But not foolish.
It's great wanting to lose 100 pounds in 1 year...
But trying for 2 pounds a week for 25 weeks is hard when you struggle to lose 1 pound a week.
And what do you do when you start hitting your plateaus? Progress isn't linear.
Do you eat less?
If you're already are your minimum viable calorie consumption, you're starving yourself.
Fasting is great, but it's not a long term solution. Starving yourself is a great way to retain water, compromise liver and kidney function, and throw your hormones out of whack.
Consider the alternative.
If you have been gaining weight, first learn to stabilize your weight.
Try a weight stabilization diet for a few weeks and find out what's sustainable for you which also achieves the goals your are looking for.
Once you learn how to maintain your weight, practice losing 1 pound a week.
That about a 500 calorie deficit a day. A combination of dietary habits and increased exercise will get you there easy.