It's normal for newborns to lose weight during the first few days after birth. But weight loss can differ substantially depending on whether a baby is formula-fed or breastfed, according to researchers at the University of Manitoba in Canada. Exclusively formula-fed babies tend to lose much less weight than breastfed babies and those who are breastfed but receive supplemental formula. Since a loss of 5 percent to 7 percent of body weight is normal in the first few days, it could be that formula-fed babies are initially overfed, said the authors.
The study is important because overfeeding early in life may "hardwire" a baby's metabolism and influence weight later in life. Other studies have shown that breastfed infants tend to have lower obesity rates in adulthood.