New research suggests sugary high-fat foods may impair the brain’s ability to make good decisions about diet and even fuel overeating in obese people.
The study, by Terry Davidson, director of American University's Center for Behavioral Neuroscience, indicates that diets high in saturated fat and refined sugar cause changes to the brains of obese people that make weight loss more difficult.
"It is a vicious cycle that may explain why obesity is so difficult to overcome," said Davidson.
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The findings, published in the journal Physiology & Behavior, are based on experiments involving laboratory rats given high-fat, high-calorie food that made them obese. Compared to rats fed low-calorie diets, those consuming unhealthy foods performed much more poorly on tests of learning and memory.
The results suggest such diets may change the brain’s ability to make good choices about food, the researchers said. Davidson said the research identified changes in the region of the brain known as the hippocampus, which is involved in memory and decision making. Researchers said it could be that a diet high in saturated fat and refined sugar impacts the hippocampus's ability to suppress unwanted thoughts – such as those about high-calorie foods – making it more likely that an obese person will consume those foods and not be able to stop at a reasonable serving.
"What I think is happening is a vicious cycle of obesity and cognitive decline," Davidson said. "The idea is, you eat the high fat/high calorie diet and it causes you to overeat because this inhibitory system is progressively getting fouled up. And unfortunately, this inhibitory system is also for remembering things and suppressing other kinds of thought interference."
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Davidson's findings echo other studies linking human obesity in middle age and an increased likelihood of developing Alzheimer's disease and other cognitive dementias later in life.