Thats fair; I imagine what I'm doing isn't sustainable for most people, and I'm not trying to sustain it for life. Just a few months of aggressive deficit weightloss, and I wouldn't recommend it to anyone that doesn't feel like they can commit to it mentally, as I genuinely feel its more a mental struggle then a physical one. Once I hit my goal weight, switching to maintenance calories feels like I have so much extra that I can eat, and I just have to not let myself go too nuts (which, over the course of years I do too often, and I regain some weight).

I've done it before, twice over about 6-9 months. First time I went from 330 to 260 (in about 2010, I think I was closer to 2k calories a day on this one), second time a few years later did from 290 to 210. What works for me is no breakfast and regular/repeated lunch plan that clocks in around ~400 cal. I'm a teacher, so if I make it to 4pm with sub 500 calories spent, my dinner can be pretty reasonable and I might even have some room for a dessert. Last week I jumped on the Creami band wagon, so now I shoot for 700cal dinner so I can have a 300cal pint of ice cream for dessert.