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A Response to the New Breastfeeding and Obesity Study

Looking for The Lactivist? She's retired. But you CAN still find Jen blogging. These days, she's runs A Flexible Life. Join her for life, recipes, projects and the occasional rant.

Wednesday, April 25, 2007

I've already got a pretty lengthy post up talking about the new study that claims breastfeeding has no impact on future obesity. In that post, I asked for some feedback from people that have a better understanding of studies.

Always one to lend a hand, Ohio Breastfeeding Coalition member (and epidemiologist) Jessica Lietz has graciously put together the following response. I thought my readers might find it interesting...

A study, "A longitudinal study of infant feeding and obesity throughout life course" by KB Michels, WC Willett, BI Graubard, RL Vaidya, MM Cantwell, LB Sansbury and MR Forman, was advance-released online by the International Journal of Obesity (International Journal of Obesity (2007) 1–8), claims that there is no association between breastfeeding and risk of obesity in adulthood.

Please hold on a minute while I put my epidemiologist hat on, and get my claws ready to tear this apart.

Okay, ready.

My preferred route of attack is with the methods section, as that is where the meat of the study is. The first concern I have is that the participants of the study are mainly Caucasian, as stated: "Participants are predominantly Caucasian white". The study provides no further background on the race or ethnicity of the participants. Many studies, such as "The Decision to Breastfeed in the United States: Does Race Matter?" (Pediatrics, Vol. 108 No. 2 August 2001, pp. 291-296) state that race is an important predictor of breastfeeding.

Second, they did not determine the SES (socio-economic status) of the study participants as infants or as adults in the way that most studies do (as percent of the Federal Poverty Level, which is based on family size and household income). A family of two earning $30,000 is much different from a family of 6 living on the same amount in the same locale. Moreover, many studies have shown a direct correlation between socio-economic status (SES) and duration of breastfeeding (examples: Effects of socioeconomic status on breastfeeding duration in mothers of preterm and term infants, from The European Journal of Public Health Advance Access published online on March 28, 2007; and Socioeconomic Status and Breastfeeding
Initiation Among California Mothers from http://www.publichealthreports.org/userfiles/121_1/121051.pdf).

In addition, in the tables of demographics, more than 28% of survey participants reported household incomes of $100,000 or more. This is not representative of the United States population.

The authors asked about the SES of the nurses' households, but not the households the nurses grew up in. I don't know about you, but most of my habits were formed well before I got married, and many habits- dietary and physical activity- are related to SES. For example, my mom had a factory laborer job and so did my dad and both have high school educations (less likely to breastfeed) and were poor enough to get WIC when I was a child (again, less likely to BF). It is basically impossible to breastfeed (or pump) when you stand on an assembly line all day.

They both had to work to pay for their rent, car, etc. It is a lot easier to breastfeed (and pump) when you have a white collar job. Here I am, 28 years old, with a Masters (husband has a BS) and we are not "poor". So asking my current SES would give you a much different picture than the SES I grew up in. I would also like to know why they recorded the nurses' husbands' education levels rather than those of the nurses (because we all know that the hubbies bring home the bacon, right?). As a side note, they did not use the same education level intervals for the nurses' parents as they did for the nurses' husbands.

Okay, so I don't like who they included in the study. So what? Let me dig in a little deeper. I also have some issues with what they did not ask the study participants. Participants were not asked to report the obesity status of immediate family members. Also, the nurses' mothers were not asked why they ceased breastfeeding. Perhaps there are differences in those who stopped after one week versus those who breastfed more than 6 months, such as what type of birth attendant the mother had (ob/gyn, family practice physician, or midwife), where the birth was at (home, hospital, or somewhere else), whether the mother had complications (c-section, mastitis, illness in baby, illness in mother), or other reasons (told to stop by doctor, didn't like it, hurt, took too much time, didn't get needed help).

Next up: how they asked what they asked. First, they had the nurses rate, based on pictures, what their body shape was. I don't know about the rest of you, but I know I have a warped image of what I look like (thanks to our American culture), and most women I know do as well. I'm sure I would choose a different image for myself than my husband or mother would choose for me.

And to ask me what shape I was at age 5 or 10?

I don't even remember anything from when I was 5 years old, and all I remember about being 10 was that my Grandpa died (or was that when I was 9? Or 11?). The authors themselves admit that the figures are "imperfect".

Moreover, "body fatness" based on appearance has NOTHING to do with BMI. Someone could be heavy in pounds due to muscles and therefore have a high BMI, but not be a "9" from the figures. And, few participants said they were a level 5 at ages 5 or 10. In other words, none of them wanted to state that they were "fat".

Second, the way they asked the duration of breastfeeding does not make any sense. They did not even use the same intervals for 'ever breastfed' and 'exclusively breastfed'. And can you tell me how a person could possibly be in the "exclusively breastfed" category when the duration of breastfeeding was <1 week?

What else did that baby eat for the rest of its infancy?

The authors state "women who were breastfed for more than 9 months had a risk of becoming overweight or obese similar to that of women who were breastfed for less than 1 week or exclusively bottle-fed"; however, these were not the exclusively breastfed babies- just the "ever" breastfed. This means that the baby could have been nursed once a day and had 11 formula feedings.

And finally, their results were "null", meaning no effect. Normally those studies are rarely even published, because who wants to read an article about a lack of causation? We all want to read a cause-and-effect article (smoking causes lung cancer, pollution causes asthma, hormones do (do not, do, do not...) cause heart attacks (breast cancer, osteoperosis...).

