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Ultrasound at 18 weeks (Globe files/Globe files)
Ultrasound at 18 weeks (Globe files/Globe files)

Part two of two

A new prime suspect behind the global upsurge in obesity and diabetes: the womb Add to ...

Indeed, the International Federation of Diabetes predicts that in two decades the number of diabetics worldwide will jump by more than half, to 438 million from 285 million, with three-quarters of those affected in low- and middle-income countries.

In many ways, Prof. Benyshek says, North America's native populations, hammered by diabetes for 50 years, "have been like canaries in a coal mine." They had "decades of really severe economic conditions and deprivation in the first part of the 20th century."

In the mid-1980s, as Prof. Barker worked on his theory, Heather Dean, a pediatric endocrinologist at the Children's Hospital in Winnipeg, began to see aboriginal children with type 2 diabetes. "Oh, oh," she thought. "What is this?"

Children, it was believed, almost always develop type 1 diabetes, where the pancreas simply stops making the insulin needed to turn blood sugar into the fuel that powers the body. Type 2 diabetes was supposed to be an adult's disease - the result of insulin resistance, or a pancreas unable to keep up with the insulin demands of an older, and often, larger body.

Those first children were obese, Dr. Dean says, but obese children in the past always managed,

with their young pancreases, to produce enough insulin. "It shouldn't happen that a 12- or 13-year-old has type 2 diabetes and can't overcome it."

Yet the caseload multiplied - shooting up from a handful a year to more than 70 last year (equal to the number of new patients at her clinic with type 1 diabetes). Meanwhile, a lack of healthy food and exercise cannot fully explain it, she says - not all the children are obese, and a few are as young as 6.

"Something is really affecting, and very quickly accelerating, a child's inability to withstand the factors that lead to disease … ," says Dr. Dean, an assistant dean of medicine at the University of Manitoba. "You have to ask, 'Why is this happening?'"

As she and her colleagues investigated further, they discovered that a child born to a woman with type 2 diabetes before becoming pregnant had a dramatically higher risk of developing the disease in childhood - more than 14 times higher.

They are also finding that nearly every new patient has a mother, grandmother and great-grandmother who also had type 2 diabetes, and each successive generation developed the disease at a younger age.

"It's happened so quickly, it has to suggest an epigenetic phenomenon," she says. Without environmental influences, "genes don't change that quickly."

Skeptics cling to their genes

Not everyone finds the origins theory as compelling. Jeffrey Friedman, a leading obesity researcher at Rockefeller University in New York, feels that it "may be relevant in parts of India and China," but is not powerful enough to explain the story everywhere. Dr. Friedman, who has for years been searching for thrifty genes to explain the sudden rise of obesity on the Pacific island of Kosrae, believes that "evolutionary forces" have the more significant impact on the genes that mould a person's predisposition to be fat or thin.

Jared Diamond, the well-known author and geography professor at the University of California in Los Angeles, also doubts that prenatal conditions, more than DNA, predict future disease risk. In a 2003 paper, he cited studies showing that when one identical twin develops diabetes, the chances are nearly 100 per cent that the disease will strike the other twin too. But the odds are only 20 per cent for fraternal twins, who share the same womb, but different DNA, "suggesting that factors in the uterus play a ... minor role," he wrote.

Prof. Benyshek, however, says that, while there may be susceptibility genes for diabetes, the seeds of today's epidemic among aboriginal people were sown just a few generations ago. In the 1990s, he was part of an unsuccessful attempt to find a "thrifty gene" in the native people of Arizona, particularly the Pima Indians, who have the world's highest diabetes rate.

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