I eat about 4000 calories a day and I am very lean. When I was eating
high carb, I would gain weight if I went over 2500 calories. Without
insulin present, it is darn near impossible to add fat to your body. If
you eat too much though, you will have a harder time losing (even on 0
carb) but you won't gain any fat either.

I would keep the calories up but start exercising too. If you don't like
to exercise, then you must reduce the calories but stay as close to 0
carbs as you can.