Kids who were fed on formula for the first few months of life gained just as much weight up to age 10 as those who were exclusively breastfed, according to new research from Germany.

It has been unclear just what effect breastfeeding, compared to formula feeding, has on weight as an infant and later in life. The findings ease some early fears about stunted growth in babies fed certain types of formula.

They also support the message that "what happens to the child's diet after a year is probably much more important," said Dr. Michael Kramer, who researches infant feeding at The Montreal Children's Hospital and wasn't involved in the new report.

The study included 1,840 infants who were born in Germany between 1995 and 1998. Those infants were fed one of four different kinds of formula -- including cow's milk formula and other "hydrolyzed" formulas that have broken down, easy-to-digest proteins -- or exclusively breastfed.

The kids were at risk for allergies and researchers were also testing whether certain kinds of formulas could protect them from allergic reactions later in life.

In past studies, the same researchers reported that when they brought the babies back in for a one-year check-up, those fed one kind of hydrolyzed high-protein formula had gained less weight, on average, than the other formula and breast-fed babies.

But in this study, when about half of the kids returned at age 10, there was no difference in their body mass index, a measure of weight in relation to height.

That suggests there are "no long-term consequences" for BMI from cow's milk or hydrolyzed formulas, Peter Rzehak from Dr. von Hauner Children's Hospital in Munich and colleagues report in the American Journal of Clinical Nutrition.

"This particular formula that led to a reduction in weight gain... probably smelled bad and tasted bad," Kramer said. "That's probably why the babies didn't grow as well in the first year."

But, he added, the "catch-up" after that first year is consistent with findings from other research, including his own.

"Whatever changes occur due to feeding in the first year are probably a drop in the bucket in terms of affecting weight gain over the long term," Kramer told Reuters Health.

Researchers added that it's still unclear how early growth and breastfeeding or formula use may affect childhood obesity. Because of a wide range of health benefits for babies -- from fighting infections to IQ -- the World Health Organization recommends exclusive breastfeeding for the first six months of life, and continued breastfeeding until kids are at least two years old.

Alison Ventura, a nutrition scientist at Drexel University in Philadelphia, said that early weight gain isn't only about what babies are fed, but how they are fed.

"The parent has more control, in theory, during bottle feeding, so that they might feed in response to how much is left in the bottle rather than the infant's cues," which might be too much in some cases, she told Reuters Health.

She also cautioned against taking too much from the current findings, because they represented a specific group of babies with a family history of allergies.

Kramer agreed that parents should be aware of how much formula or breast milk they're feeding their infants and said that "it's almost never too early" to make sure very young kids aren't over-fed and are getting enough physical activity.