As the population ages, more people will be classified as “disabled” more quickly if health messages aren’t heeded, according to a large U.S. study.

Researchers from the University of Houston studied more than 20,000 people who participated in the Aerobics Center Longitudinal Study between 1974 and 2006.

They were examined several times during the study, which included a treadmill test and counselling on diet, exercise and other lifestyle factors.

Statistical models show­ed, not surprisingly, that heart and breathing fitness declined as people aged. And the decline speeds up after age 45.

Fitness levels eroded faster in men than in women. Researchers found that people can fend off these declines in fitness and keep health problems at bay by maintaining a healthy BMI, not smoking, and staying active.

“The U.S. population is aging and is becoming more obese and sedentary,” the authors wrote.

“These data indicate the need for physicians to recommend to their patients the necessity to maintain their weight, engage in regular aerobic exercise and abstain from smoking,” they concluded. The article was published in the Oct. 26 issue of Archives of Internal Medicine.

Obesity rates are higher in the U.S. than in Canada: about 30 per cent, compared to 23 per cent. A recent study found that obese workers take 10 times more sick days than normal-weight employees.