Could mothers be putting their children on a path toward obesity from the very first days of their lives?
A study published online Monday in the journal Pediatrics finds that babies fed a particular type of infant formula put on more weight than other babies and continued to gain weight faster than their counterparts during the first 7.5 months of life.
Researchers from the Monell Chemical Senses Center in Philadelphia wondered whether babies would respond differently to formulas based on cow’s milk (whose proteins are intact) and those made with proteins that are pre-digested, which are easier for some babies to tolerate. These formulas, known as protein hydrolysate formulas (or PHFs), have about 35% more protein than cow’s-milk formulas. They also have more free amino acids.
The researchers recruited 56 mothers who had already decided to give their babies formula – 32 of them were randomly assigned to get cow’s-milk formula and 24 got the PHF formula. Mothers didn’t know which type of formula their infants received. Babies in both groups had similar birth weights and lengths, and mothers in both groups were of similar age, race, ethnicity, BMI and income.
The differences between the two groups became apparent after only 2.5 months. By then, the babies receiving cow’s-milk formula had significantly higher weight-per-length than the babies on PHF formula. By 3.5 months, the cow’s-milk formula babies also had significantly higher weight-per-age than the PHF babies, whose weight (per length and per age) matched those of breast-fed babies.
The babies who got cow’s-milk formula added to those early gains throughout the course of the study, even though both groups started eating solid foods at about the same time.
Formulas made with cow’s milk are the most popular type on the market. Are they making babies fat, predisposing them to being overweight kids and obese adults?
Perhaps, the researchers say. As they write in the study, they can’t be sure why the cow’s-milk formula led to more weight gain, but they have a leading theory.
They speculate that the free amino acids in the pre-digested formula did a better job of stimulating receptors in the mouth and gut that signal to the brain that the stomach is full and it’s time to stop eating. Though babies in both groups spent about the same amount of time eating at each feeding (between 11 and 12 minutes), the babies on the PHF formula drank less during that time before pushing the bottle away.
“Because dietary and nutritional programming can have long-term consequences in terms of later development of obesity, diabetes and other diseases, it is imperative that we learn more about the long-term consequences of the early growth differences caused by environmental triggers, such as those associated with infant formulas,” they conclude.