Diet soda has long been advertised as the healthier alternative to regular old fat soda. But as I learned previously while analyzing all the ingredients in Diet Coke, the artificial sweeteners in diet sodas (specifically aspartame) will still fuck you up pretty bad: “Even though Diet Coke might not have the calories that a regular Coke does, artificial sweeteners still affect our hormones like insulin in ways that can make us hungrier and reduce the amount of fat we burn,” physician and biochemist Cate Shanahan, author of Deep Nutrition: Why Your Genes Need Traditional Food, told me at the time. As a result of the above, diet soda might even cause you to gain more weight than regular soda.
One 2016 study showed that low-calorie sweetener users tend to have a higher average body mass index, a 2.6-centimeter larger waistline and a 53 percent higher incidence of abdominal obesity compared to participants who reported never using low-calorie sweeteners. Similarly, a 2008 study found that drinking artificially sweetened beverages was associated with an almost doubled risk of being overweight or obese.
For this reason, diet soda manufactures were sued last year for deceiving consumers into believing their beverages would help them lose or manage weight, when in reality, scientific studies have shown that they do the exact opposite. [Source]