Most of us know that junk food is unhealthy. We know that poor nutrition is related to heart problems, high blood pressure and a host of other health ailments. You might even know that studies show that eating junk food has been linked to increases in depression.But if it’s so bad for us, why do we keep doing it? There is an answer. The science behind it will surprise you.When you eat tasty food, there are two factors that make the experience pleasurable. First, there is the sensation of eating the food. This includes what it tastes like (salty, sweet, umami, etc.), what it smells like, and how it feels in your mouth. This last quality known as “orosensation” can be particularly important. Food companies will spend millions of dollars to discover the most satisfying level of crunch in a potato chip. Their scientists will test for the perfect amount of fizzle in a soda. These factors all combine to create the sensation that your brain associates with a particular food or drink. The second factor is the actual macronutrient makeup of the food. The blend of proteins, fats, and carbohydrates that it contains. In the case of junk food, food manufacturers are looking for a perfect combination of salt, sugar, and fat that excites your brain and gets you coming back for more.The good news is that research shows that the less junk food you eat, the less you crave it. Some people refer to this transition period as “gene reprogramming.” Whatever you want to call it, the lesson is the same: if you can find ways to gradually eat healthier, you’ll start to experience the cravings of junk food less and less.