The US Centers for Disease Control and Prevention says that one in five American teens has unhealthy cholesterol levels. Data collected between 1999 and 2006 show that the heavier teens are, the more likely they are to have high cholesterol, but even 14 percent of normal-weight teens involved in the study had problematic cholesterol levels. This trend is particularly worrisome because unhealthy cholesterol levels are a major factor in heart disease. Experts recommend that doctors screen youth who have risk factors for high cholesterol and instruct them on lifestyle changes that can improve their health.