Americans’ weight problems may start as early as toddlerhood, and don’t always fade with maturity, a new study shows.

The study looked at more than 1,000 American children and appears in the September issue of Pediatrics, the official journal of the American Academy of Pediatrics. Its take-home message: Don’t assume kids will outgrow their childhood chubbiness.

“Sixty percent of children who were overweight at any time in the preschool period, and 80 percent of the children who were overweight at any time during the elementary period were overweight at age 12 years,” write Philip Nader, MD, of the University of California, San Diego, and colleagues in the study.

Results were similar for boys and girls.

It may be better to address plumpness early on, “rather than delaying in hopes that overweight and the patterns that support it will resolve themselves in due course,” write the researchers.

Nader’s team studied children in 10 U.S. cities from age 2 to 12. The children were born in 1991, when America’s waistline had already started to expand.

The researchers tracked the kids’ BMI (body mass index, a measure based on height and weight). Overweight was defined as having a BMI in the top 15 percent for their age group.

The study found that those overweight at any time before age 12 -- even at the tender age of 2 -- were more likely to be overweight at 12.

About the Study

The kids’ height and weight were measured seven times -- at ages 2, 3, 4 1/2, 7, 9, 11, and 12.

Using the measurements, the researchers calculated the children’s BMI.

“The more times a child was overweight, the greater the odds of being overweight at age 12 years relative to a child who was never overweight,” Nader’s team writes.

The reverse was also true. Kids at the lower end of the BMI range for their age tended not to be overweight at age 12.

Other studies have shown similar results, though they may not have tracked kids’ BMI as closely, Nader’s team notes.

Parents Don't Realize Their Children are Overweight

Time to Step In?

“Any time a child reaches the 85th percentile for BMI may be an appropriate time for intervention,” Nader says, in a UC San Diego news release.

He offers some specific advice for parents.

“Parents should demand that the environment that their child is exposed to include healthy foods, less exposure to TV and sedentary activities, and safe, active places for physical activity, including neighborhood parks and quality physical education in schools,” Nader says.

Kids are growing and need good nutrition, so grown-up diets may not be appropriate. Concerned parents should consult the child’s doctor for guidance.

How to Help Your Child to Lose Weight

Findings in Focus

The study has some limitations. It doesn’t show what the kids ate, how active they were, whether they tried to lose weight, or whether their parents were overweight.

The findings don’t mean all overweight toddlers will become overweight tweens, or that lean children will stay slender.

In fact, the study shows that 40 percent of the kids ever overweight in preschool, and 20 percent of those ever overweight in elementary school, were not overweight at age 12.

Still, not being overweight “is a positive health goal for most individuals,” and, “efforts to reduce overweight need to begin in childhood,” write Nader and colleagues.

What is Obesity?

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Nader, P. Pediatrics, September 2006; vol 118: pp e594-e601. News release, University of California, San Diego. News release, National Institute of Child Health and Human Development, National Institutes of Health.