Mommy, Mommy, How Does Your Baby Grow?

Bottle fed babies gain more weight than breastfed babies regardless of what is in the bottle

(RxWiki News) When it comes to feeding babies, it's not just what you feed your child but how you feed your child. Even breastmilk in a bottle affects weight gain differently than milk directly from the breast.

A recent study has found that infants fed only by bottle gained more weight each month than if they were only breastfed, regardless of whether the bottle had breastmilk or another food.

"Breastfeeding is better than bottle - when possible."

Lead author Ruowei Li, PhD, a researcher at the Centers for Disease Control and Prevention and the Division of Nutrition, Physical Activity and Obesity at the National Center for Chronic Disease Prevention and Health Promotion, and colleagues to investigate how feeding practices affect babies' weight gain.

Past research has already shown that breastfed babies are at a lower risk for childhood obesity and that the feeding practices used with infants plays a part in how their bodies grow during their first year.

Therefore, the researchers recruited U.S. women through a mail panel from May 2005 to June 2007 and ended up with 1,899 babies that had at least three weight measurements during their first year.

The women were mostly white, married and aged 25 to 34, with some education past high school. About half were overweight or obese before they became pregnant.

The researchers surveyed the women nearly every month during their baby's first year, asking how often they breastfed, pumped breastmilk to feed from a bottle, fed their baby formula and fed their baby other types of milk in the past week.

The researchers divided the children into six categories: breastfed only; breastfed and human milk by bottle; breastfed and nonhuman milk or formula by bottle; human milk by bottle only; human and nonhuman milk or formula by bottle; and nonhuman milk or formula by bottle only.

The women reported their babies' weight at 3 months, 5 months, 7 months and 12 months based on the most recent doctor's visit and that visit's date. The researchers then used a formula to standardize the weight gain rates for the babies so they could compare the numbers.

The researchers found that babies fed only nonhuman milk or formula by bottle gained the most weight over the period from 3 months old to their first birthday. Overall, babies gained more each month when eating from a bottle than being breastfed, no matter what they were eating.

Babies who ate only breastmilk from a bottle gained an average 89 grams (0.2 pounds) more each month compared to babies who were exclusively breastfed at the breast. Babies who ate nonhuman milk from the bottle gained an average 71g more per month.

But those who were fed both breastmilk and nonhuman milk from a bottle only gained about 37g more each month than exclusively breastfed babies. Babies who ate formula and were breastfed gained about 45g more each month.

Babies who drank only breastmilk, both at the breast and by bottle, gained weight at the same rate as babies who only ate from the breast.

For those babies who were only fed breastmilk by both breast and bottle, their weight gain each month increased from 729g to 780g when they went from only a few bottle feedings to eating mostly from the bottle.

Interestingly, exclusively breastfed babies actually lost a tiny amount of weight when their number of times nursing was increased a little bit (a 10 percent increased led to 3.6g weight loss), but the opposite was true for babies fed by bottle. Eating more often from the bottle led to more weight gain.

The researchers determined that there might be several reasons for the findings.

"Regardless of milk type in the bottle, bottle-feeding might be distinct from feeding at the breast in its effect on infants' weight gain," the authors wrote.

They discussed the ability of breastfed infants to self-regulate how much they eat as one possible reason, and/or the possibility that breastfeeding mothers develop a "less controlling" feeding style with their babies.

The researchers adjusted their findings to account for mother's age, race/ethnicity, education level, family income, marital status, number of children and pre-pregnancy weight as well as mothers' participation in the WIC (Special Supplemental Nutrition Program for Women, Infants, and Children).

The researchers took into account the baby's gender, gestational age (how many weeks mom was when she gave birth), birth weight, age when they began eating solid food, and how many sweet drinks they drank on average each day during their first year, such as juice, soda, Kool-Aid, etc.

In an accompanying editorial article, Robert Whitaker, MD, a professor of Public Health and Pediatrics at Temple University, and Jeffrey Wright, MD, of the Department of Pediatrics at the University of Washington School of Medicine, discussed the implications of the study, including the possibility that lower risk of obesity is more related to the act of breastfeeding rather than just eating breastmilk.

They listed three possible reasons babies might be fed breastmilk from a bottle rather than only from the breast: the mothers need to work, the fathers or other caregivers, such as grandparents, want to help feed the baby, and the parents want to see how much their baby is eating.

Whitaker and Wright cautioned that it may not always be possible for women to breastfeed or to breastfeed exclusively, so pediatricians should take the reality of women's lives into account when advising them.

"Pediatricians should deliver their expert advice with empathy, being mindful of the gap that always exists for parents between doing what it ideal for their children and doing what is possible," they wrote.

The articles appeared in the May issue of the Archives of Pediatrics & Adolescent Medicine. The research was funded by the Food and Drug Administration, the Centers for Disease Control and Prevention, the Office of Women's Health, the National Institutes of Health and the Maternal and Child Health Bureau in the U.S. Department of Health and Human Services. No conflicts of interest were reported.

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Review Date: 
May 7, 2012