This is a hypothesis and it is being challenged by many… But in a nutshell here it is: when we eat bad sugars, they unnaturally quickly are absorbed into the bloodstream. In attempt to clear them from the bloodstream, the body produces insulin. Insulin is a growth hormone and a hormone that among other things stimulates the deposit of fat. Insulin lowers the serum glucose rather quickly, and very often may overdo and make it even lower than our body likes, which in response makes us hungry and craving for more sugars, we have another bite, and the cycles repeat again. So, it appears that consuming bad sugars converts our body in fat production machine that pumps sugars from our guts into the fat tissues while leaving our resultant serum glucose low and our body craving for more sweet treats.