CHICAGO (AP) — The earlier children lose their baby fat and reach the leanest point of their growing-up years, the more likely they will become obese, suggests a study released Monday.
The finding held true regardless of whether children’s parents were overweight, which is already known to be a strong indicator of a child’s future size, researchers reported in the March issue of Pediatrics.
The new finding suggests something biologically important may be happening at about age 6, researchers said.
Meanwhile, federal researchers reported that the number of overweight children continued to increase through 1994.
By then, about 4.5 million children, or 11 percent of youngsters ages 6 to 17, were markedly overweight. That compares with about 5.5 percent in 1980 and about 4 percent in 1963-65.
In the first report, researchers found that children who lose their baby fat and reach their thinnest point of childhood before age 5 are more than twice as likely to be obese adults as children who reach the thinnest point after age 5.
All children grow leaner after the first year of life until age 5 or 6, when they become fatter again, noted researchers led by Dr. Robert D. Whitaker, a pediatrician at Children’s Hospital Medical Center in Cincinnati.
The age of greatest leanness is called “adiposity rebound,” and researchers compared differing ages at which it occurred among 390 subjects who were tracked until they were 21 to 29 years old.
The children were divided into three groups according to when they reached adiposity rebound. Those who did before they were 4.8 years old were compared with those who did between ages 4.8 and 6.2 years and those who reached the stage after age 6.2 years.
“We don’t know for sure, but … it would be reasonable to expect that’s a critical developmental period, just as it is for language development or capacity for listening to music or any of a number of things,” Whitaker said in a telephone interview.
The finding has no immediate practical implication, Whitaker said. But future research could reveal strategies to help early rebounders avoid obesity, he said.
A researcher not associated with the study agreed.
“In terms of understanding causes and possibly understanding intervention points, this is potentially very important,” said Aviva Must, a childhood obesity researcher at New England Medical Center in Boston.
As for the rise in overweight children, lack of exercise is suspected as a main cause.
In young children, for example, there was no significant rise in calorie consumption corresponding to the rise in overweight, said epidemiologist Richard P. Troiano of the National Cancer Institute, the lead author of the report.
“There needs to be a healthy diet, but rather than trying to figure out what foods to take away and restrict, I find it a more positive message to encourage more physical activity,” he said.
His report was contained in a special supplement on childhood obesity also published by the American Academy of Pediatrics and released Monday.
Troiano’s report classified children as overweight if they had a greater body-mass index — which combines weight and height — than 95 percent of children in their age groups.