Preventing Obesity before Birth

As Americans' waistlines spread and obesity reaches epidemic proportions, a growing number of researchers are looking at the possible link between a woman's nutrition during pregnancy and a baby's risk of becoming overweight.

The importance of prenatal care has long been recognized. Now scientists interested in preventing obesity are exploring the relationship between maternal diet and fetal growth and children's chances for becoming overweight later in life.

Simon Langley-Evans, a professor of biological sciences at the University of Nottingham in England, was the lead researcher in a recent study that found that feeding mice a low-protein diet throughout gestation led to female offspring that were less likely to eat fatty foods. Varying the diet, though, changed the results.

“In the second experiment, we offered low-protein chow only during certain stages of gestation, ” Langley-Evans said, “and to our horror, we found that the opposite thing happened,” with the offspring actually being more likely to choose fatty foods and become overweight than the mice in the control group.

But how does a female mouse's diet affect her offspring in the first place? Langley-Evans thinks that the low-protein diet affected the development of the hypothalamus in the mouse fetus. The hypothalamus controls the body's temperature, appetite and sleep cycle and regulates the metabolism.

In humans, the hypothalamus begins forming during the first month of pregnancy and is well developed by the end of the first trimester. Langley-Evans hopes that the connection between diet and the development of the hypothalamus in mice might lead to new information about the importance of diet for humans during pregnancy and lead to better education on maternal nutrition.

“Certainly in the U.K. the kind of advice women get about pregnancy isn't very detailed. They tell you not to eat liver, to take folic acid," he said. "Maybe they could come up with something more detailed.”

Prenatal nutrition can help “switch on” genetic obesity triggers, according to Eric Ravussin, a researcher at the Pennington Biomedical Research Center in Baton Rouge, La. The health of mothers "doesn't change [the babies'] genes, but it changes the expression of their genes,” Ravussin said.

Ravussin said that twins have nearly identical genetic make-ups, but because their conditions in the womb vary, the expression of their genes can be different. One fetus may have gotten more of one nutrient, while another received less. As a result, they may form differently and have different risks of disease. Studying those prenatal influences on genetic expressions, Ravussin said, is part of an expanding frontier in medical research. “It's a very new science called epigenetics,” Ravussin said, “and it's going to be in more and more studies.”

Although most research into obesity and epigenetics has been conducted in the United Kingdom, Canada and New Zealand, the United States is beginning to catch up. The Pennington center received a $5.5 million federal grant to establish a clinical nutrition research unit, which Ravussin will direct. Its work will focus on the prenatal causes of obesity and diseases.

While maternal diet and genetics play a crucial role, what happens to a child after it leaves the womb may be more important, said Marlene Schwartz, co-director of the Yale Center for Weight and Eating Disorders. Genes aren't necessarily destiny, said Schwartz, who studies childhood obesity. "Some people you'll put anywhere and they won't become obese, some the other way around," she said. "But most people fall in the middle.”

She believes that genes and prenatal nutrition may program people to become obese. But environment--diet and exercise, for example--are the deciding factors.

Langley-Evans doesn't discount the importance of environmental factors in children's development, but his research suggests that what happens in the womb is critical. As he has seen in his research in mice, if a mother eats right and exercises during pregnancy, her offspring may be just a little less likely to crave fatty foods and to store fat.

“Obesity is very complex,” Ravussin said. “You give access to mice to an exercise wheel, and you have some runners and some couch potatoes. And we don't know why.”

-- Jennifer Phillips - Columbia News Service