Based on this suspicion, her team attempted to isolate the effects of fat on the animals' brains. Researchers did this by exposing the animals to fat in different ways: by injecting various types of fat directly into the brain, infusing fat through the carotid artery or feeding the animals through a stomach tube three times a day. The animals received the same amount of calories and fat; only the type of fat differed. The types included palmitic acid, monounsaturated fatty acid and oleic acid.
Palmitic acid is a common saturated fatty acid occurring in foods such as butter, cheese, milk and beef. Oleic acid, on the other hand, is one of the most common unsaturated fatty acids. Olive and grapeseed oils are rich in oleic acid.
"We found that the palmitic acid specifically reduced the ability of leptin and insulin to activate their intracellular signaling cascades," Dr. Clegg said. "The oleic fat did not do this. The action was very specific to palmitic acid, which is very high in foods that are rich in saturated-fat."
Dr. Clegg said that even though the findings are in animals, they reinforce the common dietary recommendation that individuals limit their saturated fat intake. "It causes you to eat more," she said.
The other key finding, she said, is that this mechanism is triggered in the brain long before there might be signs of obesity anywhere else in the body.
The next step, Dr. Clegg said, is to determine how long it takes to reverse completely the effects of short-term exposure to high-fat food.
|Contact: Kristen Holland Shear|
UT Southwestern Medical Center