There was a stretch in the 90's when I did lose some weight and stabilize at a certain size, with 1.5 hours of gym time DAILY and under 25 grams of fat most of the time. (Those times I "screwed up" and ate lots of fat might have been good for me.)

However, I was in bed recovering from an operation and the whole thing collapsed. Without constant activity to burn up the carbs, I just gained weight.

But with age and increased stress and inability to keep up with that kind of effort due to life changes it never worked again.