For future activity: someone needs to look into the funding sources for the authors and their departments. I wonder, perchance, if any of the funding comes from anyone such as my friends a few blocks from here, at the big factory that makes baby formula?


  1. Anonymous Rachel | 1:13 PM |  

    We get it, studies are imperfect. I don't get why you and some of your reader's are threatened by the possibility that breastfeeding does not have a noticeable effect on obesity. Why the need to rip apart the study? To get published, even the best scientific magazines love provocative claims/studies.

    There are benefits to breastfeeding and I do think more people should give it a try (I did and I love it). I didn't breastfeed because I thought it would be a cure-all and make my daughter skinny for the rest of her life. If there's a chance that could be a benefit, great! If not, there are other ways I can mother her to promote a healthy weight.

  2. Blogger Judy | 1:32 PM |  

    I'm not threatened :)

  3. Blogger Damien McKenna | 1:42 PM |  

    If you are unable to properly digest food your body can and (probably) usually will treat it differently than a properly working digestive system. Babies are designed to consume breastmilk until they're able to ask for a bar-b-que'd chicken with side salad, so feeding them breastmilk will make their digestive systems as healthy as they can be. Formula, on the other hand, is a rough approximation of breastmilk that can never be anywhere near 100% the same, so it is missing a lot of the micronutrients, antibodies, etc that make it easier for the baby's stomach to digest. It has been suggested that one single bottle of formula can affect a baby's digestive system for several weeks, imagine what long-term usage would do?

    It's like comparing a perfectly made meal from a $100-a-plate restaurant vs McDonalds, the two are in completely different worlds and should be considered as such.


  4. Blogger Jennifer | 1:45 PM |  

    Rachel, the issue here isn't that this study might be wrong or might be right, it's that it coincides with news that formula companies are working on a new componant that they claim will keep babies from becoming obese as adults.

    In other words, this study seeks to say "breastfeeding doesn't do this" and then hey, the formula companies can say "but our formula does!"

    Otherwise, I don't think you'd hear near the outcry against it.

    And yes, studies are imperfect, but badly flawed studies should NOT be touted as the gospel truth on any and every media source out there.

  5. Blogger Nevanna | 2:12 PM |  

    I have a general problem with badly done studies. They creep up all over the news, but are taken as fact because a "study" can be sited.

  6. Blogger Damien McKenna | 3:04 PM |  

    Nevanna, I hear you there. So are you all making sure to get your sons circumcised to prevent them from getting AIDS? (BTW I've got a longer write-up I need to post on that topic..)


  7. Anonymous Marica | 3:08 PM |  

    Oh my gosh, formula companies are working on a componant to keep babies from becoming obese as adults?! That is the most ridiculous thing I have heard..however, I can totally see where that would sell in America, what a disgrace! When Anna Nicole died her nanny said on an interview that A.N. wouldn't allow the baby to eat a lot so she wouldn't get fat. The formula companies really know how to go after the money of the vain.

    Great breakdown of the study, thanks!

  8. Blogger Jennifer | 3:09 PM |  

    Damien, let me know when that's up.

    I've not covered the topic here, but as someone that did a LOT of research and decided to leave my son intact, I'd love to cover it at some point.

  9. Blogger Nevanna | 3:59 PM |  

    Glad I'm not the only one--we also left our little boy intact. I was actually asked fairly frequently while we were in the hospital if I planned on having it done. The thought just made me hurt, thinking of that kind of pain for a little newborn.

    Anyway, we both felt it was for an individual to decide as an adult. If he grows up and wants it done, fine.

    Sorry for the hijack. :)

  10. Blogger Damien McKenna | 7:50 PM |  

    (not meaning to hijack the thread, sorry Jennifer..)
    I threw in the comment on the MGM (male genital mutilation) as it is another current hot topic being steamrolled through the media as The Latest & Greatest Thing. And, like Jennifer has said, if you take a sampling of the media coverage you'd be led to believe that it was the right thing to do. Glad to see you ladies (and therefore husbands/SOs) taking the effort to become informed on the topic and not led by the nose while watching your newborn sons scream as they're being cut.

  11. Blogger Jennifer | 5:16 AM |  


    I just want to throw a caution out there that I'm not a fan of the loaded terminology used by the "intactivist" crowd. Quite honestly, I see comments like the ones you made as being no different from the pro-breastfeeding folks that trash formula feeding moms.

    While I firmly believe in leaving baby boys intact, I also firmly believe that "good parents" circ.

    By that I don't mean they are good parents BECAUSE they circ, I simply mean that people who are good parents often make the choice to circ. Sometimes it's because they haven't researched, sometimes it's cultural pressure, sometimes it's just done by force of habit because they think everyone does it.

    Therefore, while I respect your passion on the subject, I'd point out that any debate or posts that I have on the subject here will focus on educating and undertanding and not on accusations or name calling.

    You're not going to win anyone over by telling them how they mutilated their sons genitals. Especially if you are talking to the mom of a circ'ed son that will have more boys in the future.

    I know several families that made the decision to leave a son intact after having circed a prior son. Believe me, they weren't convinced by the people telling them how horrible they were for having done it the first time.

    I doubt you were aiming your comments at anyone specific, but you need to remember that anyone that reads your comments and that is the parent of a circ'ed child is going to take it very, VERY personally.

  12. Blogger Damien McKenna | 1:48 PM |  

    Jennifer: point taken.

  13. Blogger Jennifer | 1:54 PM |  


    Just to note, I hope you know that I meant that in a nice way and not in a scolding or mean or antagonistic way.

    Emotional undertones don't carry well in text, so I just want to be clear that I was writing what I did in order to be "helpful" and not in order to "scold."


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