Obesity Is Found to Gain Its Hold in Child's Earliest Years

For many obese adults, the die was cast by the time they were 5 years old. A major new study of more than 7,000 children has found that a third of children who were overweight in kindergarten were obese by eighth grade. And almost every child who was very obese remained that way.

Some obese or overweight kindergartners lost their excess weight, and some children of normal weight got fat over the years. But every year, the chances that a child would slide into or out of being overweight or obese diminished. By age 11, there were few additional changes: Those who were obese or overweight stayed that way, and those whose weight was normal did not become fat.

“The main message is that obesity is established very early in life, and that it basically tracks through adolescence to adulthood,” said Ruth Loos, a professor of preventive medicine at the Icahn School of Medicine at Mount Sinai in New York, who was not involved in the study.

These results, surprising to many experts, arose from a rare study that tracked children’s body weight for years, from kindergarten through eighth grade. Experts say they may reshape approaches to combating the nation’s obesity epidemic, suggesting that efforts must start much earlier and focus more on the children at greatest risk.

The study involved 7,738 children from a nationally representative sample. Researchers measured the children’s height and weight seven times from kindergarten to eighth grade.

When the children entered kindergarten, 12.4 percent were obese — defined as having a body mass index at or above the 95th percentile — and 14.9 percent were overweight, with a B.M.I. at or above the 85th percentile. By eighth grade, 20.8 percent were obese and 17 percent were overweight. Half of the obese kindergartners were obese when they were in eighth grade, and nearly three-quarters of the very obese kindergartners were obese in eighth grade. The risk that fat kindergartners would be obese in eighth grade was four to five times that of their thinner classmates, the study found.

Race, ethnicity and family income mattered in younger children, but by the time the overweight children were 5 years old, those factors no longer affected their risk of being fat in later years.

Some obesity researchers said the new study following kindergartners over the years also hinted at another factor: the powerful influence of genetics on obesity, something that can be a challenge to overcome

And, he said, a number of randomized studies involving young children have shown that it is possible to stop or reverse excess weight gain. One, for example, had some fat children ages 4 to 7 reduce their television and computer viewing time, and had others keep theirs the same. Children in the intervention group — especially those from poorer families — consumed fewer calories, and their body mass index fell.