Don't make the same mistake of oversimplifying diet that led to the "fat is bad" and "fat makes you fat" myths.

Neither fat nor carbs are "bad" for you. Eating too much saturated fats plus a sedentary lifestyle is bad for your heart, pretty much independent of your weight. Eating too many refined carbs (foods with a high glycemic index) is also bad for you and can facilitate weight gain and potentially lead to other health problems in people who are genetically predisposed (e.g. type 2 diabetes). However, eating a Mediterranean diet high in unsaturated fat and whole grains (fat and carbs) is one of the healthiest diets possible according to a huge volume of research, so just throwing around the "fat" and "carbs" labels is not necessarily helpful.