New study claiming formula increases obesity has a disabling flaw: an arbitrary designation of infant obesity

68592044 - illustration of flawed text buffered on white background

The headline, Infant formula could change gut bacteria, contribute to childhood obesity, is alarming.

The findings are worrisome:
[pullquote align=”right” cite=”” link=”” color=”” class=”” size=””]If they had used a growth chart of how all infants grow, not merely breastfed infants, the title might easily be ‘Exclusive Breastfeeding and the Risk of Underweight in the First Year of Life.’[/pullquote]

A new study shows that babies who were breastfed had different bacteria environments, or microbiomes, in their guts –- and lower obesity levels as they grew -– than babies who were primarily fed formula…

For the study, published in the Journal of Pediatrics [sic], researchers in Canada looked at data from the Canadian Healthy Infant Longitudinal Development, or CHILD, focusing on the first year of life for more than 1,000 infants from four different sites.

Researchers in this study wanted to know if only breastfeeding, breastfeeding plus some early foods, or formula feeding alone affected the type of bacteria found in the infants’ guts at two ages: 3 to 4 months and 12 months.

What did they find?

Of the formula-fed babies, 33 percent were overweight or at risk of being overweight, while 19 percent of exclusively breastfed babies were overweight or at risk.

There’s a serious problem with the study, however. It uses a flawed and arbitrary measure of infant obesity.

The paper is Association of Exposure to Formula in the Hospital and Subsequent Infant Feeding Practices With Gut Microbiota and Risk of Overweight in the First Year of Life.

The authors report:

There were 1087 infants in the study (507 girls and 580 boys); at 3 months, 579 of 1077 (53.8%) were exclusively breastfed according to maternal report. Infants who were exclusively formula fed at 3 months had an increased risk of overweight in covariate-adjusted models (53 of 159 [33.3%] vs 74 of 386 [19.2%]; adjusted odds ratio, 2.04; 95% CI, 1.25-3.32). This association was attenuated (adjusted odds ratio, 1.33; 95% CI, 0.79-2.24) after further adjustment for microbiota features characteristic of formula feeding at 3 to 4 months …

Here is a chart of the results.


How did they determine which babies were “obese”?

At 12 months of age (mean [SD] age, 12.4 [1.3] months), infants were weighed and measured by CHILD Study staff. Age- and sex-specific weight for length z (WFLz) scores were calculated according to World Health Organization standards. A WFLz score greater than the 97th percentile was considered overweight, and a WFLz score greater than the 85th percentile was considered at risk for overweight …

But breastfed babies and formula fed babies grow differently. The CDC acknowledges:

The WHO growth charts reflect growth patterns among children who were predominantly breastfed for at least 4 months and still breastfeeding at 12 months. These charts describe the growth of healthy children living in well-supported environments in sites in six countries throughout the world including the United States. The WHO growth charts show how infants and children should grow rather than simply how they do grow …

The WHO growth charts establish the growth of the breastfed infant as the norm for growth. Healthy breastfed infants typically put on weight more slowly than formula fed infants in the first year of life. Formula fed infants gain weight more rapidly after about 3 months of age. Differences in weight patterns continue even after complementary foods are introduced

Wait, what? Formula fed infants are being evaluated on a scale designed for breastfed infants?

To understand why that’s a serious problem it’s instructive to consider the genesis of the current WHO standards. Previous standards evaluated growth based predominantly on formula fed infants since most infants were formula fed at the time they were developed. Many breastfed infants were diagnosed as underweight using these charts. Breastfeeding advocates claimed that it was wrong to evaluate breastfed infants using formula fed infants as the standard.

They had a point, but it’s not clear that it was a valid one. It’s based on the assumption that every breastfed infant is fully fed when the reality is that breastfeeding has a significant failure rate and some breastfed babies are actually underfed. Far fewer babies receiving formula are underfed since they can eat until satiety instead of merely until the milk runs out.

