About the smell/appetite thing: When you smell, you are ingesting very small caloric amounts of that food (like maybe 1 calorie). I hope we're not ingesting the stank of fats when they're nearby . . .  You know how lots of restaurants will have that smell outside? Like bakeries or fast food places? They're trying to stimulate a hunger response. If you smell something baking you ingest that 1 calorie, and your body thinks you're getting food soon, so your stomach starts to rumble and you think you're hungry, so you buy their food. That's the idea, at least.