Why Ice Cream Tells Brain to Keep Eating

Fat molecules from some foods can change brain chemistry in a short time, causing appetite-suppressing signals to be ignored, U.S. researchers say.

Dr. Deborah Clegg, assistant professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas, and colleagues attempted to isolate the effects of fat on animals' brains by exposing them 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.

Palmitic acid is a common saturated fatty acid in foods such as butter, cheese, milk and beef. Olive and grape seed 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," Clegg, the senior author, said in a statement. "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."

The study's findings, published in The Journal of Clinical Investigation, suggest that when people eat something high in fat, the brain gets 'hit' with the fatty acids and become resistant to insulin and leptin -- which tell the brain to stop eating and people overeat.