Fatties are also terrible at noticing the nuances of how fit people eat. Using the OP's Subway example, the "thin friend who eats twice as much" might order a footlong sub which is topped with lean chicken and lots of veggies, while the fatty orders a 6-inch sub which is stacked to the ceiling with fatty meats, cheeses, and oozing super caloric sauces, etc. The thin friend's sub actually ends up containing far fewer calories, but the fatty only sees "his sandwich is twice as big, so he must be able to eat whatever he wants and never get fat!"