In a study of more than 500 people, experts found that 15-year-olds with high cholesterol levels can normalize those levels by their mid-30s, emphasizing the importance of targeting teens with health campaigns, the BBC reports. In the Australian study, participants had their levels of cholesterol and blood fats measured in 1985, when they were 9, 12 or 15, and then again between 2004 and 2006. Height, weight, waist circumference, skin-fold thickness, smoking habits and cardiorespiratory fitness were measured, too. Participants with high-risk cholesterol levels in their youth, those who stopped smoking or lost weight, became low-risk by the time they were adults. But those who upped their body weight or started smoking were more likely to maintain risk levels.