Bottle-feeding and weight gain in infancy: Does it matter what’s in the bottle?

This baby looks delicious (

Fearless Husband and I have embarked on a 2-week “cleanse”, meaning we are only eating whole, organic, mostly raw foods. Meaning mommy is without her little helpers, Sugar and Caffeine. Meaning mommy is ornery.

Thus, I hope you’ll pardon the snarkiness which I’m sure will creep in to the following post. I’ve been trying to hold back lately, in the spirit of creating a kinder, gentler, more “professional” FFF, but the lack of food is bringing me back to my obnoxious roots. And it certainly doesn’t help that the study I’m about to dissect is about weight gain in babies (chubby, delicious babies… not that I’d ever eat a baby or anything, being vegetarian and, you know, not a cannibal. Unless the baby was dunked in chocolate… or rolled up in a nice fluffy tortilla….oh my god, I need sugar….) which is one of my biggest pet peeves.

I stumbled upon the study in question via this article, Bottle Feeding Linked to Rapid Weight Gain in Infants, Possible Obesity Risk. Great title, right? The article is correspondingly anxiety-provoking:

In a surprise twist to the “breast is best” debate, bottle feeding, and not just formula feeding, increases the risk of rapid weight gain in infants, leading to an increased risk of obesity later in life, says a recent study published in the Archives of Pediatrics & Adolescent Medicine...The results of the study indicate that breastfeeding, and not just breast milk, is best for babies. Infants who were exclusively formula fed by bottle gained only between 71 and 89 grams more per month than infants who were exclusively fed human milk by bottle. Furthermore, weight gain was negatively associated with the proportion of breast milk feedings but positively associated with proportion of bottle feedings among the infants who received mostly human milk…. In other words, bottle feeding, and not just formula feeding, puts children at an increased risk for rapid weight gain during infancy and for obesity later in life. Breastfeeding, and not just breast milk, is best in terms of maintaining a healthy weight.

Okay, so reading this, I felt conflicted: on the one hand, I am pleased as punch that researchers are looking at differences in the types of milk fed by bottle, and comparing human milk fed by breast to human milk fed by bottle – these are the types of studies that can potentially help us figure out if it something in breastmilk (which could then possibly be recreated to make a better formula) conferring certain benefits, or if it is the act of breastfeeding itself. If it is the latter, then this has obvious implications for working women, and exclusive pumpers, many of whom go to extreme lengths to provide the health-enhancing benefits of breastmilk for their babies. But on the other hand… if this was yet another study linking bottle-feeding to obesity, it wouldn’t really be doing much more than creating more stress and pressure on mothers who were unable to exclusively breastfeed – especially if those who were combo-fed fell prey to the same dreaded weight gain as formula-fed babies.
A quick jump over to the actual study (which is available to the public, free of charge, so I highly recommend taking a gander. It’s always better to go directly to the source. Kind of like my current diet…did I mention I was hungry?) quickly put both my excitement and my fears to rest. And here is why:
1) The study was based on phone surveys done with mothers, who reported both the mode of feeding and infant weight gain. Self-reported information is pretty much the bottom of the barrel when it comes to solid scientific data. It’s notoriously shaky as evidence goes, and especially with something like infant feeding where there is a strong, socially-induced morality/pride factor (especially considering the majority of the women involved were white, middle class, and college educated –  the group mostly likely to initiate breastfeeding and be well versed in the benefits), what someone tells you and what they actually do might be two entirely different things. Point being, this isn’t exactly hard data. Even the weights may have been misreported. The researchers could have asked for physician records to back up their results, but they didn’t.
2) More importantly – the study had fudge-all to do with childhood obesity. All it looked at was the rate of weight gain in the first year. Now, one could take these results and merge them with other studies which associated faster weight gain in infancy to later obesity, but then you’re just taking two observational, intricately confounded studies and throwing them together like a Glee mashup: same old songs, dressed up in a fancy arrangement. This study did not discuss whether the babies were gaining appropriate amounts of weight; we don’t know if the exclusively breastfed babies on the lower end of the curve were underweight or normal, or if the exclusively formula-fed or mixed-fed babies (on the other end) were overweight. All of these babies could have been within normal limits – we’re talking grams here. 

