WHY WE THINK IT’S HEALTHY:

It has no calories and allows dieters to enjoy their soft drinks guilt-free. The classic way to lose weight has been to eat fewer calories than you burn, so drinking low-calorie pop should, in theory, help you shed those unwanted pounds more easily.

WHY IT’S NOT:

The principle of “a calorie is a calorie” is based on the second Law of Thermodynamics, and has been the prevailing theory on why we gain or lose weight. If we eat too many calories, we gain; if we eat too little, we thin out. If this were true, then 100 calories of candy should be the same as 100 calories of broccoli. Intuitively, we know that that’s not true, and research proves that it isn’t. Although calories still count, our hormonally complex metabolism gets in the way of the Law.

When it comes to diet sodas (and anything else that contains artificial sweeteners), we actually find that the opposite is true: They actually make us fat. Population studies show that there was a 200% increased risk of obesity in diet soda drinkers. In fact, diet sodas are worse than the full-on sugary types. A study published in the American Journal of Clinical Nutrition showed that diet sodas raise the risk of diabetes more than sugar-sweetened sodas. They’ve also been associated with metabolic syndrome, depression and preterm delivery. Although these observational studies can’t prove that diet drinks cause anything, they nonetheless show a strong correlation with conditions that we were trying to avoid by drinking the stuff in the first place.

Scientists think that this happens because artificial sweeteners fool our brains into thinking we just ate sugar, causing our pancreas to pump out insulin. Insulin stimulates fat storage and lays down more belly fat. Artificial sweeteners also stimulate your hunger and make you crave more sweets and starchy carbs like bread and pasta. There’s no free ride when it comes to soda — it needs to be kicked out of your diet.