Bottle Feeding and an Increased Risk of Obesity

Bottle Feeding BabyBefore I went back to work at the beginning of April, I was worried about feeding my daughter in my absence. Up until going back to work, I had exclusively breastfed her. I had also been pumping in an effort to create a stockpile of frozen expressed breast milk. However, my daughter hated her bottle and all other feeding devices. My husband and I had tried a bottle, multiple sippy cups, a spoon, a cup, and an eye dropper. However, my smart little daughter knew where the good stuff was and wanted nothing as second rate as pumped milk. She is still not a big fan of her bottle, but she will eat my pumped milk when she gets hungry enough while I am at work. On average, she eats between two and five ounces while I am gone for six hours.

Following the ounce per hour rule, I know that my daughter is getting just enough milk while I am away that she is not starving by the time I get home and can breastfeed her. And, actually, I must admit that I am rather pleased that she prefers breastfeeding straight from me over drinking my pumped breast milk from a bottle. Her preference in conjunction with the ounce per hour rule has helped to prolong our breastfeeding relationship.

Additionally, I recently became aware that bottle feeding in general and not just bottle feeding with breast milk is associated with an increased risk of obesity. I was worried at first that my daughter hated her bottle. Now I am relieved and a little grateful.

In a recent study conducted by Ruowei Li, MD, PhD; Joselito Magadia, PhD; Sara B. Fein, PhD; and Laurence M. Grummer-Strawn, PhD as published as “Risk of Bottle-feeding for Rapid Weight Gain During the First Year of Life” in the May 2012 issue of Archives of Pediatrics & Adolescent Medicine, researchers concluded that the mode of milk delivery and not just breast milk versus formula affected the risk of obesity.

The study had two specific hypotheses: (1) Infant weight gain is not only affected by type of milk but also by mode of milk delivery, and, (2) regardless of the type of milk in the bottle, bottle feeding might put infants on a faster track of weight gain.

To test their hypotheses, the researchers recruited pregnant women in their third trimester of from a consumer opinion panel of approximately 500, 000 households throughout the United States between May 2005 to June 2007. Approximately 3,000 babies participated in the study. The infants were classified into one of six mutually exclusive feeding categories: (1) breastfed only, (2) breastfed and human milk by bottle, (3) breastfed and nonhuman milk by bottle, (4) Human milk by bottle only, (5) human and nonhuman milk by bottle, and (6) nonhuman milk by bottle only. Infant weight was measured at three, five, seven, and twelve months. Researchers also controlled for other potentially confounding effects such as maternal age, race and ethnicity, pre-pregnancy body mass index, infant sex, gestational age, age at introduction of solid food, and birth weight.

Despite the belief that breast milk (and not just breastfeeding) is best for human infants, the researchers discovered that babies who were exclusively breastfed gained weight more slowly than babies who were bottle fed regardless of the content of the bottle (breast milk or formula). Furthermore, weight gain was negatively associated with proportion of breast milk feedings but positively associated with proportion of bottle feedings among the babies who received mostly breast milk. As the researchers concluded:

Infant weight gain might be associated not only with type of milk consumed but also with mode of milk delivery. Regardless of milk type in the bottle, bottle-feeding might be distinct from feeding at the breast in its effect on infants’ weight gain.

In other words, breastfeeding, not just breast milk, lowers the risk of obesity. Bottle feeding, either pumped breast milk or formula, subsequently increases the risk of obesity.

Why might bottle feeding and not just formula feeding put babies at an increased risk for obesity? One hypothesis is that babies who breastfeed are better able to self-regulate their energy intake. Breastfeeding requires more effort and energy than bottle feeding, so breastfeeding babies might stop eating when full as opposed to continuing to suckle on a bottle.

Second, and perhaps more importantly, bottle feeding allows a caregiver to monitor the amount of milk or formula that a baby drinks. Caregivers might be more likely to push a baby to finish a bottle than to push a baby to breastfeed for longer. After all, formula costs money, and pumped breast milk is often equated to liquid gold. Many caregivers just do not have the heart to toss out even an ounce of uneaten milk and so will encourage a baby to continue to eat even after he or she is full. Encouraging a baby to continue to eat despite no longer being hungry overrides his or her satiety mechanisms and sets him or her up for a lifetime of eating problems and obesity.

Pumped Breast MilkFortunately for my daughter, my husband never forces or even encourages her to finish her entire bottle of milk. He offers her the bottle multiple times while I am away. If she is hungry, she eats. If not, then he does not force the issue. Most days, he ends up throwing out about half an ounce and even as much as three ounces. (Although, sometimes if the leftover milk has not been out too long, I will use the healing power of breast milk at the end of the day to treat diaper rash and any scratches that my daughter may have given herself throughout the day.) We know that she will eat as much as needs to to keep from starving. And, as soon as I get home, she nurses the rest of the evening until her heart (and tummy) is content.

A bottle is a useful tool for feeding a baby when the mother simply cannot be around to breastfeed. When I am at work, my daughter will eat a little of my pumped breast milk from her bottle. However, because bottle feeding is linked to an increased risk of obesity, my husband and I never push her to eat more from the bottle than she wants. We also instruct all of her other caregivers such as my parents to feed her only as long as she is hungry and never to force her to empty a bottle. I would rather throw out a few ounces of breast milk now than set my baby up for a lifetime of weight problems.

What do you think about the research that links bottle feeding and not just type of milk with an increased risk of obesity?


Bottle-feeding and obesity risk:
Li, Ruowei, Joselito Magadia, Sara B. Fein, & Laurence M. Grummer-Strawn. 2012. Risk of bottle-feeding for rapid weight gain during the first year of life. Archives of Pediatrics & Adolescent Medicine 166(5). 431-436.

Image Credits

Bottle Feeding Baby:
Pumped Breast Milk © 2012 Heather Johnson

Heather Johnson

Heather Johnson is a mother, wife, writer, librarian, and linguist. She earned a BA in English studies with a minor in creative writing from Illinois State University in May 2007, an MS in library and information science from the University of Illinois at Urbana-Champaign in May 2009, and an MS in English studies with an emphasis in linguistics at Illinois State University in December 2011.

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