What is the best way to gain mass??!

What is the best way to gain mass??

I want to gain more mass not fat. I'm almost 14 and I just weigh 90 something, so I am almost underweight. Don't tell me to excercise and gain muscle, becuase I already have great muscles (abs biceps everything) or don't tell me to eat healthy because I never eat any fastfood or any junkfood. So yeah give me some advice.

2 weeks ago
By the way I don't want to use any pills or anything like that.

to gain mass without without fat is not going to happen. you can however minimize the gain in fat by monitoring your portions and your body fat %.

you should be getting 1g of protein to 1lb of body weight.

you should find out your daily calorie requirement and add 500 to it, while keeping your portions in the ratio of 50% carbs, 30% protein and 20% fats.