“We know that we have children with clinical obesity at age two, which makes you more likely to be overweight as a teen and into adulthood,” says Ben Gibbs, a professor of sociology at Brigham Young University. Gibbs co-authored a recent study in the journal Pediatric Obesity that found clinical obesity at 24 months was strongly correlated to formula feeding in infancy.

The team studied 8,000 mothers with nine-month-old babies, asking them whether they predominantly breastfed or formula-fed or did both, and then evaluated the child’s weight at age 2. Babies put to bed with a bottle were 30 percent more likely to be obese at age 2. Those fed solid food before four months were 40 percent more likely to become obese.

Gibbs says his research suggests that babies who are mostly bottle-fed don’t always learn how to regulate their appetites the same way as breastfed babies, and that parents may tend to overfeed when they’re looking at a bottle of milk and measuring a baby’s serving in ounces (something a mom doesn’t do when she breastfeeds).

“The takeaway here,” Gibbs says, “is that the habits we adopt early on for our babies matter later in life.” The study doesn’t mean your baby will be overweight if he is bottle-fed at night, he assures new parents. But while obesity has a lot to do with genetics and biology, Gibbs says his research does tell parents to be mindful of a baby’s feeding practices in the first few months of life.