well from my own experience there's a percentage of body fat where you actually start some sort of starvation mode where you have 0 energy whatsover. during the evening i used to stare at the wall for like 4 hours before going to sleep because i had no interest in anything. it was quite peaceful though.

Also I felt that some muscle parts were deteriorating so I had to stop.. i would not recommend anyway but it was a fun experience.

I also realized something: body image perception is subjective.. i did that because I thought I was fat. when I took 1kg more after that and I was at 69kg i though it was the end of the world. now i'm like 10 kg more and even though i still think I'm fat, I don't think I'm 10x more fat than back and actually I think I look slightly better (there are other factors.. i do thai boxing so I have more muscle shape also..).

The point is I always felt the same at every weight. I felt "I'm fat". Now I just learnt to live with the "i'm fat" thought into my head and i'm good lol.