I want to take serious mass gainer supplement. i am 22. thin and want to build my muscle, i just started gym.my gym trainer suggested.

Do not take it: Being thin is not a disease. Do not worry about it. As you age you will gain weight and look back at this time fondly when you could eat and not get fat. The proposed supplement can only do harm. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.