Fake sugars cause weight gain.

When we taste something sweet, our bodies prepare to burn calories. But what happens when no calories arrive? This study from Purdue University—the first to test this question—looked at how rats responded to zero-calorie artificial sugar (saccharin).

For two weeks, one group ate saccharin-sweetened yogurt while another ate sugar-sweetened yogurt. Even though the sugary yogurt had more calories, the rats eating zero-calorie saccharin ate more food and gained more weight than the rats consuming sugar—eek!

Your body has a natural response to food that regulates your metabolism. Sweet tastes predict calories, so your body knows to rev up in order to burn them. When those calories don’t come (like with fake sugars), that relationship breaks down. You burn fewer calories and gain more weight.

Worse, fake sugars may actually retrain your body so that you eat more calories and burn fewer no matter what you eat. We may be clever, but we can’t outsmart Mother Nature! 

In the past 20 years, fake sugar consumption has more than doubled, and so has obesity. Enticing commercials feature slim women showing off refrigerators full of artificially sweetened yogurt, or drinking zero-calorie sodas. We’ll admit—we’ve tried our share of these yummy treats. But if you want to keep your waistline whittled, go for real sugar. Better yet, choose fruit instead and let natural sugars satisfy your sweet tooth.