The WHO charts purportedly show “how infants and children should grow rather than simply how they do grow.” But they don’t measure how infants “should” grow, they measure how breastfed infants, including underfed infants, grow. It’s a classic example of the naturalistic fallacy: if something is a certain way in nature, that’s how it ought to be. But that’s makes as much sense as constructing a child growth chart including those with rickets to evaluate contemporary children who have easy access to calcium and vitamin D.

It’s not clear at all that any of the purportedly obese infants in this study would be considered obese if the authors used a growth chart of how all infants grow, not merely breastfed infants. In that case, the title of the study might be ‘Exclusive Breastfeeding and the Risk of Underweight in the First Year of Life.’

This paper is yet another example of white hat bias.

‘White hat bias’ (WHB) [is] bias leading to distortion of information in the service of what may be perceived to be righteous ends… WHB bias may be conjectured to be fuelled by feelings of righteous zeal, indignation toward certain aspects of industry, or other factors. Readers should beware of WHB and … should seek methods to minimize it.

Breastfeeding researchers are so sure that breastfeeding is beneficial, and are so hostile to the infant formula industry that they arrange their data in ways that promote breastfeeding and demonize formula. Creating and employing infant growth charts that assume that breastfeeding is always best for every baby is bias in the service of what are perceived to be righteous ends. But it’s bias nonetheless and it’s wrong.

And that makes the conclusion of this study entirely arbitrary.

54 Responses to “New study claiming formula increases obesity has a disabling flaw: an arbitrary designation of infant obesity”

  1. Eric Bohlman
    June 25, 2018 at 7:35 pm #

    How did this one get past the reviewers?

    “This association was attenuated (adjusted odds ratio, 1.33; 95% CI, 0.79-2.24) after further adjustment for microbiota features
    characteristic of formula feeding at 3 to 4 months.”

    “Was attenuated?” Attenuated my ass! It DISAPPEARED. It’s pushing up the daisies. It’s a stiff. Bereft of life it rests in peace. It has rung down the curtain and joined the choir invisible. An odds ratio which, after adjustment, has a confidence interval that includes 1.0 is an ex-association.

    The common euphemism for this is “advocacy science”.

  2. Dr Kitty
    June 10, 2018 at 7:21 am #

    My sister had her first baby!
    In the U.K.
    She has planned a hospital birth in the MLU, but it didn’t quite go to plan.
    She went into labour at 4am, the community midwife came to her house at 6am to make sure she was ok and to stay with her until it she was at 4cm and ready to go to hospital…except she was already 9cm!
    At that point she decided she wasn’t really up for an ambulance ride to hospital, and decided to stay at home, given everything had gone so fast and she felt able to cope. Two more midwives arrived, she laboured down for an hour, pushed for 90minutes, was told clearly that if baby hadn’t arrived in 20minutes an ambulance would be dispatched and baby arrived 10 minutes later. Not even a tear and both mother and baby doing great.

    That’s how you have safe homebirths in a well integrated, well run system.
    I am incredibly relieved.

    • Dr Kitty
      June 10, 2018 at 8:10 am #

      Should say- three MWs because 6am MW was due to go off duty at 8:30 and they didn’t want to risk any chance of only one person being with her. In the end baby arrived at 9am on the dot and MW decided to stay past the end of her shift because she didn’t want to miss the birth.

    • Sarah
      June 10, 2018 at 1:40 pm #

      Congratulations to the family!

    • momofone
      June 11, 2018 at 12:08 pm #


    • June 11, 2018 at 12:32 pm #

      Congratulations! I’m delighted that everything went so well. May your sister and her new little one continue to enjoy excellent health.

    • MaineJen
      June 11, 2018 at 12:39 pm #

      Wow!! What a story she has now 🙂 So glad everything went well!

  3. Roadstergal
    June 8, 2018 at 5:45 pm #

    “Previous standards evaluated growth based predominantly on formula fed infants since most infants were formula fed at the time they were developed.”

    So the FF curve was made in the ’70s?

    When we were teenagers in the ’80s, did we have an obesity epidemic? No? Then don’t rename a FF growth curve as obese.

