Why a High-­Fat Diet Can Torpedo Your Metabolism

High-fat diets may be trendy| but you might want to rethink all-cheese-all-the-time: a high-fat diet resets your metabolism| making it harder for your body to burn calories| reports a new study in Obesity. Even more shocking is the fact that it takes less than a week to undo all the hard work from your high-intensity interval classes.

“Most people think they can indulge in high-fat foods and get away with it| but all it takes is five days for your body’s muscles to start to protest|” said Matt Hulver| an associate professor at Virginia Tech and lead author| in a press release.

In the study| healthy students traded one meal a day for similar calories consisting of 55 percent fat ü?mainly the unhealthy saturated kinds. The results: eating that much fat for a workweek reduced people’s muscles ability to oxidize sugar postdining. Why that matters: muscles are the primary way your body process sugar. If they can’t do their job ü?in this case because fat is interfering ü?you can wind up with insulin resistance| which can lead to diabetes| high blood pressure| and of course| weight gain.

These findings are backed up by research published last year in Biological Psychiatry| which found that people’s metabolisms slowed after just one high-fat meal. (Learn The 7 Biggest Myths About Metabolism ü?Busted.) To make sure this effect wasn’t just from the unhealthy saturated fats people were given| Janice Kiecolt-Glaser| PhD and lead author of that study| repeated the experiment using healthy fats like the polyunsaturated oils found in canola and olive oil. Surprisingly| the results were the same ü?regardless of the type of fat!

Over time| Kiecolt-Glaser estimates that indulging oing once a week in a high-fat meal could add up to an 11-pound weight gain in one year. And that’s just from one meal. Hulver points out that| if you’re consistently eating a high-fat diet| the effect could be much larger. Even more: any time your metabolism is altered| it can have dire consequences| not just for your weight but also your whole body. But before you freak out| counting the number of weekends you’ve succumbed to pizza binges| Hulver’s team cautions that more studies need to be done| especially to look at the different unhealthy ingredients in foods. (In the meantime| snack on 15 Smart| Healthy Alternatives to Junk Food.)

And also remember that the effect can be reversed. We all have a powerful tool for increasing metabolism| says Keicolt-Glaser: exercise.

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