I don’t know if this worked, or just good genes (my mom & aunt have fab skin in their 60s), but I’m a diligent dry brusher and I think it’s helped. I lost a little over 60lbs in 6 months and have no loose skin other than a little on my inner thighs (and if I’m being honest, it’s probably more noticeable to me than anyone else), but even that’s started to tighten up. I do it daily before I shower (takes like 2 minutes), then coconut oil after while still damp. Bonus my skin is crazy soft!
Things people say help: longer fasts (72 hours) on a regular basis, dry fasting (not recommending esp w/o research), collagen, dry brushing (Google). Skin will continue to shrink for a year or 2 after your weight stabilizes. Good luck! Fung has said they have never referred anyone for skin surgery but people working with The Fasting Method do tend to do longer fasts regularly, a lot of people on this sub do time restricted eating instead. You might also want to check out r/fasting. Good luck!