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Low-Fat Diet Alone Reversed Type 2 Diabetes in Mice

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Duke Health News 919-660-1306

DURHAM, N.C. –- Researchers at Duke University Medical
Center have shown they can reverse type 2 diabetes in mice
simply by feeding them a very low-fat diet, and they believe
the same potential exists in humans.

While doctors have long known that weight loss can control
diabetes, the new research is the first scientific study to
show that type 2 diabetes can be completely reversed in animals
by lowering dietary fat, said Dr. Richard Surwit, professor and
vice chairman in the department of psychiatry at Duke.
Moreover, the findings suggest that reducing fat, not just
weight, is a primary mechanism behind the reversal, Surwit
said.

More than 14 million Americans have type 2 or
non-insulin-dependent diabetes mellitus in which abnormally
high blood sugar levels cause severe tissue damage. It is the
leading cause of blindness in the country and causes kidney
failure as well as irreparable nerve damage. Results of the
study, funded by the National Institute of Mental Health, are
published in the September issue of Metabolism.

The research findings suggest that, while genetics determine
which animals are at risk for developing diabetes, dietary
changes can compensate for the genetic predisposition, Surwit
said. If the same were proven true in humans, the potential for
preventing the disease could be huge, he said.

"Certainly, there is evidence from the more radical diet
programs like Pritikin or the Duke Rice Diet showing that
reducing fat intake can control diabetes, but the evidence has
all been anecdotal, and it hasn't illuminated the specific
mechanism behind the improvement," he said. "Our animal
research shows that, if you dramatically reduce the dietary
fat, you can reverse the problem."

In the study of a genetic strain of diabetes-prone mice, the
researchers found that cutting fat from 40 percent to 10
percent of their total caloric intake caused complete reversal
of their diabetes, regardless of what stage in life the mice
began the low-fat diet. And while the mice lost weight, the
researchers found that weight loss alone could not account for
the reversal, Surwit said.

That's because their insulin and glucose (blood sugar)
levels began to decrease before their weight did, suggesting
that fat reduction acts on insulin and glucose levels
independent of weight loss.

"We have known that animals can develop diabetes before they
develop obesity, so it stood to reason that animals could begin
to reverse their diabetes before they lost weight," said Dr.
Mark Feinglos, professor of endocrinology at Duke. "Weight-loss
and nutrition certainly are connected, but they are not
inseparable."

Feinglos emphasized that foods high in fat, not in sugar,
are responsible for the onset of diabetes in the mice. In fact,
sugar had no effect on the diabetes-prone mice – it neither
increased nor decreased their symptoms, a finding that's been
shown in people as well.

"The only thing sugar has ever been shown to do is cause
dental cavities. It's the fat that appears to be most
detrimental," Feinglos said. Fats are metabolized quite
differently from carbohydrates or pure sugars, he said. A small
candy bar and a bagel may contain the same number of calories,
but they are not necessarily metabolized and stored in the same
way.

"All calories are not equal," Feinglos said. "Carbohydrates
require burning of energy to convert to fat, whereas fat is
directly converted to fat"

The distinction between carbohydrates and fat is an
important one, because it distinguishes the unique role of fat
in contributing to a inherited trait, researchers said. Without
the fat, the diabetes does not occur, even in diabetes-prone
mice. When the high-fat diet is stopped in mice that have been
raised on it, the diabetes disappears.

Surwit said that the animal research provides a basis for
further study of the role of a high-fat diet in adult
Americans, 50 percent of whom are overweight and are, thus, at
risk for developing the disease.

But even in the absence of weight loss in the mice, a
low-fat diet can improve insulin and blood sugar control, the
study showed. That improvement occurred regardless of how long
the mice had previously eaten a high-fat diet, suggesting the
disease process can be manipulated at various points of
progression.

In humans, the disease is less malleable. Irreparable damage
often occurs before it can be reversed, Feinglos said. But if
you identify the disease early and make the appropriate dietary
changes, then the disease could theoretically be modified or
reversed.

"Our findings do point out that, at least in theory, it is
doable," Feinglos said. "Our next step is to find
pharmaceutical compounds to give animals a greater ability to
eat normally, as would the mice without the genetic
predisposition."

While reducing fat intake would be the safest and healthiest
approach to controlling diabetes, experience has shown such
reduction to be difficult to enforce and even harder to
maintain, Feinglos said. Diabetics would theoretically have to
reduce their fat intake to 10 percent of their total caloric
intake, an extraordinarily low percentage, given that most
Americans consume 30 percent of their calories through fat.

But even a more modest decrease in fat intake could have
beneficial effects, the researchers believe. Cutting fat to 20
percent might not reverse the disease, but theoretically could
reduce symptoms and the risk of serious tissue damage.

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