It's not something new you need to know that's holding you back. It's finding out what is holding you back. You most likely know what things you should eat. You most likely know that exercise is good for you. Lift some weights, do some cardio. Get stronger, improve your endurance.
You know broccoli is good for you and that beer and cake is not.
What you need to focus on instead is this question:
What is holding me back? What beliefs or thoughts are handcuffing me?
You have to get your foot off the brake before you can move forward.
And this brake is your beliefs and mindset. And here's where you can start: do you have a fixed mindset or dynamic mindset?
Just knowing that these two exist will begin to move you to the dynamic mindset.
Now go and eat some broccoli.