A good reason not to cheat on your diet

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It can be fun to indulge in the occasional break from healthy eating, maybe with ice cream and cheeseburgers during summer vacation, or cookies and pie at the holiday season.

But even a brief switch to a high-fat diet may alter how our bodies process food, according to a preliminary study published this month in the journal Obesity. Researchers found that high-fat foods can affect one’s metabolism in as quickly as five days.

In a small experiment at Virginia Tech, 12 healthy college males ate a diet high in saturated fats — 25 percent as compared to 11 percent in a normal diet — for five days, consisting primarily of prepackaged, microwavable foods, such as macaroni and cheese and sausage biscuits. Notably, the volunteers did not consume any more calories than they typically ate prior to the experiment.


Before and after the five-day diet change, nutrition professor Matthew Hulver and colleagues fed the volunteers a high-fat meal then took small samples of skeletal muscle tissue from each volunteer’s upper thigh. Muscle tissue is critical for breaking down or storing glucose from food that we eat.

Hulver’s team tested the muscle samples to determine the rate at which the tissue was metabolizing, or breaking down, glucose from the meal. They found that the muscle cells metabolized glucose at a slower rate after the five days of high-fat eating than they had before. The post-high-fat diet cells also had increased numbers of inflammatory molecules and altered levels of metabolic proteins, indicating widespread changes in the muscle tissue.

“Just by increasing the amount of fat, and specifically saturated fat, we are able to show the response to a meal in skeletal muscle seems to be altered,” says Hulver. “Now is that a bad thing? We don’t know.”

Earlier research had yielded similar findings, but the effects of a high-fat diet in the muscle of non-obese individuals had not been studied. In fact, Hulver had found that a high-fat diet altered the metabolism of muscle tissue in rodents.


To determine the health implications of the finding Hulver is planning additional studies looking at how the observed short-term changes affect the body over a long period of time, and if those changes can be reversed by returning to a low-fat diet. If not, the metabolic changes could make an individual more prone to weight gain, Hulver speculates, though none of the volunteers in the present study gained weight over the five days.

Future studies will also extend the work to women and individuals of different ages. “This is a proof-of-concept study,” says Hulver. “We can’t say all human beings will react in the same way.”