" I wonder if killing the sense of smell is essential, in order to conceal the smell of dead people dropping like flies if their plan worked like they hoped.. " More likely it's to get the supermajority of people to eat less. Eating releases endorphins and dopamine as part of it's sympathetic nervous system for survival. Plus, when all food tastes like nothing, you'll be more susceptible to choking down bowls snot https://www.youtube.com/watch?v=zuUtAPUZP0Q Or bugs / plants.