72 hours of not feeding myself was a dreary commonplace when I was a teenager. I absolutely can go days at a time without eating. It got me down to 137 from 237 in the space of four months. It also makes me light-headed and despondent.
I've pretty much gotten used to being dizzy and despairing by 4pm. Eating enough to not be that way means I gain a pound a day. When I was riding to work I had to time dinner such that I actually had enough available calories to make it home without seeing stars.
And still I lost no weight.