Physical Activity and the Metabolic Syndrome

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Physical activity energy expenditure predicts progression toward the metabolic syndrome independently of aerobic fitness in middle-aged healthy Caucasians, by U. Ekelund and colleagues. Diabetes Care 28:1195-1200, 2005.

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

The metabolic syndrome is a group of health risks that can lead to type 2 diabetes. These risks include having high blood pressure, being overweight or obese, and having high cholesterol (a waxy, fat-like substance that builds up in the blood vessels) and triglycerides (or fats in the blood vessels). Past studies have shown that physical activity and aerobic fitness can help protect against getting the health risks that can lead to type 2 diabetes.

Physical activity doesn't necessarily mean an exercise program or working out. It refers to daily routines that boost activity levels, like walking the dog or taking the stairs instead of the elevator. Aerobic fitness refers to exercises that raise your heart rate and keep it raised for a long time. If you are aerobically fit, then your muscles get more oxygen, allowing them to work longer and better.

The problem with the past studies is that it was hard to measure how physical activity really affects someone’s chances of avoiding the health risks that can lead to type 2 diabetes. Most of these studies relied on the subjects’ own reports of how active they were. That made it hard to measure how physical activity, regardless of one’s level of aerobic fitness, really affected a person’s chances of getting the metabolic syndrome.

Why did the researchers do this particular study?

To see how physical activity, aerobic fitness, and being overweight or obese affect the chances of getting the health risks that can lead to type 2 diabetes.

Who was studied?

A total of 605 healthy middle-aged adults (249 were men) who took part in the Medical Research Council Ely Study. None of the subjects had the metabolic syndrome when the study started.

How was the study done?

To find out each subject's fitness level at the start of the study, the researchers measured the subjects' heart rates while they rode an exercise bicycle. Their heart rate while riding the bicycle was compared with their heart rate when they were resting to measure how much energy they burned while exercising. The people in the study also had to wear a heart rate monitor for 4 days. Aerobic fitness was found by measuring the oxygen the body takes in when their heart rate was highest. The study lasted for over 5 years.

What did the researchers find?

The researchers found that higher levels of physical activity lower a person's chances of getting the health risks that can lead to type 2 diabetes, regardless of the person's level of aerobic fitness or weight.

What were the limitations of the study?

The authors didn't use the best way to measure aerobic fitness, but their method was still very reliable and probably didn't affect the results of the study.

What are the implications of the study?

Efforts to prevent the metabolic syndrome should start with physical activity. Even small increases in levels of physical activity can help people avoid the health risks that can lead to type 2 diabetes.

FOR MORE INFORMATION

The Metabolic Syndrome

The “I Hate to Exercise Book” for People with Diabetes , by Charlotte Hayes (Alexandria, Va., ADA, 2000)

Physical activity/exercise and type 2 diabetes, by R.J. Sigal and colleagues. Diabetes Care 27:2518–2539, 2004

Metabolic syndrome risk factors revisited, by P. Connor. DOC News, June 2005, p. 6.