Science has proven that eating a sensible amount of “good” (mono- and polyunsaturated) fats, like those in avocados, nuts, and fish, can lower your risk of heart disease and stroke, while saturated fats—the kind doughnuts and chips are dripping with—can raise cholesterol and increase your risk of heart disease. But, a warning: Just five days of fat-bingeing—eating 55% of your daily calories in fat—can muck up your metabolism and open the door to disease, according to a new Virginia Tech study.
In it, healthy college-age guys ate a typical diet of 55% carbs, 15% protein, and 30% fat (11% of which was saturated fat) for a week, to normalize their diet and set a baseline; they then loaded up on super-high-fat foods, to flip the ratio to 30% carbs and 55% fat (including 25% sat-fat).
The results were swift and shocking: The fat glut sabotaged the way subjects’ muscles metabolized nutrients and oxidized glucose. This stalled the body’s insulin response—a step toward obesity, diabetes, and other diseases, and multiplied endotoxins, bacterial waste that wreaks inflammatory havoc.
Even the researchers were surprised. “This was the first study in healthy males to show that a short-term, high-fat diet can raise endotoxins in the blood—early cues to obesity and diabetes,” says Matthew Hulver, Ph.D.
Lesson: Enjoy good fats in moderation, and have the odd cheat meal, but submit to the lard too often and it’s medical salvation you may end up needing.