The Centers for Disease Control and Prevention (CDC) recommends that adults exercise moderately (i.e., walking briskly, mowing the lawn, swimming, bicycling) for a minimum of 30 minutes, five days a week. Unfortunately, more than 60% of American adults don’t achieve this recommendation, and a quarter of them aren’t active at all.

There is a well-established link between physical fitness and cardiovascular disease (CVD) risk. People who are fit are less likely to have high blood pressure , diabetes , and high cholesterol , which are all risk factors for CVD. But, since exercise helps control weight—which affects your risk of CVD—some researchers question whether it’s fitness or weight control that is responsible for the cardiovascular benefits.

A new study in the December 17, 2003 issue of the Journal of the American Medical Association found that people who were more fit as young adults (ages 18-30) were less likely to develop risk factors for CVD during the 15-year study period.

About the Study

This study used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, which was designed to investigate the development of CVD risk factors in the 18–30 age group.

Before the study began, the 4,487 men and women participants underwent a fitness assessment, which involved a treadmill test in which they exercised as long as they could, up to nine two-minute stages of increasing difficulty. After seven years, a subset of 2,478 of the participants repeated this test.

Based on the treadmill test duration, the researchers categorized the participants as having a low, moderate, or high fitness level.

The researchers followed the participants for 15 years and tested them for the following CVD risk factors before the study began, and at years 2, 5, 10, and 15:

  • Diabetes
  • High blood pressure
  • High cholesterol
  • Metabolic syndrome (a cluster of three of the following heart disease risk factors: glucose intolerance, elevated blood pressure, abdominal obesity, elevated triglycerides , and/or low HDL cholesterol)

The researchers calculated how fitness affected the likelihood of developing these risk factors.

The Findings

Low and moderate fitness levels increased the risk of developing diabetes, high blood pressure, and the metabolic syndrome by 3–6 fold. Even after adjusting for the participants’ age, race, sex, smoking status, and family history of high blood pressure, diabetes, or heart attack, these risks remained double among participants with a low fitness level, compared with those with a high fitness level. Only the risk of developing high cholesterol was not significantly affected by fitness level.

On average, duration on the treadmill test decreased by an average of one minute over the seven years between tests. People whose fitness level improved (increased duration) were 50% less likely to develop diabetes and the metabolic syndrome, regardless of their age, sex, race, smoking status, and family history of diabetes. After adjusting for body mass index (BMI, a measure of weight in relation to height) and weight change, however, improved fitness at seven years did not significantly contribute to diabetes and metabolic syndrome risk.

Although these results are intriguing, they are limited because fitness was assessed solely by treadmill test duration. The treadmill test is highly correlated with the “gold standard” of fitness testing—maximum oxygen consumption per unit time (VO2)—but it is not a perfect measure of fitness.

How Does This Affect You?

These findings suggest that your fitness level as a young adult can help predict whether you will develop CVD risk factors as you approach middle age. Even better, improvements in your fitness level may reduce your risk for developing diabetes and metabolic syndrome.

Although this study was conducted in young adults, other research strongly indicates that maintaining or enhancing your physically fitness is quite likely to improve your health and quality of life at any age. No one is too old or infirm to enjoy the benefits of regular exercise. As researchers uncover more and more benefits of physical activity, it’s hard to find a legitimate excuse to keep still.