Baby fat.

Baby fat

Overfeeding baby female baboons makes the primates fatter-than-normal adults, according to a study by Douglas S. Lewis and his colleagues at the Southwest Foundation for Biomedical Research in San Antonio, Tex. The association may apply to humans, Lewis says, but he is quick to caution that no benefits of underfeeding were seen and that parents should not underfeed their babies in order to ensure a svelte adulthood for them.

Lewis and his colleagues gave 40 percent more formula thanusual to 12 baby baboons, gave 30 percent less than normal to another 8 and gave 12 enough calories to equal what they would have gotten from breast feeding. They kept the animals on the diets from birth to 4 months of age, then allowed them to eat as much as they wanted. Their weight and amount of fat were monitored for 5 years.

While the overfed baboons were initially fatter, by 1 year ofage there were no differences. But the effect in 5-year-old female baboons--physiologically the equivalent of 15-year-old humans--was distinct. The percentage of weight due to body fat was 28 percent in the females overfed as infants, compared with 7 percent in both the normal-fed and underfed. No such difference was seen in the males -- possibly, Lewis suggests, because while females baboons at age 5 have just completed puberty, males are in the midst of the process. After puberty, he says, things may even out.

While some researchers maintain that obesity is caused byexcess fat cells, the current study suggess that this may not be the case, Lewis says. The difference here, he says, was due to an enlargement of the fat cells, not an increase in their number.

The results indicate that infant overfeeding is a potentialfactor in adult obesity. But in humans, he says, "The great majority of obese infants do not become obese adults." He suspects adult obesity may be a two-step process. Somehow overfeeding endows an enhanced capability of storing fat, and then factors such as diet or genetics kick in during adulthood.

In any case, he emphasizes, parents concerned about whattheir children will look like as adults shouldn't deny them food as youngters. "There's no evidence that underfeeding keeps the animal leaner than a normal infant," he says.