Hi, i'm 26/m, 79 kg and 191cm height, i exercise 4times a week at gym, can brewer's yeast help me gain weight? how many of them i should take daily?

Adjunct only: This is a nice natural source of vitamins. Don't spend much money on it. I am very glad you are exercising. Your body will look great with or without a lot of mass -- many women prefer a lean and trim man. If bulking muscle is what you want, consider creating. Aerobic exercise and moderate sensible eating will give you the great muscle definition that most men seek. Keep up the good work.