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Saturated fat tells our brain to keep eating

Kathleen Blanchard's picture

New research shows that eating saturated fat in foods, especially one particular type of fat, tells our brain to keep eating. The findings explain why splurging on ice cream and burgers can sabotage our efforts to control appetite and lose weight. The study also contributes to understanding how insulin resistance develops.

Research from UT Southwestern Medical Center, led by Dr. Deborah Clegg, shows that palmitic acid, found in beef, butter, cheese and milk, and is an instigator that tells the brain we need to keep eating. Additionally, the effects can last up to three days, explaining why eating high fat foods on the weekends seems to make us hungrier come Monday. The fat molecules signal the body to ignore hormonal signals from leptin and insulin that suppress appetite.

According to Dr. Deborah Clegg, assistant professor of internal medicine at UT Southwestern and senior author of the study performed on rodents, "What we've shown in this study is that someone's entire brain chemistry can change in a very short period of time. Our findings suggest that when you eat something high in fat, your brain gets 'hit' with the fatty acids, and you become resistant to insulin and leptin. Since you're not being told by the brain to stop eating, you overeat."

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The researchers fed rats different types of fat with the same amount of calories for the study - palmitic acid, monounsaturated fatty acid and oleic acid. They injected various types of fat directly into the brain, through the carotid artery or fed the animals through a stomach tube three times a day.

"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."

Though the study was done on animals, Dr. Clegg says the findings reinforce the fact that we need to limit saturated fat in the diet. "It causes you to eat more," she says. Before obesity develops, foods that contain saturated fats signal the brain to keep eating. The next step is studying how long it takes to completely reverse the stimulating effects on appetite of eating a high fat diet.