I think it’s a rather daring leap to take self-reported data that shows differences in the rate of weight gain in the first year of a child’s life, and use it to justify the message that “Feeding at the breast needs to be the first feeding choice for babies. When feeding at the breast is not always feasible, supplementing breastfeeding with expressed breastmilk is a good alternative, but special attention is needed for infants’ internal feeding cues while bottle-feeding,” which is exactly how the study authors capped off their conclusion. Where is the discussion of why weight gain in the first year is bad?

Interestingly, the researchers also found that “Infants categorized as consuming ‘human milk by bottle only’ and ‘nonhuman milk by bottle only’ gained more weight than infants fed at the breast only, but there was no such bottle effect observed among infants categorized as consuming ‘human and nonhuman milk by bottle.’” They hypothesize that:

“…(t)his might be owing to the fact that infants in this mixed feeding category were more likely fed at the breast previously than the other 2 groups (data not shown). Our previous study suggests that infants fed at the breast develop a better self-regulation of milk intake, which may be carried over even after feeding is transitioned from breast to bottle. Similarly, mothers who previously breastfed might better recognize infants’ cues of hunger and satiety, which may last even after they stop breastfeeding.”

I view this as a prime example of the Achilles heel of infant feeding research. When your internal bias is strongly in favor of one outcome, it’s too easy to extrapolate. First of all, how did they come to the conclusion that the women feeding both breastmilk and formula by bottle breastfed longer than those feeding exclusively breastmilk by bottle? Perhaps this came from additional survey findings, but since we don’t see this data, I’m going on the assumption that this was simply the authors’ hypothesis.  I think it is an equally plausible explanation that women who are feeding both breastmilk and formula by bottle (this is a group with no physical breastfeeding, remember) were exclusive pumpers, just like the other group, who decided to add formula in at some point. As a former exclusive pumper, every drop you pump is worth it’s weight in gold. If anyone’s going to be “encouraging” a baby to finish what’s in his bottle, wouldn’t it stand to reason that it would be the woman who worked her ass off to provide it’s contents? Perhaps the mixed-feeding group didn’t feel as much pressure to make sure that their babies got every last drop, which helped reduce the risk of overfeeding. (PLEASE note that I am in NO WAY insinuating that all exclusively pumping moms overfeed their kids. I don’t think this, at ALL. I am simply providing an alternative hypothesis that I believe is equally plausible to highlight the tunnel vision so prevalent in this area of research.) Alternately, maybe the act of exclusive pumping makes milk less “filling” in some way (the researchers do briefly discuss hindmilk versus foremilk, which can get a bit screwy with pumped milk, especially if you are combining milk from different pumping sessions) and adding a bit of formula helped the mixed-fed babies feel more full. Regardless, my point is that there are other rational (and perhaps more interesting, in terms of future research) explanations than the one provided by this study’s authors.

You’ve all heard my rants on this before, but I am seriously sick of studies that examine weight gain in babies and attempt to use it as fodder for the childhood obesity hysteria. I read another article about a separate study today, which correlated c-sections with later obesity in infants, and felt the same frustration. This article questioned why, as the rates of c-sections have gone up, so have the rates of obesity. I think this is like asking why the rates of autism have gone up along with the rates of breastfeeding. It’s ridiculous. Childhood obesity is high in this country because our kids eat like crap and sit in front of screens all day. It’s hard to change these behaviors, when you’re on a limited budget, living in areas with poor food options, and working all day to keep a roof over your kids’ heads. And being a little heavy isn’t even a bad thing, as long as you are eating healthfully and moving your body – some folks are genetically predisposed to being a little more fluffy. It’s about overall health, not body weight, and much of the conversation around weight gain and body size seem to ignore all of these considerations in favor of overreaching studies that attempt to pin blame on individuals, while refusing to see them as individuals.

And speaking of that, I’m about to shut down my screen, go drink a glass of spinach and kale juice, and dream about eating crap. Crap is delicious. Which is why is is so much fun to blame our propensity towards pudge to the way our mothers birthed and fed us.

About the Author:

Suzanne Barston is a blogger and author of BOTTLED UP. Fearless Formula Feeder is a blog – and community – dedicated to infant feeding choice, and committed to providing non-judgmental support for all new parents. It exists to protect women from misleading or misrepresented “facts”; essentialist ideals about what mothers should think, feel, or do; government and health authorities who form policy statements based on ambivalent research; and the insidious beast known as Internetus Trolliamus, Mommy Blog Varietal.

Suzanne Barston – who has written posts on Fearless Formula Feeder.


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