5 Days of a High-Fat Diet: the Impact on Your Body

What 5 Days of a High-Fat Diet Does to Your Muscles
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Can’t resist that donut at breakfast, followed by French fries for lunch? Not so fast. New research reveals that overindulging — even for just a few days — might have more of an impact on your body than you’d expect. According to a recent study from Virginia Polytechnic Institute, eating a high-fat diet for just five days can change the way your muscles metabolize nutrients, leading to a higher risk of heart disease or diabetes.

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Previous studies in rodents have demonstrated that a high-fat diet can rapidly alter how muscles digest the macronutrients, such as protein, fat and carbohydrates, that provide your body with energy. Dr. Matt Hulver, an associate professor at Virginia Tech, designed a study to examine the effects of a high-fat diet in humans.

What male college student wouldn’t volunteer to eat a high-fat diet in the name of science? Researchers observed 12 non-obese, college-aged male participants as they consumed fat-laden diets that matched their usual caloric intake. The men consumed 55 percent of their calories from fat, 30 percent from carbohydrates and 15 percent from protein. A whopping 25 percent of those calories came from saturated fats. (Recommendations from the Centers for Disease Control and Prevention suggest limiting overall fat consumption to 20 to 35 percent of your daily calories.)

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“This study wasn’t just a blanket high-fat diet,” says Dr. Hulver “It was purposefully designed to look at high saturated fat.” He says that participants were fed heavily processed, pre-packaged convenience foods, some of which were microwave meals and snacks. Each day, researchers conducted muscle biopsies and recorded bodyweight and fat percentages for the participants.

Big Fat Surprise

While these college guys didn’t develop beer guts overnight (they, in fact, experienced no weight gain), their bodies did undergo some hidden changes. Researchers found that participants’ high-fat diets disturbed their ability to oxidize glucose in their muscles after just five days. Why does this matter? Glucose, which comes from carbohydrates, is responsible for providing your cells with energy and controlling blood sugar levels. When you eat a meal, your glucose levels rise and then fall as your body works to either convert these carbohydrates to energy or store them for later use, in the form of fat.

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Hulver explains that, though more research is needed, consuming high-fat foods may increase the possibility that glucose is stored in the body as fat. Additionally, previous studies have demonstrated that a disruption in metabolism and high blood glucose levels can be a risk factor for health issues like diabetes.

“I didn’t expect to see such a robust effect on how the muscle responds to a meal in such a short amount of time,” says Dr. Hulver. He notes follow-up studies are already underway to determine exactly why a high-fat diet can so quickly influence how the body metabolizes glucose.

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So how dangerous are burgers, bacon and other fatty foods? Even if you’re keeping your total calorie count under control, a fat-heavy diet won’t do your health many favors.

“Independent of increased calories, if you have a chronic consumption of saturated fat, it changes the way your body responds to a meal,” says Dr. Hulver. Watching your portion sizes is crucial for maintaining a high-functioning metabolism. In other words: If you have a soft spot for fatty meats and cheeses, it might be worth tracking macros to ensure a balanced, healthful diet that’s got less than 30 percent of calories from fat. Wield that butter knife responsibly!

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