(CBS News) It's never too late to start exercising. A new study shows that people who are fit in their 30s through 50s are more likely to avoid chronic illness in their later years.
Fitness has been shown to boost health and extend lifespan, but this research shows that it may also lower risk of getting lung cancer, colon cancer, heart problems, obstructive pulmonary conditions, stroke, kidney disease, diabetes and Alzheimer's disease.
"We've determined that being fit is not just delaying the inevitable, but it is actually lowering the onset of chronic disease in the final years of life," senior author Dr. Jarett Berry, assistant professor of internal medicine at UT Southwestern Medical Center in Dallas, Texas, said in the press release.
According to the Centers of Disease Control and Prevention, adults between 18 and 65 should get at least two and a half hours of moderate-intensity aerobic activity every week. It is also acceptable to partake in one hour and 15 minutes of vigorous -intensity aerobic activity weekly. At least twice a week, adults should partake in muscle-strengthening activities.
For the study, which was published online in August 2012 in the Archives of Internal Medicine, researchers looked 18,670 participants in the Cooper Center Longitudinal Study, which contained records of more than 250,000 patients over 40 years. The compared the data with the participant's Medicare claims during the ages of 70 to 85.
Patients who were able to increase their fitness levels by 20 percent in their midlife years were able to decrease their chance of developing chronic illness by 20 percent in their later years. By the time the subjects reached the age of 50, the part of the group in the lowest 20 percent of the fitness scale had almost twice as many chronic illnesses than the people in the highest 20 percent. The people with the highest fitness levels at midlife had 34 percent more time with one or no chronic illness than those who were the least fit.
Fitter people were also more likely to live their last five years with fewer chronic diseases. The results were similar in both men and women.
"What sets this study apart is that it focuses on the relationship between midlife fitness and quality of life in later years. Fitter individuals aged well with fewer chronic illnesses to impact their quality of life," first author Dr. Benjamin Willis of The Cooper Institute said in the press release.
However, the study showed that people who were more fit were no less likely to die earlier than those who were least fit. The fittest people were more likely to live healthily until they died suddenly or suffered from a short illness, while the least fit people were more likely to suffer from an illness for quite some time as their health slowly went downhill.
In an accompanying commentary published in the same journal, Dr. Diane Bild, associate director of the Prevention and Population Sciences Program at the National Heart Lung and Blood Institute, said this new research implies that fitness can help people live healthier years. She interpreted the results with caution, however, since 98 percent of the participants in the study were white. She also pointed out that genetics may play a bigger part in the results - meaning exercise may not lead to fitness in all cases.
"Because genetics likely plays a role in longevity and certainly plays a role in disease avoidance, if some of the same genes are involved in the longevity and fitness, they may serve as major confounders in the attractive interpretation that exercise leads to fitness, which leads to healthy aging," she said.