It's because their meals would either be considered treats for us or straight disgusting. Fats seem to only eat high calorie foods and things like veggies or fruits are only eaten for show or are mutilated with butters, sugars, creams, etc. They also drink way more calories than a normal human. Multiple Starbucks extra tall, super whip cream dreams a day will begin to show. They also fry almost everything if they can. They seem to try to find the most over the top ways to pack in as many calories as possible per meal.