I don't think a 100 pound person needs to lose weight as it is already skinny.
It is quite possible for someone
not to be 'skinny' at 100 pounds (7 st 2 lbs) -
IF THEY ARE SHORT ENOUGH!
I admit that very few people
are that short but my sister just told me that she has a friend who is 4' 11" tall, weighs about 93 pounds (6 st 9 lbs) and is slim, rather than skinny. If she put 7 pounds on she might very well want to lose it again.
I have a friend who is 5' 1" who weighs 100 pounds and she thinks that is about the perfect weight for her. She lost weight through illness a couple of years ago and looked terribly skinny then.
My original point was actually that small people should only lose weight slowly -
IF AT ALL!