A rare study that tracked thousands of children through adulthood found the heaviest youngsters were more than twice as likely as the thinnest to die prematurely, before age 55, of illness or a self-inflicted injury.

Youngsters with a condition called pre-diabetes were at almost double the risk of dying before 55, and those with high blood pressure were at some increased risk. But obesity was the factor most closely associated with an early death, researchers said.

The study, published Thursday in The New England Journal of Medicine, analyzed data gathered from Pima and Tohono O'odham Indians, whose rates of obesity and Type 2 diabetes soared decades before weight problems became widespread among other Americans. It is one of the largest studies to have tracked children for several decades after detailed information on weight and risk factors like high cholesterol were gathered.

“;This suggests,”; said Helen C. Looker, senior author of the paper, “;that obesity in children, even prepubescent children, may have very serious long-term health effects through midlife—that there is something serious being set in motion by obesity at early ages.”; Looker added, “;We all expect to get beyond 55 these days.”;

Nearly one in three American children is now considered to be either overweight or obese, and this week, the first lady, Michelle Obama, kicked off a campaign intended to end childhood obesity.

The new study analyzed data gathered about 4,857 non-diabetic American Indian children born between 1945 and 1984, when the children were 11 years old on average, and assessed the extent to which body mass index, glucose tolerance, blood pressure and total cholesterol levels predicted premature death.

By 2003, 559 participants had died, including 166 who died of causes other than accidents and homicides, like cardiovascular disease, infections, cancer, diabetes, alcohol poisoning or drug overdose and a large number who died of alcoholic liver disease, which the study's authors suggested might be exacerbated by diabetes.

Adults who had the highest body mass index scores as children were 2.3 times as likely to have died early as those with the lowest scores, and those with the highest glucose levels were 73 percent as likely to have died prematurely.

“;This really points a finger at impaired glucose tolerance, or pre-diabetes, in ways we have not seen before,”; said Edward W. Gregg, who is with the diabetes branch of the U.S. Centers for Disease Control and Prevention, and wrote an editorial accompanying the article. “;We've been aware that pre-diabetes in adults is related to a lot of adverse outcomes, but the relationship in youth has not been as clear. There are not as many long-term studies to document a risk factor like pre-diabetes in youth all the way to adult outcomes.”;

The study found that high blood pressure in childhood was only a weak predictor of early death and high cholesterol was not associated with premature death, but experts suggested those factors were easier to control with medication.

And though the American Indian community is not representative of the nation's population as a whole, Gregg said its experience was instructive because, “;they've tended to be just a decade or two ahead of the rest of the U.S. population”; in obesity.

“;The message here is that if you take your kid to the doctor and the doctor says, 'Well, their blood pressure is OK, their cholesterol is OK and their sugar's OK,' the kid who's obese still warrants our attention,”; said Dr. Peter F. Belamarich, chief of specialty medicine at the Children's Hospital at Montefiore in New York.