    • BeatriceC
      June 8, 2018 at 5:47 pm #

      Except me. I was breastfed in the 70’s and overweight in the early to mid-80’s, then got super active and slimmed down in the late 80’s and early 90’s. I’m obese again, but that’s complicated. I need a therapist for real to work through my very complicated issues with food.

    • Heidi
      June 8, 2018 at 6:10 pm #

      I don’t even recall childhood obesity being an issue when I was a kid in late 80 and throughout the 90s. Morbid obesity was literally like 4 kids among a couple of thousand. Even what one might call chubby wasn’t that common. This was in the heyday of juice, sugary cereals, advertising food to kids, and high fructose corn syrup. No one thought twice about going to McDonald’s for a happy meal. We were formula fed, had rice cereal in our bottles, and started on Gerber before six months. It’s almost like there’s more to it and it’s not as simple as these people make it out to be. . .

    • Gæst
      June 13, 2018 at 3:37 am #

      I was thinking this as well. If there is an “obesity epidemic,” it’s going to be multi-factoral. My daughter was born premature and a little small for gestational age due to a small placenta. At six weeks of age, a neonatologist told me she was at higher risk of obesity and diabetes when she hit puberty as a result. I dug up more information later, and it seems it’s related to epigenetics: if her small placenta restricted her calories as she developed, it may have “switched on” genes the prepared her for a life of scarce food, either making her body hold onto calories more fiercely, or maybe affecting her hunger cues. But the point here is that she thrived as an infant due to modern medicine. In the past – the past where there was no “obesity epidemic” – she would have been at much higher risk of not surviving childhood. As a premature NICU baby, she also would have been much more likely to be formula fed. How do you disentangle all this?

  4. fiftyfifty1
    June 8, 2018 at 5:40 pm #

    Gosh there were so many potential headlines here:

    New study claiming formula increases infant obesity has a disabling flaw:
    A. “an arbitrary designation of infant obesity”
    B. “a ridiculously short follow up”
    C. “too many confounders to list”
    D. “absolutely no evidence of impact on health outcomes”
    E. “a pathetically weak study design”

    Sheesh, I bet it was hard on Dr. Tuteur to have to choose just one!

  5. lawyer jane
    June 8, 2018 at 4:50 pm #

    Here’s what the Ohio Sibling Concordance study found about obesity/BMI:

    “Some of the most notable findings from the current study concern physical health outcomes such as BMI and obesity. Findings from the few extant research efforts that examine the association between breastfeeding and the subsequent risk of obesity using sibling comparisons are conflicting (Gillman et al., 2006; Metzger and McDade, 2010; O’Tierney et al. 2009), even when the study sample used is from the same nationally representative dataset (Evenhouse & Reilly, 2005; Nelson et al., 2005). The results presented here suggest that unobserved family characteristics are likely to upwardly bias “typical” estimates of breastfeeding on BMI and obesity since regression coefficients from sibling comparisons for breastfeeding status are substantially attenuated toward zero while those for breastfeeding duration actually switch directions. These findings stand in sharp contrast to those from recent studies that attribute much of the Black/White disparity in obesity to racial differences in breastfeeding (Harder et al., 2005; Weden et al., 2012).”

  6. lawyer jane
    June 8, 2018 at 4:48 pm #

    And also, of course this connects to your previous post on the prevalence of breastfeeding. With so very few mothers exclusively breastfeeding at 3 and 6 months, there are obviously confounders.

  7. lawyer jane
    June 8, 2018 at 4:45 pm #

    How can it possibly be that even 20% of newborns are “overweight”?? This seems like strange research.

  8. Megan
    June 8, 2018 at 7:34 am #

    The other issue is WHY the infants were BF or FF. If the babies aren’t assigned to receive breastmilk or formula, bias is introduced by having nonrandom groups. For instance, I formula feed because my PCOS, a known risk factor for obesity and diabetes, causes me to have insufficient glandular tissue/severely decreased milk production. Are my children higher risk for obesity because they are FF or becauseof a genetic predisposition to obesity, PCOS and diabetes?

