The most I ever lost in recent years was when I went on Kaiser's medically monitored weight-loss program (a soft prerequisite to be eligible for bariatric surgery through them). Liquid diet, 860 calories a day, frequent blood work, etc. I lost 50 lbs in 3 months. Gained it all back over the following year. Fearing all the side effects, I never ended up doing the bariatric surgery.
This time around I'm not "cheating" my way through it. Keeping track of everything religiously has kept me honest about what I'm eating, and I've been taking a 3+ mile walk most days. Been trying to keep a pace that makes me sweaty even in the cool weather of my area. I'm back down to the weight I was after the Kaiser thing (50 lbs lost), but I'm not craving all the things I did then.
Diet has basically been whole grains, lots of veggies, turkey, fruit, nuts, oats, and the occasional fish. Overnight oats is my go-to breakfast - steel cut oats, chia seeds, soy milk, fruit, nuts. I've been making a bunch of things from the Forks over Knives vegan diet. I can't bring myself to go full vegan, I love fish too much. Either way, mostly keeping it under 1700 calories a day.
I recently joined my friends' gym group and plan to go regularly. Been keeping up with them for the last two weeks so we'll see where that goes. Maybe try to get some muscles to fill in some of the loose skin I'll have.