Junkfood Science: <i>Junkfood Science exclusive:</i> A time for joy and nurturing

December 08, 2006

Junkfood Science exclusive: A time for joy and nurturing

Pregnancy and new motherhood is one of the most stressful and anxious times for most women as they worry for themselves and the innocent lives in their care. This concern means they’re especially vulnerable to becoming alarmed by health scares and to react out of fear, with potentially harmful outcomes. So it is especially imperative that the health information they receive is well-grounded, credible and helpful.

When the headlining story — which appeared virtually verbatim in media across our country and around the world — told women they were putting their pregnancies and unborn babies at risk if they didn’t lose all of their pregnancy weight and begin their next pregnancies at “healthy” weights; weight loss admonitions began instantly. In fact, the researchers whose study this news story was based upon told media that their “striking findings” provided “the evidence that overweight or obese women who plan to become pregnant should lose weight.”

Even a modest increase of 7 pounds, the public was told, could raise a woman’s risk for pregnancy-related complications, such as gestational diabetes by 30% and pregnancy hypertension 40%. But they delivered even more frightening news, warning women that “gaining 3 or more units of BMI (body mass index) raises the risk of a stillbirth by 63%, pre-eclampsia and gestational hypertension by 78% and 76%, and could double her risks for gestational diabetes.”

“These are staggering numbers,” Daniel Herron was quoted as saying. Women should not wait for later research before changing their behavior and losing weight between pregnancies, he added. [Not a single reporter revealed that Herron is not simply an “associate professor of surgery at Mount Sinai Hospital” as they reported. He is Chief of Bariatric Surgery with Mount Sinai’s Program for Surgical Weight Loss, as well as on the Public/Professional Education Committee of the American Society for Bariatric Surgery. Readily-known interests, in promoting fears of obesity and the need for weight loss, the media didn’t disclose.]

Also quoted in the media reports was a reproductive health specialist with the World Health Organization who said: “This is the first study to provide...the necessary evidence to show a causal relationship between obesity and adverse outcomes.”

What is passing for evidence and sound interpretations by health authorities is, in fact, what is most staggering.

What did the study show?

This study was conducted by Eduardo Villamor, M.D., of Harvard School of Public Health and Sven Cnattingius, M.D., of the Karolinska Institute in Stockholm. They sorted through data from the medical records of 151,025 Swedish women who had had their first and second babies during 1992-2001. It was a “case-controlled” study, looking retrospectively through histories trying to find correlations between BMIs and pregnancy complications. The researchers applied statistical modeling of the data to create the odds ratios they reported.

To make any sense of their findings, we must first understand what an odds ratio actually means. See side bar: Odds Ratios.

The first thing you’ve probably noticed is that none of those scary-sounding percentages reported in this study are credible for such statistically-derived findings. We could leave it right there, but a few of the “nonfindings” may further help lessen undue concerns about weight and reveal a few holes no one’s talking about.

These researchers found that risks for pregnancy complications — pre-eclampsia, gestational diabetes, stillbirths and large for gestational age babies — were the same whether the women were fat or not. Being fat didn’t matter.

So, it seems, some statistical maneuvers were necessary to find something to pin on weight.

Most of the women gained on average just over half a BMI unit (0.3 to 1.7) between pregnancies. So women gaining 3 or more BMI units were uncommon and those “staggering” risks we heard for them may have been more reflective of linear projections in the researchers’ mathematical model. At the very least, they greatly inflate the risks for most women

Behind the scenes: ignored factors

To calculate the difference between what the women weighed at the beginnings of their first and second pregnancies, the authors used the weights recorded at their first prenatal visits. However, how far along the women were when they first went to the doctor was unknown! Nor did they have any information on illness or other things that might have affected the women’s weights before seeking prenatal care, or during or after their pregnancies. This is a huge flaw. It alone could easily explain their findings, especially given the minor 7 pound weight differences they’re claiming mean something.

The timing of the first prenatal visit, and a woman’s condition at that initial exam and throughout her pregnancy, could easily be a marker for socioeconomic factors. For instance, women who are poor, minority, with fewer resources, lesser educated, young single mothers, having unplanned pregnancies, or those with substance abuse problems are more likely to delay prenatal care and be further along and therefore, heavier by the time they are first seen by a doctor. According to the March of Dimes, most women gain about 2-4 pounds during the first trimester and about a pound a week for the remainder of a pregnancy.

In fact, socioeconomic factors are evident in the researchers own notes: “Weight gain between pregnancies decreased with age, education...[and] women of Nordic origin." Yet these researchers failed to acknowledge or even consider socioeconomic factors, which are well-documented to be significant in health outcomes. Instead, they pointed to weight.

That is especially puzzling since Dr. Cnattingius’ own research on Swedish mothers published just a few years ago in the International Journal of Epidemiology concluded that it was low socioeconomic status that increased the risk for stillbirth, and none of the other factors they examined were associated with these poor outcomes, including prenatal care, reproductive history, maternal diseases or pregnancy-related health problems such as pre-eclampsia or hypertension.

Even the U.S. Centers for Disease Control and Prevention’s Pregnancy Mortality Surveillance System reports disparities in pregnancy-related mortality in the US., continuing since 1940. Blacks, for example, are four times more likely to die from pregnancy-related causes than are white women. Black women also appear to hold onto their pregnancy weight three times more than white women, as has been reported in the American Journal of Clinical Nutrition.

The higher weights at the beginning of the second pregnancies can also reflect more weight gained during the first pregnancy. Excessive weight gain is a classic symptom of pre-eclampsia (also called toxemia), along with high blood pressure and protein in the urine. Good prenatal care is important to avoid complications. While the causes for pre-eclampsia are unknown and there are no known ways to prevent it, 85% of cases occur during the first pregnancy and it is twice as common in Blacks and four times more common in women with a family history. Yet the researchers didn’t acknowledge these potentially significant factors and untold others. Instead, they pointed to weight.

Finally, like the WHO health expert quoted in the news, they made the most egregious error of all: believing correlations can ever show causation. The researchers said the evidence is compelling and strengthens the argument for causality between weight gain and harm to mother and baby.

It’s that silly “killing turkeys causes winter” argument. If it weren’t for the fact that everyone believes weight is to blame for everything, the fallacy would be more apparent.

They then proceeded to skip in reverse and say that these findings “provide robust epidemiological evidence for advocating weight loss.”

Except this statistical report was unable to even find tangible correlations, let alone any evidence for advocating a preventive treatment. Unless you believe that eating tofu-turkey can lead to eternal summer.

Commentary: For most of human history, fat has been life-sustaining — seen as security against scarcity, and a desirable sign of fertility and ability to bear and nurture children. Pregnancy and childbirth is also a natural time when many women gain weight, and by middle-age most women have about 38% body fat. This has long been recognized, hence, weight recommendation charts were according to age. Fat is necessary for the production of many hormones such as those involved in calcium metabolism, normal growth and development, and fertility. Girls need body fat to begin normal puberty and women to menstruate, get pregnant and carry babies to term. Given the protective, fertility, immunological and nurturing benefits of fat stores, it is not surprising that there is no evidence that midlife weight gain is harmful to healthy women. In fact, most evidence has long shown it to be beneficial. But the unintended consequences of unsound scare marketing about weight gain are very real, and very heartbreaking. Women going into a pregnancy underweight, nutritionally compromised (by poverty, dieting or bariatric surgery), or afraid to gain weight during the pregnancy can compromise their baby’s health and their own.

© Szwarc 2006

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