TUESDAY, Sept. 5 (HealthDay News) -- So-called "baby fat" in young children could be a predictor of weight problems much later on, researchers say.

In fact, preschool-age children who are overweight before age 5 are five times more likely to be overweight at age 12 than those who were not overweight before age 5, a new study finds.

"The problem of obesity and overweight in kids is they don't outgrow it," said lead author Dr. Philip R. Nader, professor emeritus of pediatrics at the University of California, San Diego. "A lot of people think that baby fat will go away and not to be too concerned, but this isn't the case," he said.

In the study, the researchers collected data on over 1,000 children born in 1991. "These kids grew up during the period when the obesity epidemic began," Nader said.

Nader's team measured the height and weight of the children at seven points in their development: three times in the preschool age (at two, three, and four-and-a-half years of age); three times in the school-age period (seven, nine and 11 years of age); and finally at age 12.

They found that the more times a child was overweight during preschool and elementary school, the greater the likelihood that he or she would be overweight at the age of 12.

Compared to children who never measured as overweight, a school-age child who was overweight at one measurement had a 25-fold greater chance of being overweight at age 12, the researchers found. Those odds rose to 159-fold if the child was overweight at two measurements, 374-fold if they were overweight at three or more measurements.

Overall, 60 percent of children who were overweight at any time during the preschool years, and 80 percent of children who were overweight at any time during elementary school, were still overweight at age 12.

"Something needs to be done with the environment that's helping all these kids become overweight," Nader said. "As a society, we need to do something more to insure that kids have a safe place to play, get plenty of exercise and have a healthy diet," he said.

One expert believes clinicians and parents must work together to recognize and fight the childhood obesity epidemic.

"We have long known that childhood obesity predicts adult obesity," said Dr. David L. Katz, an associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine. "These findings are of great concern, given the well-documented and relentless increases in childhood obesity rates," he added.

There is a good reason why excessive weight gain early in life establishes a lifelong propensity to obesity, Katz said. "In early childhood and at puberty, we are adept at turning excess calories into new fat cells," he said. Because fat cells shrink but do not disappear, "we then tend to be stuck with an increased number of fat cells for life," Katz said.

"Nearly all children are vulnerable to epidemic obesity and the risk of diabetes," Katz said, so parents must be vigilant and make sure kids get healthy diets and plenty of exercise. "We must do more than address these threats in the clinical setting," he said.

More information

There's more only helping kids eat right at the U.S. National Institutes of Health.