The only real piece of advice I have for changing those things is committing to it. Losing weight is a good place to start, it has easily observable results and you can go at your own pace. I lost 20kg in 6mo when I started travelling, it was my first "change my life" goal and it made it a lot easier to start on other things that I hoped would be beneficial for me long-term - like finally starting on getting my teeth fixed despite my fear of dentists.

Finding the first win helps a ton. :)