We all know that carrying around extra weight increases the risk of heart disease, but the length of time a person has been toting that weight appears to be a factor as well. Children and adolescents who are obese — about 18% of the adolescent population right now — are in far more danger of developing heart disease than anyone ever considered.

Heart disease is the leading cause of death among men and women in the US, accounting for 600,000 deaths per year. Coronary heart disease, the most common form, develops when the arteries that supply the heart with blood, oxygen, and nutrients become damaged or diseased.

The usual cause is plaque, a combination of calcium, fat, cholesterol, and other substances. The accumulation of plaque, called atherosclerosis, is often the precursor to a heart attack or stroke.

Among those who were obese for over 20 years, 38 percent had calcification in the coronary arteries compared to 25 percent of those who never were obese. Higher rates of type 2 diabetes were also present in those who had been obese the longest.

Twenty-five years ago, at what we now know was the start of the obesity epidemic, researchers enrolled nearly 3,300 white and African-American adults between the ages of 18 and 30 in a study designed to look at the development of coronary artery disease in young adults. The participants were examined by a physician every two to five years and had CT scans at 15, 20, and 25 years into the study to detect calcification (hardening) in the coronary arteries.

The information collected on each participant included their body mass index, whether they smoked or not, cholesterol, blood pressure, physical activity level, and whether or not they developed type 2 diabetes.

How long a person had been overweight or obese was linked to accelerated atherosclerosis. Coronary artery calcification was discovered in nearly 28 percent of the participants. The length of time each person was obese, based on their physical exams over the years, correlated with the presence and the extent of blockage in the arteries. Among those who were obese for over 20 years, 38 percent had calcification in the coronary arteries compared to 25 percent of those who never were obese.

The risk of developing plaque increased by two to four percent for every year the young adults were obese, independent of all other factors measured on the participants. Those who had been obese the longest and who had abdominal obesity had increased odds of developing high blood pressure and elevated cholesterol and were more likely to be on medications to control those conditions. Higher rates of type 2 diabetes were also present in those who had been obese the longest.

Overall, the study implies that the earlier one becomes obese, the more likely it is that major heart problems will develop by middle age. Given the fact that over the past thirty years the rate of obesity has doubled among children and tripled among adolescents, more of today’s children and teens are likely to experience coronary events as they reach mid-life.

People are becoming obese at younger ages than previous generations. The results of this study make clear that this will likely have significant implications on the incidence of heart disease in the future and underscore the need for programs aimed at tackling obesity among our children and teens.

The study is published in the Journal of the American Medical Association.