers wanted to study the risk of death from metabolic syndrome, heart disease and other causes. They wanted to compare people who were normal weight, overweight, and obese. They also wanted to find out if a person's fitness affects the risk of death.

Who was studied?

Researchers studied more than 19,000 men from the Aerobics Center Longitudinal Study (ACLS). Their average age was 41. In total, 39% were normal weight, 47% were overweight, and 14% were obese. Most of the men in the study were college graduates and most were white.

How was the study done?

This study was based on information from the ACLS between 1979 and 1995. Researchers noted if the men had metabolic syndrome, their weight (normal weight, overweight, or obese), and their fitness. The ACLS got this information from questionnaires, physical exams, blood pressure measurements, and fitness tests. Information also came from the men’s electrocardiograms (also known as ECGs or EKGs, which measure heart rate and rhythm and show any damage or injury to the heart).

What did the researchers find?

The researchers found that the more the person weighed, the greater the chance of having metabolic syndrome. Smoking and heavy alcohol use also were linked with having metabolic syndrome.

Men with metabolic syndrome were more likely to die than those who did not have metabolic syndrome—no matter how much they weighed.

Obese men were more likely to die early than overweight and normal-weight men—whether they had metabolic syndrome or not.

Researchers also found that overweight and obese men were less likely to die early if they were physically fit. Men who exercised were less likely to die from heart disease.

What were the limitations of the study?

The people in the study were all men, mostly white, educated and middle and upper class. Because of this, the results may not apply to all other men.

What are the implications of the study?

People should try to be physically fit, even if they have a weight problem or metabolic syndrome. An active lifestyle can help person people live a longer life.

FOR MORE INFORMATION

The metabolic syndrome. http://www.diabetes.org/weightloss-and-exercise/weightloss/metabolicsyndrome.jsp.

Isomaa B, et al.: Cardiovascular morbidity and mortality associated with the metabolic syndrome. Diabetes Care 24:683–689, 2001.