This isn’t the first time diet products have been suspected of causing weight gain; some studies show that diet soda might show a similar pattern.
Study author Susan Swithers told the LA Times that sweet tastes prompt the body’s digestive system to get ready to process caloric food. But when the calories don’t arrive because the sweetness was artificial, the body learns not to crank up the metabolic furnace. Over time that adjustment makes it it harder to burn calories and shed weight.