This diet would mean eliminating fats and calories; just enough should remain for fueling muscle growth. In the latter, it is the opposite, a skinny kid should eat more but should have the proper intake so that body fat is not created, rigorous strength training should be done simultaneously to build up bulk, mostly of muscles.
It is not advisable to immediately push a teenage boy into a full intense workout as their body is still developing. They should be gradually introduced in the program to allow their body to adjust. Make sure also that they have sufficient rest as teenage boys are a bundle of energy. Redirecting this energy in a well planned workout program will allow them to maximize the use of their energy.
Most importantly though it is the attitude that should be set first before embarking on a gaining muscle journey. Teenage boys are easily distracted and they can easily forget that they are working on a goal. They must be determined to finish what they will be starting. With full commitment, they will be able to achieve success in gaining muscle in no time at all.
These are just some of the things one must consider when starting a program of gaining muscle. There are lots more, but most importantly, it is all about discipline. Having a healthy and great looking body works wonders to a person, especially to a teenage boy. There is nothing quite like the present to start on this fruitful journey. So there you go.