Sue Kimm, M.D., of the University of Pittsburgh School of Medicine, and colleagues found that by ages 16 or 17, 56 percent of black girls and 31 percent of white girls report they have no regular leisure-time physical activity. The study was published in the September 5 issue of The New England Journal of Medicine.
Kimm and colleagues studied 1,213 black girls and 1,166 white girls enrolled in the NHLBI Growth and Health Study from ages 9 or 10 to ages 18 or 19 years. A questionnaire measuring leisure-time physical activity was administered to the girls seven times during the study (years 1, 3, 5, and 7 to 10).
The scientists found an association between lower levels of parental education and activity decline in white girls of all ages and in older black girls (ages 13 to 17). Higher body mass index (a measure of body weight adjusted for height) predicted a decline in activity among both racial groups.
Pregnancy was associated with activity declines in black but not in white girls. According to Kimm, there may not have been an adequate number of pregnancies among white girls to detect a statistically significant effect on physical activity. Kimm noted that a similar situation may explain the race-specific results for smoking. Although cigarette smoking predicted a greater activity decline in white girls only, relatively few black girls smoked. Thus, there may not have been enough black smokers to detect an effect on physical activity.
Given the current epidemic of obesity, the researchers conclude that the "precipitous" drop in activity levels during adolescence "should sound an alarm" for action. They suggest that the risk factors identified in this study could help prioritize education resources and guide prevention efforts. Eva Obarzanek, Ph.D., research nutritionist, NHLBI, is available to comment on the study and the problem of obesity and low levels of physical activity in youth. To interview Dr. Obarzanek, call the NHLBI Communications Office at (301) 4926- 4236. To interview Dr. Kimm, call (412) 648 -1968.
Information about obesity, physical activity, and NHLBI's Hearts N' Parks program is available online at www.nhlbi.nih.gov. Hearts N' Parks is a national community-based program focused on reducing obesity and the risk of heart disease by encouraging all Americans to aim for a healthy weight, follow a heart-healthy eating plan, and engage in regular physical activity.
Journal
New England Journal of Medicine