1 - That's factually wrong. It's never too late to improve your diet. The human body is actually remarkably resilient.
2 - One of the most difficult parts of trying to eat healthy is that most people around you are fixed in their ways and will never change. So they will try to drag you back down with them. So that means you're better off keeping it to yourself. Don't tell people what you're doing. Not only that, but having a very active social life conflicts with health goals because people are mostly eating unhealthy. You may need to radically change your social life to stick to serious health goals. Are you ready to do that? If not, you might not make it.