NEW YORK - The heavier a woman is at the age of 18, the greater is her risk of dying prematurely, according to a large study published Monday.

Harvard researchers found that of the more than 100,000 U.S. women, who were overweight or obese at age 18, faced a higher risk of early death from heart disease, cancer, suicide and other causes 12 years later.

Women who were overweight at 18 were 66 percent more likely to die prematurely than those who were thin, while obesity at age 18 nearly tripled the risk of dying in young by middle-age.

Researchers from the Harvard School of Public Health in Boston report the findings in the Annals of Internal Medicine.

Although overweight and obese teens are likely to remain so as adults, adulthood weight did not completely explain the link between teenage weight and premature death, said principal study author Dr. Frank B. Hu.

This suggests that childhood obesity itself has lasting health effects, he told Reuters Health, and it's not clear whether weight loss later in life erases the damage.

"Losing weight can certainly reduce the risks," Hu said, "but whether it completely eliminates them is unclear."

He said the findings underscore the importance of preventing excessive weight gain in the first place. "This is further evidence that childhood obesity is a major public health problem," Hu said.

The findings come from the long-running Nurses' Health Study II, which began following 116,671 female nurses in 1989, when the women were between 24 and 44 years of age.

Participants completed detailed health questionnaires at the study's start and at regular intervals thereafter. The first survey asked them to estimate their weight at age 18.

Over the next 12 years, 710 women died, with an increase in risk climbing in tandem with weight at age 18. Compared with women who were normal-weight at 18, those who were overweight were more than three times as likely to die prematurely of heart disease or stroke and 40 percent more likely to die of cancer.

They were also about twice as likely to commit suicide.

These weight-related risks remained when the researchers factored in lifestyle habits like smoking, exercise and alcohol use.

It's possible, according to Hu's team, that excess body fat in adolescence has specific and lasting effects on the metabolic or cardiovascular systems that contribute to premature death.

Whatever the reason for the link, the researchers say, the findings once again highlight the need for obesity prevention early in life. Health consequences often do not take years to emerge, Hu noted, as heavy children can develop serious problems like type 2 diabetes and high blood pressure.