Study included 1,000 Kaiser members from Oakland, followed subjects over 15 years
Wednesday, December 17, 2003 – People who failed a treadmill fitness test in their 20s had twice the risk of developing high blood pressure, diabetes and other cardiovascular problems later in life than their fit peers, according to a study of young adults from Oakland published Wednesday.
“At a time when obesity often means eating less, this highlights the importance of fitness,” said Dr. Stephen Sydney, associate director of Kaiser Permanente’s research division in Oakland and principal investigator of the study.
The 15-year study involved 4,400 black and white men and women from Oakland, Chicago, Birmingham, Ala., and Minneapolis. Nearly 1,000 Kaiser members from Oakland participated. The findings were published in this week’s Journal of the American Medical Association.
Fitness was based on how long participants could jog or walk on a treadmill without becoming short of breath, with heart rates measured before and after the test. The highly fit could jog or walk briskly for 20 to 30 minutes without becoming short of breath.
Participants, who were age 18 to 30 when the study began, first were tested in 1985 and 1986; some were tested seven years later, and again 15 years after the initial treadmill run, in 2000 and 2001. Those with low or moderate fitness results in 1985 were twice as likely as the highly fit to develop diabetes, hypertension and metabolic syndrome — a condition that includes high blood pressure, blood sugar and cholesterol and a large abdomen.
The findings were adjusted for age, race, gender, smoking and family history of diabetes and hypertension.
About 60 percent of women and 50 percent of men had low or moderate fitness levels. The average weight gain over 15 years was 28 pounds.
Numerous studies have connected obesity and cardiovascular diseases — a big killer in people over age 45.
This study, however, indicates that body mass and weight maintenance can only in part account for the development of hypertension and diabetes.
“Just being thin will not protect you,” Sydney said. “It’s also very important to exercise.” But fitness won’t protect those who become obese in childhood or adolescence from developing diabetes or metabolic syndrome, the authors found.
“This emphasizes even more the importance of preventing obesity,” Sydney said. “By and large, when people become obese they don’t become thin again.”
The authors suggested that the reason physical fitness protects many people from these life-threatening diseases is that the physically fit maintain a better caloric balance.
Fitness also promotes healthy insulin function, lower heart rates and improved nervous system — all which decrease the risk of developing diabetes and high blood pressure, apart from a person’s body mass.
The authors calculated that even if the association between cardiovascular disease and fitness is casual, if all the unfit participants had been fit, they would have seen 21 to 28 percent fewer cases of hypertension, diabetes and metabolic syndrome.
Sydney said the researchers just received further funding to continue the study, and he plans to do a 20-year check-in with Oakland participants in 2005.
Physical activity doesn’t have to be extreme to get benefits, said Cheryl Nelson, project officer at the National Health, Lung and Blood Institute, which funded the research.
“Americans don’t have to run marathons to improve their physical fitness,” Nelson said.
“They should try to engage in at least 30 minutes of a moderate-intensity physical activity, such as brisk walking on most, if not all days of the week.”