Babies who are exclusively formula-fed from larger bottles may be at risk of greater weight gain in infancy and, in turn, of obesity later in life.
“There has been quite a bit of research around the relationship between container or plate size and food intake for adults, and we wanted to explore whether the same relationship exists early in life with bottles,” says Charles Wood, lead author of a new study in the journal Pediatrics.
The findings show that infants who regularly drink from a large formula bottle (greater than 6 ounces) by the time of their two-month well visit exhibit greater weight gain and weight-for-length size than infants of comparable age. The weight gain is independent of other factors.
“Growth in infancy is complex,” Wood says, “but bottle size may be a risk factor for rapid weight gain and, in turn, later obesity.”
For the study, researchers followed 379 exclusively formula-fed infants from the Greenlight Intervention Study, a cluster randomized trial to prevent childhood obesity, starting at their two-month well visits through their six-month well visit.
Parents brought in the bottle they were using and showed how much formula was being given to the infant at feeding time or were asked to choose a bottle similar to the ones they typically used at home.
By the time of the six-month visit, infants fed formula exclusively from large bottles had gained nearly half a pound (7.4 ounces) more than those who were fed with smaller bottles.
Weight gain varies widely among infants, but it is important for parents to establish an understanding of appropriate hunger and fullness cues, whether the child is receiving formula, breastmilk, or a combination of both.
“The exciting part of this study is to think about the fact that this relationship between weight gain and container size may start really young—younger than we thought,” says senior author Eliana Perrin, professor of pediatrics.
“This gives us some novel things to think about when we are trying to prevent obesity—a major public health problem. A lot of us eat more when our food is on larger plates—even when we are not hungry for it.”
“The large size of the bottle combined with pressuring the baby to finish it may not be as healthy for our babies as remembering that we all have hungry days and less hungry days.”
The researchers previously reported that larger bottles are associated with more daily intake of formula. But they say more research is needed to completely understand the link between bottle feeding and obesity risk to help inform interventions.
“There is a whole host of bottle sizes and types out there that are marketed to parents, and for some, a bigger bottle may be chosen because of cost, availability, or other factors,” Wood says.
“Regardless of the bottle size, adults who are feeding the infant need to have a ‘bidirectional’ relationship during each feeding. That means not being distracted by the phone or the television, and watching for cues that the baby is full.
“What our study helps uncover is that the size of the bottle may be one of several ways we can optimize healthy weight gain in the first year of life.”