People started noticing my weight loss after I had lost about 40 pounds and also after I had bought new clothes. As long as I stayed in the old, baggy cothes they did not notice. Each time I go down a size and move from baggy clothes to clothes that fit better, I get a lot of comments telling me that it looks as though I have lost more weight.

My best guess is that you have to lose over 10 percent of your body weight for people to notice. For me, that was about 40 pounds. Since you are smaller, you will lose 10 percent of your body weight faster and people will probably start noticing sooner.