Today, we know that a high-fat diet, consumed long term, can lead to problems such as obesity, heart disease, diabetes, and a decline in cognitive ability, to name a few. But a recent study by researchers at Oxford University shows it may only take a few days for fat-laden food to begin wreaking havoc on our health.  

To learn more about the short-term effects of a high-fat diet, the researchers conducted an extensive experiment with 32 rats. The rodents were fed a low-fat diet, comprised of 7.5 percent fat, for two months as they trained to complete a challenging maze and to run on a treadmill. The maze consisted of eight different paths with a sweetened condensed milk treat at the end. The goal was for the rats to find the treat without re-entering a corridor where they had already been. Once all the rats had mastered the maze, it was wiped down with alcohol, forcing them to rely on memory rather than their sense of smell.

Then half the rats were switched to a high-fat diet comprised of 55 percent fat, while the remainder was left on their low-fat diet. When retested on the fifth day after the diet switch, the rats eating fatty feed were already running 30 percent less on the treadmill than their counterparts, and by the ninth day were running 50 percent less. The rats on the high-fat diet were also taking longer to complete the maze and making more mistakes during the process. “We expected to see changes, but maybe not so dramatic and not in such a short space of time,” said lead author Andrew Murray, a lecturer in physiology at Cambridge University in Britain. “It was really striking how quickly these effects happened.”

The researchers found increased levels of a protein called uncoupling protein 3 in the muscle cells of the fat-laden rats. This protein makes the cells less efficient at using oxygen to make the energy required for exercising, causing the heart to work harder and increase in size, which may explain their reduced treadmill performance. A possible explanation for the short-term decline in cognitive function is that fatty foods can trigger insulin resistance, which means the body becomes less efficient at using glucose, or blood sugar, which is important to brain function. 

Dr. Gerald Weissmann, editor of the Federation of the American Societies for Experimental Biology, who published the study, described the effect as “nothing short of a high-fat hangover,” noting that “a long weekend spent eating hotdogs, French fries, and pizza in Orlando might be a great treat for our taste buds, but they might send our muscles and brains out to lunch.”

The researchers have also performed similar studies of high-fat diets in healthy young men who then completed exercise and cognitive tests. Dr. Murray said he is still reviewing the data, but the short-term effects of a fatty diet on humans appear to be similar to those found in the rat experiment. “We hope that the findings of our study will help people to think seriously about reducing the fat content of their daily food intake to the immediate benefit of their general health, well-being and alertness,” he said.