Tummy Tuck Worth It on Loose Skin for a 17-year-old?

You have lost weight around the abdomen area.  The skin changes show this very well.  You are male and a young man with a great looking upper abdomen.  I would just excise the extra skin to make the area nice and tight.  also putting the incision as low as possible.

Although you did not specify this, you look like you lost a fair amount of weight and have been exercising and have good muscle tone. The stretched out skin of the lower belly really compromises what you have achieved. That skin is not going to improve as you get older. You do not need a full tummy tuck procedure as you don't appear to have muscle separation. What you do need is a skin-only tummy tuck. This would be done through a long, horizontal incision just above your pubic area. The scar would be low enough to be hidden under the waist of low rider jeans.
It is not common that I would recommend a surgery like this in a 17 year old, but I would guess that you are self conscious about the way your belly looks. At your age it would be great to feel good about wearing a swim suit.