The proportion of American adolescents who exercise regularly, eat a healthy diet and are free of risk factors for future heart disease is "alarmingly low," says a major new survey of teen health. The comprehensive five-year assessment of teens' health status warns that the "disconcertingly high" rate of poor health habits among the nation's youth "may contribute to unacceptably high rates of adult-onset cardiovascular disease" as this cohort matures into adulthood.