    • CSN0116
      June 8, 2018 at 7:42 am #

      They used a secondary data set. They didn’t get to design shit.

      Kramer’s PROBIT that was semi-randomized and followed BF/FF obesity rates through like 12 (?) years of age showed nothing (slightly more obese in the BF group, actually) is much better proof than this garbage.

      • The Bofa on the Sofa
        June 8, 2018 at 1:46 pm #

        You know, as the Probit study showed that there is no differencein childhood obesity between formula and breastfed, here is an alternate explanation of the author’s data:

        Brrastfed babies are undernourished

  9. CSN0116
    June 8, 2018 at 6:30 am #

    I take additional issue with this paper: what the FUCK is an “overweight” 3-month-old? Z-score be damned. What in the actual fuck is that?!

    2. It only followed babies for a measly year.

    • June 8, 2018 at 9:29 am #

      Seriously. My nephews were both fat babies, and are now lean, active, healthy 8- and 11-year-old boys. The weight dropped right off when they started walking.

      • The Kids Aren't AltRight
        June 8, 2018 at 12:51 pm #

        In contrast, I was a failure to thrive but exclusively breastfed baby that has struggled with her weight since early childhood. Without determining the relationship between babyhood weight and weight later on, the study is useless.

        • BeatriceC
          June 8, 2018 at 5:40 pm #

          Same here. I lost over two pounds of my birthweight and didn’t gain it back until I was six weeks old, and continued to gain slowly until my mother weaned me when she got pregnant with my sister (familiar story…that’s what happened with my middle and youngest too…almost like genetics plays a role in these things). I can kind of understand a little bit, because my mother is so tiny (89 pounds pre-pregnancy) and I was huge (10lbs 9oz), so she and her La Leche League friends and my first pediatrician kept blowing it off as just me correcting my size for assumed gestational diabetes (no actual diagnosis, just assumed based on my size). They failed to consider that my father and all of his siblings were all 10+ pound babies, and maybe I might have inherited his body type and not hers. But all my mom’s stories of how I was as a baby just scream “underfed, hungry baby”. She talks about how I nursed for 90 minutes at a time, in two hour cycles around the clock, so she only got a half hour break. And how I was grumpy and screamed a lot. And then my favorite story. When my oldest was a year old, my father and I went to this Chinese restaurant my parents frequented when I was little. The lady that owned the place recognized my dad and asked which kid I was, since it had been many years since she’d seen any of us kids. He told her and she responded “Ah! The screamer!”. Apparently, my mother would sit out in the car and nurse me, but as soon as I smelled food, I’d start screaming inconsolably, to the point where the owner and her staff would take turns walking me outside so my parents could eat. Looking back at those stories, combined with my weight loss and slow growth, I’m going to assume I was underfed.

          I have talked to other people with known or suspected food scarcity/underfeeding issues in their infancy and toddlerhood, and we all, without exception, have complicated relationships with food, and most of us struggle with being overweight. I have frequently wondered if these things are connected in any way, but I’m really not sure how one would go about attempting to look into that connection in any academically sound way.

          • The Kids Aren't AltRight
            June 8, 2018 at 8:12 pm #

            I also was a notorious screamer to the point where my parent’s (duplex) neighbors complained. I have also hypothesized that this is related to my later weight struggles. Even if there were a good way to study whether starving babies become overweight adults, there would be absolutely no interest in a study showing breastfeeding is less than perfect.

          • BeatriceC
            June 9, 2018 at 11:48 am #

            Honestly I don’t understand why they don’t want to. If they really truly wanted to increase long term breastfeeding rates like they say, they should be chomping at the bit to figure out why and how it fails, so they could then figure out how to fix it. Lots of women with supply issues would love to EBF if there was a way to increase production, but we’ll never figure that out as long as we keep sticking our fingers in our ears shouting “la la la la la, it’s perfect” instead of actually solving the problems.

