Poor nutrition in utero, heavy child tomorrow?

"In other fields where people study butterflies, turtles and frogs, they have known for a long time that fetal development is very plastic and that any type of stress in the environment can cause a different phenotype in the animal," Heindel says. "In humans, people thought it was just genetics. But humans are just like these other animals." Today, U.S. doctors are primarily concerned about excessive weight gain during pregnancy. That too appears to program a fetus for metabolic problems later in life.

Exposure to a high level of blood sugar or fat before birth can change the development of fat cells and the pathways in the brain that regulate appetite, says Beverly Muhlhausler, a researcher at the University of South Australia's Early Origins of Adult Health Laboratory and an authority on fetal diet and adult disease.

"What research is now showing is that consuming an excessive amount of high-fat, high-sugar foods during pregnancy can alter the development of the baby in such a way that predisposes that individual to becoming obese later in life," she says.

Scientists from Kaiser Permanente's Center for Health Research recently found that children of pregnant women untreated for high levels of blood sugar were 89% more likely to be overweight and 82% more likely to be obese by the time they were ages 5 to 7 compared with children born to women who had normal blood sugar levels during pregnancy. The study was published last month in Diabetes Care.

One of Muhlhausler's studies in sheep found that fat cells in fetal sheep whose mothers had been fed a high number of calories during late pregnancy produced natural substances that promoted fat storage.

Further, a mother's diet may also cause changes in the fetal brain that later influence appetite and food preference.

"These individuals are less able to switch off their appetite and stop eating even when they've consumed enough calories. And this also makes them more prone to weight gain," she says. A similar study in August in the British Journal of Nutrition found that pregnant rats fed a diet of processed junk food subsequently gave birth to baby rats that also preferred junk food.

"There is so much emphasis put on a child's eating habits at school, but research is telling us more and more that the pathway to obesity can start long before the child gets to school age," Muhlhausler says. "One of my dreams as a researcher is to be able to get the message out that what you eat during pregnancy has a huge impact on your child's development and long-term health prospects."