“fat cells burn around 2.05 Calories per pound, so you’d gain a lot of weight” in order for for the extra fan to burn off the extra calories you’re eating.
when you eat, there are always bits of food that either can’t be digested by the human digestive tract (fiber, or really complex carbs, for instance) or doesn’t get digested due to time/space constraints (you ate too much too fast). Your gut is home to an extraordinary number of microbes, and these lovely bacteria feed on your “leftovers”, producing gas. Those noxious smells, if you’re wondering, are sulfur compounds. :-)