People call me "skinny" when I have a BMI of 23.7 as of right now. Subjective judgments like that are distorted by comparisons to an overweight, sedentary population.
Back in 2003 I managed to lose over 5 stone, dropping from 17 to 11 and a bit at my lightest although it stabilised at around 12 stone. My first post on the old C+ forum was about that.
Since then about half of that has gone back on. This year I have been between 13-7 and 13-13. Someone at work complimented me the other day on how well I'd done over the long term.
Let's think about that in BMI terms. I'm around 5'11". Max BMI was 33.2, 12 stone is 23.4 and my current 13-8 gives 26.4.
The point being that the last, current, figure is overweight,
but people still think I look thin. I could be nine and a half stone before the formula says I'm underweight. That's how much perceptions have changed. (FWIW I think I would look skeletal if I were under 11 stone.)