November 17, 2008

Obesity Thought To Be Preprogrammed At Birth

New research from Rockefeller University suggests that pregnant women who consume high-fat diets may cause changes in their developing fetus' brain that could lead to obesity early in the child's life.

The scientists conducted their research on rats, and found that those born to mothers fed on a high-fat diet had many more brain cells specialized to produce appetite-stimulating proteins.

The researchers say their study may help explain the surging rates of obesity in recent years.   

Prior studies on adult animals have shown that fats known as triglycerides stimulate the production orexigenic peptides, proteins in the brain that stimulate the appetite.

Not surprisingly, the current study suggests exposure to triglycerides from the mother's diet has the same effect on the developing fetal brain.  Furthermore, the effect appears to last throughout the life of the offspring. 

The Rockefeller University scientists compared the offspring of rats fed a high-fat diet for two weeks with those whose mothers consumed only a moderate amount of fat.

They found that the offspring of the mothers fed a high-fat diet ate more and weighed more throughout their lives, and began puberty earlier, than those born to mothers fed a normal diet.

Additionally, they had higher levels of triglycerides circulating in their blood at birth, and as adults, and a greater production of orexigenic peptides in their brains.

A more thorough examination revealed that even before the birth, the high-fat pups had a substantially larger number of brain cells that produced orexigenic peptides, which the offspring kept throughout their lives.

It appeared that the mothers' high-fat diet stimulated production of these cells, and their later migration to parts of the brain linked to obesity.

However, rats whose mothers ate a balanced diet were found to have far fewer of these specialized cells, and they appeared much later after birth.

"We believe the high levels of triglycerides that the fetuses are exposed to during pregnancy cause the growth of the neurons earlier and much more than is normal," Lead researcher Dr Sarah Leibowitz told BBC News.

"This work provides the first evidence for a fetal program that links high levels of fats circulating in the mother's blood during pregnancy to the overeating and increased weight gain of offspring after weaning."

The researchers hypothesized that the fetal brain may be programmed so that the offspring can survive on the same diet as their mother, a mechanism they believe also exists in humans.

"We are programming our children to be fat," said Dr Leibowitz.

Dr Ian Campbell, medical director of the charity Weight Concern, said that although it was previously known that a high-fat diet during pregnancy made a child more prone to prefer fatty foods, it was not yet clear why this was so.

"The message is clear. We are not just 'what we eat'; we are also to some extent 'what our mothers eat," he told BBC News.

"The time to start feeding your child a healthy diet is right at the beginning of pregnancy."

According to obesity expert Professor Ian MacDonald at the University of Nottingham, there is clear evidence that nutrition before and soon after birth has a continuing genetic impact.  However, he cautioned against

But he warned against reading too much into studies on animals, particularly since the rats in the current study were fed a very unusual diet.

The study was published in the Journal of Neuroscience


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