          • The Kids Aren't AltRight
            June 9, 2018 at 11:52 am #

            I think they prefer claiming breastfeeding is perfect to actually raising breastfeeding rates.

          • BeatriceC
            June 9, 2018 at 12:49 pm #

            I’m pretty sure you’re right, since I think at the end of the day, Dr. Amy is right. They don’t care about any of the things they say they care about, and are only interested in keeping women attached to their babies.

          • Merrie
            June 9, 2018 at 12:05 pm #

            I was a chubby, happy, contented baby and haven’t gone on to have any weight issues as an adult. So there’s an n=1 for you haha.

          • BeatriceC
            June 9, 2018 at 1:00 pm #

            I really wish somebody would figure out a way to do an actual study. Anecdotes are, of course, not science, but when you get enough anecdotes saying the same or similar things, that should be a clue that it’s a topic worth studying. I can add my own kids and my niece to your story for more anecdotes on the “fully fed=better relationships with food as adolescents and adults” side of things.

            I just think it’s something that we really need to look into. It’s plausible and there are enough people reporting similar experiences that it’s at least worth a preliminary look over.

      • BeatriceC
        June 8, 2018 at 5:31 pm #

        My niece was the fattest baby I have ever seen. She was basically rectangular, almost square, and had fat rolls that would make the Michelin Man jealous. And then she learned how to walk and genetics made themselves obvious. She became tall and extremely skinny (think Twiggy), like her mother and grandmother, and most of her maternal line relatives (except me and a couple of my cousins). Also, she was EBF until solids were introduced, though I don’t recall at what age.

        • AnnaPDE
          June 11, 2018 at 10:17 am #

          This! My sister has a literally square face in some baby photos. My dad had lots of fun with finding the right crop to emphasise it. In her 10yo pics, she looks like she’s starving, and an underweight colt has nothing on her knobbly knees on skin-and-bone legs. These days she’s still extremely fit, but with a bunch of muscle from daily competitive sport.
          Oh and all of this on a diet of Nutella, milk and meat. No piece of carrot has passed her lips for the last 34 years.
          I guess genetics may have to do something with weight after all.

    • MaineJen
      June 8, 2018 at 11:22 am #

      I was thinking the same thing. If you can look at a 3 month old infant and think “Dang, that kid’s gotta lose some weight!” there is something wrong with you. Babies are supposed to be chubby.

      When my 8 year old was a baby, his little legs were too fat to fit in the Bumbo seat. Now he is a lean 50th percentile kid. This study is full of $%&^

      • Guest
        June 8, 2018 at 8:41 pm #

        There seems to be this weird, toxic obsession with obesity in the LLL/LC/natural childbirth educator subculture.

        At least that was my experience.

        • AnnaPDE
          June 11, 2018 at 10:12 am #

          The whole “healthy and natural” crunchy culture has that problem. My crunchy-affine coworker started obsessing about how she was surely on the straight path to becoming obese when she fell pregnant, and asked me to give her regular updates on that.
          She was completely fit and healthy. Maybe a tiny bit less firm than her usual perfect shape, but then she had headaches all the time and was also a bit scared to do too much of her usual long hikes due to previous miscarriages. Her ankles looked slimmer at 8 months than mine do after a day of sitting. She ate super healthy and fresh.
          Her primary indicator for obesity was that her boobs had suddenly gone from a perky B to a still pretty perky D.
          And instead of enjoying her A-grade pregnancy body, this poor woman was genuinely scared about being obese and therefore horrible.

          • EmbraceYourInnerCrone
            June 11, 2018 at 11:21 am #

            Ummmm, did she not realize that ones boobs going up a couple sizes is a normal (usually temporary) side affect of pregnancy?

          • AnnaPDE
            June 11, 2018 at 11:34 am #

            In theory she did, but then the squishy nature of larger boobs, plus their sudden increase in volume, apparently exceeded expectations by enough to count as legitimate steps towards getting morbidly obese. It’s not easy being crunchy .

