Artificial sweeteners are often used in “diet” food products, such as “zero calorie” sodas since artificial sweeteners contain very few calories. However, a Canadian study of 400,000 people over 10 years found that people who used artificial sweeteners tended to gain weight, not lose it. This could be due to various factors.

There is a concern that people who eat more diet foods can trick themselves and replace the calories saved in other ways. For example, people who drink low-fat milk might feel that since it’s low-fat, they can drink more. Or, people might think that because they saved calories by drinking diet soda, then it’s okay to eat a cookie. In this way, they overcompensate and actually eat more calories, leading to weight gain.

Some research suggests that artificial sweeteners can actually change the way our minds perceive the taste of food. Artificial sweeteners are hundreds of times sweeter than actual sugar. Only a tiny amount of artificial sweetener is needed to create an intensely sweet taste. Humans naturally crave sweet foods. Our taste buds change, and we get used to new flavors as our diet changes. Experts from Harvard warn that constant over-stimulation of the sugar receptors can lead to people craving more and more sweet foods, and shunning other foods, that although sweet, are not as intensely sweet as artificial sweeteners, such as fruits. Food that aren’t sweet at all, like vegetables, are then considered disgusting. This can lead to people eating more and more foods with artificial sweeteners, and less foods that are nutritious and wholesome.

As we continue craving foods that are sweet over foods that are nutritious, we gain weight. Researchers found that those in the San Antonio Heart Study who drank more than 21 diet drinks per week were twice as likely to become overweight or obese as people who didn’t drink diet drinks at all.