There are a myriad of benefits attributed to breastfeeding; some which are backed by stronger science than others. Since all of these studies are observational and can’t control for every conceivable confounder, we need to look at “reviews” or meta-studies to see if the same finding is being confirmed in a variety of good-quality studies. For certain benefits – like a decrease in ear infections and gastrointestinal infections – we’ve seen enough evidence to justify touting these advantages. So I honestly have no problem with people claiming that breastfeeding protects against these two childhood health threats.
But one of the least definitive claims in breastfeeding science is that breastfeeding protects against childhood obesity – or, more to the point, that formula feeding increases the chance of obesity. Yet this seems to be the cause du jour of Michelle Obama’s plan to fight childhood obesity. Politics Daily
Looking ahead to what she will do in the second year of “Let’s Move,” Mrs. Obama said: “We also want to focus on the important touch points in a child’s life. And what we’re learning now is that early intervention is key. Breastfeeding. Kids who are breastfed longer have a lower tendency to be obese.
Breastfeeding rates are low among African-American mothers compared to other racial and ethnic groups, according to the Centers for Disease Control and Prevention, and Mrs. Obama took note of this when she addressed the Congressional Black Caucus Conference on Sept. 10.
“And because it’s important to prevent obesity early, we’re also working to promote breastfeeding, especially in the black community — where 40 percent of our babies never get breastfed at all, even in the first weeks of life, and we know that babies that are breastfed are less likely to be obese as children,” she said.
Really, Michelle? We know that? (And guys, before anyone starts freaking out on me, I’m an independent. I hate politics. This is not about politics to me, it’s about bad science.)
I’m not sure exactly what research Obama is referring to, but at least her administration’s Surgeon General is leaning on a 1997 AHRQ report for their recent “Call for Action on Breastfeeding”. Let’s see what that report actually says about the link between breastfeeding and obesity:
Obesity. Three meta-analyses of good and moderate methodological quality reported an association of breastfeeding and a reduction in the risk of obesity in adolescence and adult life compared with those who were not breastfed. One study reported the reduction in the risk of overweight/obesity in breastfeeders compared with non-breastfeeders was 24 percent (95% CI 14% to 33%); another study reported 7 percent (95% CI 1% to 12%). Both of these estimates took into account the role of potential confounders. Furthermore, they also showed that the magnitude of association decreased when more confounders were entered into the analyses. The third study used meta-regression and found a 4 percent reduction in the risk of being overweight in adult life for each additional month of breastfeeding in infancy. Overall, there is an association between a history of breastfeeding and a reduction in the risk of being overweight or obese in adolescence and adult life.One should be cautious in interpreting all these associations because of the possibility of residual confounding.
Source: Breastfeeding and Maternal and Infant Health Outcomes in Developed Countries. Evidence Report/Technology Assessment No. 153, AHRQ Publication No. 07-E007. Agency for Healthcare Research and Quality. April 2007.
In plain speak, this report states that while a few studies have shown an advantage (and a small one, at that – a 4 percent reduction in risk is pretty puny, and probably not worth basing a whole campaign over) to breastfeeding when it comes to combating obesity, these studies have also been rife with confounding factors, and that the benefit is not entirely clear.
And guys, that is being GENEROUS. Let’s look at what some other studies have to say on this topic:
“As in the 1958 birth cohort,3 results from their offspring provide no support for a protective effect of breast feeding on obesity. In studies reporting a protective effect, it is weak and not always supported by a dose-response relation, which might be expected, at least up to a threshold duration. Any effect of breast feeding may be limited to a critical period or depend on other cofactors. Secular trends do not suggest a protective effect: in both Britain and the United States the incidence of breast feeding has increased since 1990, but so has obesity. Promoting breast feeding is important, but evidence for an important beneficial effect on obesity is still equivocal.”
“Most studies examining the effects of breastfeeding on later obesity have found an insignificant effect. Breastfeeding was positively associated with later body fatness in two studies. A protective effect of breastfeeding on childhood obesity was seen in four studies. An effect of breastfeeding on later obesity, if any, is probably weaker than genetic and other environmental factors. Also, an observed association between breastfeeding and later obesity does not prove causality. Controlling for confounders in an attempt to minimize the effects of differences between breastfeeding and formula-feeding mothers was done to a varying extent across studies. In several of the later studies, adjustment for confounders obliterated the effect of breastfeeding. Whether all the pertinent confounding factors have been measured and whether the differences between mothers who chose to breastfeed and mothers who chose to formula-feed have been controlled for adequately are always questionable… Although a highly provocative concept, the protective effect of breastfeeding on later obesity remains controversial.”
“According to David Barker, M.D., Ph.D., professor of clinical epidemiology at the University of Southampton, UK and professor of Cardiovascular in the Department of Medicine at the Oregon Health and Science University and one of the authors of the report, “A longer period of breastfeeding was associated with lower BMI (a measure for weight) at one year of age. This relationship disappeared by the age of 7 years.” Similarly, there was no significant difference in BMI at the age of 60 years associated with duration of breastfeeding….Another session presenter, Michael Kramer, M.D., pediatrician and perinatal epidemiologist at McGill University, reported findings from his breastfeeding promotion intervention trial that support Dr. Barker’s results..breastfeeding… did not reduce the development of obesity at 6.5 years of age.”
There are other studies which do find some positive correlations between breastfeeding and lower BMI, but even the most convincing of these state that the benefit is consistent, but small. (See “Breastfeeding and Childhood Obesity – A Systematic Review
“) I can’t wrap my mind around how large a gap there is between what science actually says about this and the dramatic claims the government is now legitimizing.
“Regardless of when they started eating solid foods, breastfed babies in the study had a one in 14 chance of being obese as preschoolers.
But the findings, published in the journal Pediatrics, were different among babies who were formula-fed from the beginning, or who stopped breastfeeding before they were 4 months old.Those babies had a one in four chance of being obese at age 3 if they started eating solid foods before they were 4 months old. If parents waited until between 4 and 5 months, the kids’ chances of being obese were one in 20.
The chance of being obese increased again if babies didn’t start eating solid foods until they were at least 6 months old, but there were too few of those babies for the authors to make a firm conclusion about the risk of waiting longer to feed a baby solid foods.”
Okay, I don’t know about you, but here’s what I glean from this Reuters article. Babies who are breastfed have a 1 in 14 chance of being obese no matter when they start solids. Formula fed babies who start solids between 4-6 months, as recommended by the AAP, and as is common practice in this country these days, have a 1 in 20 chance.
What’s lower, 1 in 14 or 1 in 20? I suck at math, but, umm….?
And yet, the remainder of this article goes into the same old shpiel about how most babies aren’t breastfed long enough, yadda yadda yadda.
I am all for promoting breastfeeding. I am glad that breastfeeding expenses can be used as a tax write off (although I’m aggravated that my expensive hypoallergenic formula doesn’t fall under the same category). But I am not a fan of misleading claims, especially when it comes to an issue this sensitive for so many women.
I’d also submit one last tibit, courtesy of MommaData’s
awesome Polly Palumbo:
“Some suggestion” is vague, but then again, so are most of the findings supporting this assertion that formula feeding increases the chance of obesity. What this suggests to me is that the science is far from clear on this issue, and saying we “know” that babies who are breastfed are less likely to be obese is one big fat lie.
I appreciate what Michelle is trying to do in supporting breastfeeding, but supporting it for the purpose of reducing obesity is misguided at best, and coercive at worst.