1. Sugary Drinks

Added sugar is the single worst ingredient in the modern diet.  However, some sources of sugar are worse than others, and sugary drinks are the absolute worst.  When people drink sugar calories, the brain doesn’t “register” them as food.  For this reason, people don’t automatically compensate by eating less of other foods and they end up drastically increasing their total calorie intake.
Sugar, when consumed in large amounts, can drive insulin resistance in the body and is strongly linked to non-alcoholic fatty liver disease. It is also associated with various serious diseases, including type 2 diabetes and heart disease.  Sugary drinks are also THE most fattening aspect of the modern diet, and drinking them in large amounts can drive fat gain and obesity.