What you feed a newborn baby during the first week of life could be critical in deciding whether that baby grows up to be obese, U.S. researchers said on Monday.

They found that formula-fed babies who gained weight rapidly during their first week of life were significantly more likely to be overweight decades later.

"It suggests that there may be a critical period in that first week during which the body's physiology may be programed to develop chronic disease throughout life," said Dr. Nicolas Stettler, a pediatric nutrition specialist at The Children's Hospital of Philadelphia.

"Our findings also point toward new potential targets for preventing obesity," he added. "If these results are confirmed by other studies, they may lead to interventions in newborns to help prevent long-term development of obesity."

Stettler's team studied 653 white adults aged 20 to 32.

Writing in the American Heart Association journal

Circulation, they said each additional 100 grams (3.5 ounces) of weight gained during the first eight days of life increased a baby's risk of becoming an overweight adult by about 10 percent.

The study also helps reinforce recommendations that mothers breast-feed their babies.

"For a variety of health reasons, the American Association of Pediatrics recommends exclusive breast-feeding during a baby's first six months of life," Stettler said. Breast-fed babies are less likely to be overweight.

In a special issue on obesity, the Heart Association said childhood obesity is such a critical public health problem that it could reverse the gains made over the last 50 years in reducing heart disease and death.

An estimated 16 percent of U.S. children are overweight and carry a significant risk of developing heart disease and diabetes while young adults.

"Only 64 percent of mothers initiate breast feeding, and only 29 percent of babies are still being breast fed when they are six months of age. Rates of initiation and duration are even lower among African-American women," said Dr. Stephen Daniels of Cincinnati Children's Hospital Medical Center.

The Heart Association published a statement calling for a multi-pronged approach to preventing childhood obesity involving families, the health care system, private insurers, government agencies, schools and the food and entertainment industries.

"If you think about all the environmental factors that have contributed to excess weight gain, then prevention has to take an across-the-board approach that doesn't just happen in the physician's office," Daniels said.

All children should have weight, height and body mass index -- used to calculate obesity -- tracked each year, the Heart Association recommended.