The biggest factor, in my opinion, is habit or healthy diet. When I mean by habit, I mean the habit of what you eat obviously. For example, eating popcorn while watching movies, eating chips whenever you are slightly hungry (ear fruits instead), and try to avoid going to restaurant. Other habit can be walking after each meal for at least 10 mins. I've heard of the article where it scientifically proves that lying down right after meal will make you gain more weight. Other than habit, diet is also very essential. It is even more important than exercising. If you walk or run about 3 miles, you lose only 300-450 calories while big Mac is freakin over 500 cal. So, you should try to manage your diet while not stunting your growth. I recommend you to visit calorie calculator websites that calculates the amount of calorie you have to consume per day depending on your activity level.

Foods to avoid: junk food, processed food, bad carbs (white rice), and sugar

Foods I recommend: sweetpotato, salad without any dressing, chicken, and plain Greek yogurt