In today’s New York Times Magazine, I was disturbed to see a major misrepresentation. The article described a social movement of fat-acceptance activists. Robin Marantz Henig made points with which I agreed: some people can be fat and healthy; we should emphasize intuitive eating; and the emotional and physical benefits of exercise are often under-emphasized. However, Henig quotes Dr. Leibel of Columbia University Medical Center who states that severely obese people have underlying genetic differences from the rest of the population, implying that they should not be blamed for their weight.
First of all, the Dr. Leibel is referring to the severely obese, while Henig's article focuses on all overweight people. The general breakdown is that people with a body mass index (BMI) over 25 are overweight; BMIs over 30 are obese; and BMIs over 35 are severely obese. For Henig to treat someone with a BMI of 27 the same as someone with a BMI of 37 is unfair, and likely goes beyond what Dr. Leibel was trying to say.
Second of all, Henig makes no mention of the fact that some genes can be determined by the fetal environment. Maybe we cannot blame overweight people for being overweight, but what if their weight was affected by what their mother ate while pregnant. A growing body of evidence points to the fetal environment as a crucial player in the fight against chronic diseases of adulthood.
Most parents-to-be are focused on having a healthy baby, but few think about making sure that that baby grows up to be a healthy adult. Thoughts about their baby’s long-term health tend to surface only after the birth, with many conversations focused on breastfeeding, first foods, healthy snacks, and raising healthy eaters. However, as the “developmental-origins of human disease" hypothesis  continues to gain momentum, and earn research money, pregnancy goals may have to change.
The basis for the developmental-origins hypothesis is that the fetus has “developmental plasticity,” the ability to develop in various ways depending on the fetal environment. Some of you might be thinking like Dr. Leibel: Don’t genes determine the future health of the fetus? Well, yes. But where do the genes come from? Nutritional genomics studies indicate that the genes fetuses receive from their parents can be regulated by nutrients the fetus receives during pregnancy.
Sometimes these changes can be a good way for the body to adapt to its environment. For example, the gene variant that regulates hemochromatosis (excessive iron absorption) may have been originally enabled in a low-iron environment, when the gene allowed the body to adapt to poor nutrition. But that same gene causes iron-overload in an adequate-iron environment if the gene is passed to future generations. Sometimes the gene is passed to the next generation, sometimes it is not. A more well known example involves folic acid. There are 2 genes that increase the risk for neural tube defects in an environment that is deficient in folic acid. This is why women are urged to take folic acid supplements; so that if they have those genes, the rich-folic acid environment will down-regulate the gene expression. Since the neural groove is formed during the 3rd gestational week, it is important to start taking folic acid prior to the pregnancy.
The fact that genes can be up and down regulated - that is, expressed or not - is proof that organisms evolve over time to adapt to their environments. But what if they adapt in ways which are not helpful? A fetus may respond to a limited nutritional environment by changing their metabolism, hormone production, and the way their tissues respond to hormones. These changes in tissue and organ development can result in disturbed responses later in life.
There are many example of how this plays out in real life. If we were to graph these variations based on birth weight, we see a “U” shape: infants who are born with low or high birth weight are more susceptible to these changes than infants born at average birth weights. In addition, fetal under-nutrition and over-nutrition is more likely to facilitate disease. This is no coincidence. Under and over nutrition are more likely to produce low and high birth weights.
What does all of this mean for children? Here are some examples from human and animal studies.
Human studies: * Smaller size at birth, followed by rapid childhood growth, is associated with heart disease, stroke, diabetes, obesity, metabolic syndrome and osteoporosis. * Over-nutrition during fetal growth or infancy (i.e. formula feeding) is associated with obesity, diabetes, and osteoporosis. * Imbalances in B12 and folic acid may lead to insulin resistance. * Chronic fetal anemia may lead to heart disease. * Early prenatal famine is associated with schizophrenia.
Animal studies: * A low protein diet in the pre-implantation period (0-4 days) is associated with altered organ development, low birth weight, increased postnatal growth, and adult hypertension. * Excess glucocorticoids (steroid medication) during pregnancy leads to increased sensitivity to postnatal stress, and increased hypertension. The same result can also be caused by postnatal stress, defined as reduced grooming/licking by animal mothers.
What you can do to ensure a positive fetal environment: Have a healthy weight gain during pregnancy. Women who have a normal weight before getting pregnant should gain 25 to 35 pounds. Women who are underweight before pregnancy should gain 28 to 40 pounds. And women who are overweight should gain 15 to 25 pounds. Obese women should gain at least 15 pounds. Eat fish high in omega-3 fatty acids and low in mercury or take a supplement. And, of course, eat a healthy diet before and during pregnancy to ensure a healthy balance of nutrients. Don’t know what a healthy pregnancy diet is? Sign us for my RSS feed to continue readings my posts.
Feed your children fish too. There is some evidence that omega-3 fatty acids can reverse some of the negative effects of poor nutrition during pregnancy.
I would love to know your thoughts, feel free to comment!
A few journal references for further research can be found here, here, here, and here (full-text subscriptions required).
 The Developmental Origins of Human Disease Hypothesis is also known as the Fetal Origins of Adult Disease Hypothesis and the Barker Hypothesis