'There is nothing wrong with a baby being heavy as an infant as long as he's regulating his own eating,' says one expert.

As obesity reaches epidemic proportions in the United States -- 30 percent of adults are obese and 65 percent are obese or overweight -- researchers are looking for keys to prevent it. Those efforts may need to begin in childhood, the researchers said.

"Levels of obesity are increasing in the population, and halting the rising prevalence of obesity is a public health priority," said study lead author Dr. Janis Baird, a research fellow at the MRC Epidemiology Resource Centre at the University of Southampton.

"It is not clear how early prevention can begin," she added.

Nurture, More Than Nature

To determine whether obesity may begin in infancy, Baird and her colleagues looked at 24 studies that found a relationship between infant size or growth during the first two years of life and obesity later in life.

They found that the heaviest infants and those who gained weight rapidly during the first and second year of life faced a nine-fold greater risk of obesity in childhood, adolescence and adulthood.

"These findings suggest that factors in infant growth are probably influencing the risk of later obesity," Baird said. "There are many factors that do influence infant growth. What's needed now are much more detailed studies to look at how infants grow and what the predictors of their growth are."

The study findings appear in the Oct. 14 online edition of the British Medical Journal.

One expert believes that nurture, more than nature, is responsible for the rise in obesity among children.

"If people take this too seriously, people may start calorie-restricting their infants, which is a bad thing," said Dr. Dennis Woo, chairman of the pediatrics department at Santa Monica-UCLA Medical Center, in California.

Learn from Infants?

According to Woo, children regulate their own calorie intake.

"A lot of kids eat what they want to eat, and they do a pretty good job of regulating their weight and height balance. There are some kids who grow rapidly in the first year, but then they go through a phase where they become picky as far as their eating goes," added Woo, who's also an assistant clinical professor of pediatrics at the University of California, Los Angeles David Geffen School of Medicine.

Woo advises parents to let infants eat what they want to eat and not force them to eat during the time they are picky about eating. "We are fighting the cultural belief that fat babies are healthy babies," Woo said. "So people like to fatten their kids up."

Many parents also believe fat babies are fine because they slim down when they are older, Woo said. "That doesn't always happen. People use that as a rationale for really stuffing their kids."

"There is nothing wrong with a baby being heavy as an infant as long as he's regulating his own eating," Woo said. "There will come a time when he will not be growing and he will cut down on his eating. Most of the time, those are the big babies who then slim down."

Woo believes healthy eating habits begin in infancy.

"We want to teach all kids healthy eating habits right from the very beginning," he said. "We need to shape how people look at eating. Because infants don't have the psychological cues that adults have, they respond to their biological needs. We could actually learn from infants about how to eat."

More information: The National Institutes of Health can tell you more about childhood obesity.