I picked my listed goal weight for similar reasons to you in that it was 100lbs less than my highest weight. I was also 140lbs in high school and was very athletic then. However, my eating habits were WAY off (I don't think I ate a lot of calories but I ate very unhealthy foods) so I think between working out in a more efficient manner now-a-days and eating well it would be something I could easily maintain. HOWEVER; my main goal is to get to 155lbs now. I'm weight lifting (didn't in high school) and have been doing so for about half a year now so I can imagine by the time I get to a healthy BMI I might be content earlier on than 140lbs.
I also want to be in at least a size 8 or smaller and have a 28" waist or smaller so if that comes before 140lbs, I might just stop there.





