Yes, 100%.
As a teenager I didn't really care much about myself. I was fat, unsociable, had bad skin, completely lacked in confidence, and had the worst sense of fashion ever. I did have some amazing friends, who I am grateful for of course, but my teenage years were nothing like those that I saw other people having. I was never (and have still never been) one of the "popular" people.
I have now lost weight, and sorted my skin and fashion sense, and my confidence is growing. I feel like I have made up for my teenage years somewhat, but it just isn't the same or anywhere near as care free now I'm well into my twenties.
Trust me, anyone reading this who feels this way, try your best to change things, or you will regret it.