How a High-Fat Diet Could Slow Down Your Metabolism

Before you head to the buffet line and pile mac-n-cheese and hot dogs on your plate for the third night in a row, take a moment to read this. A new study in the journal Obesity found it took only five days for your body to feel the effects of a high-fat diet, and potentially impact your metabolism.

Researchers placed 12 healthy, young men on a 30% fat diet (the Institute of Medicine recommends fat should comprise anywhere between 20 and 35% of your diet). After a week, they moved the participants to a high-fat diet. Half of the individuals received 55% of calories from fat, while the other group received 63% of their calories from fat.

To test the results of this sudden change, scientists took muscle biopsies before and after the experiment. After five days of eating macaroni and cheese, ham and cheese sandwiches with butter, and frozen dinners, the subjects’ metabolisms took a turn for the worse. “The normal response to a meal was essentially either blunted or just not there after five days of high-fat feeding,” said study author Matthew W. Hulver, PhD, Department Head of Human Nutrition, Food, and Exercise at Virginia Tech.

Normally when you eat, your body converts the carbs you consume to glucose (blood sugar), which is then delivered to cells via a hormone called insulin. In the cells, the glucose is converted into energy. When you consume too much sugar, your cells can start to reject insulin. This is called insulin insensitivity or insulin resistance. It causes an excess of blood sugar and often leads to type 2 diabetes.

Dr. Hulver analyzed biopsied muscle from the test subjects and discovered the muscle no longer used glucose as an energy source. While the Time article points out that the five-day binge wasn’t enough to impact overall insulin sensitivity, this reaction in the muscle indicates it could over time.