          • EmbraceYourInnerCrone
            June 13, 2018 at 7:50 am #

            My problem was my feet, no one told me that my feet would spread in the last trimester. And my feet ended up a half size bigger than before I was pregnant….

          • lsn
            June 15, 2018 at 8:14 am #

            Mine too! Except it was more like a full size… I have been replacing shoes ever since.

          • MaineJen
            June 15, 2018 at 8:42 am #

            Yep, my feet got a whole size bigger during my 2nd pregnancy and never went back! Dang.

          • EmbraceYourInnerCrone
            June 15, 2018 at 10:04 am #

            One of the books I found later would have been great to have when I was pregnant, it was called The Girlfriends guide to Pregnancy, (or things your doctor will never tell you). Its probably a bit dated as it was written in about 1999, but still helpful.

          • Kelly
            June 11, 2018 at 9:13 pm #

            I wish it were temporary for all. Mine went from a D to an H in pregnancy and only went down to a G. I was so disappointed.

          • Gæst
            June 13, 2018 at 3:42 am #

            Yeah, I wish mine had gone back to their smaller size – 34 GG is a difficult bra size to shop for.

          • Who?
            June 13, 2018 at 5:48 am #

            I went from a AA before pregnancy to a B after I finished breastfeeding the second time, and stayed there quite happily until I went on HRT, when I blossomed to an E cup. The rest of me is the same size as in my early thirties ie more than 20 years ago.

            It plays hell with my BMI and costs me a fortune in bras, but in the scheme of things it’s not the worst side effect of menopause.

          • Kelly
            June 13, 2018 at 11:34 am #

            I have to go to a specialty shops because I am a 30 G OR H depending if I’m pregnant or not. I will be getting a reduction when I am done having kids.

          • Gæst
            June 13, 2018 at 11:42 am #

            I do as well, but there aren’t many around so I end up ordering from the internet, which is annoying because you really need to try them on. I wish a reduction was possible for me.

          • Kelly
            June 18, 2018 at 2:54 pm #

            We are definitely going to have to save up for it and I hope that my insurance will cover it since I am a 30 G when not pregnant.

    • demodocus
      June 8, 2018 at 11:55 am #

      The only time my boy was was higher in weight than height, he turned out to be a week from his growth spurt. (He’s only 4, but so far is mostly on the beanpole route.) Another time, at the tail end of a growth spurt, he looked pretty underweight by the charts. I swear you can -watch- infants grow in their sleep.

      • Who?
        June 8, 2018 at 6:56 pm #

        Wait until they are teenagers. I swear my kids were taller after the weekends, when they slept a bit more than usual, and at the end of even a week’s holiday when they could eat what they wanted when they wanted (both notoriously hated ‘packed lunches’) and sleep as much as they liked.

        My son gained 15kg in 12 months from age 14 years 6 months to 15 years 6 months.

        • demodocus
          June 8, 2018 at 9:55 pm #

          I don’t doubt, lol.

        • BeatriceC
          June 8, 2018 at 10:30 pm #

          My middle kid shot up nearly a foot in less than a year. I swear watching him grow was a spectator sport. It got to the point where I was only buying him shorts because I could get at least 2-3 months out of them.

          • Who?
            June 8, 2018 at 11:35 pm #

            Excellent plan. My boy wore long pants to school, I was taking them down an inch every month or so. He didn’t grow much around the middle or chest, though his shoulders did get broader over the time.

        • momofone
          June 11, 2018 at 12:11 pm #

          My 11-yr-old was a tiny little peanut of a baby, but now, in the throes of growth spurts, nothing is safe–last night I prepared my lunch for today, and when I went in to put in my lunch bag and stick it in the fridge, he’d eaten it. I have a feeling by the end of summer he’s going to be a few inches taller.

    • StephanieJR
      June 9, 2018 at 9:46 am #

      Exactly! I don’t know much about babies, but I do know that they, y’know, GROW. They increase in size so quickly, how can an infant be considered overweight? After a certain age it might be a concern, but babies are squishy puddles of fat that need to be fed.

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