Just eat balanced (omnivore, vegan, vegetarian, all can be balanced and all can be full of junk food) and if you have a smart watch, look at the calories you burnt in the day. Try not to eat more than what you burn.

Be sure to have at least something like 30 minutes 2 days out of 3 where you do sport (workout, whatever you like) and really sweat. Your smart watch can help you doing it with gamification/challenges/you name it.

It is simple, very simple, the hard part is to just do it and keep doing it.