Wt. Training, & food. An 18-21 year-old male (college aged) is not going to grow any taller (growth plates have fused). Choosing proper designs of clothing and shoes can help one appear taller. Good posture helps also. To increase muscle mass, one has to work out against resistance (with weights). This exercise will increase daily calorie needs, so he must eat more of the healthy, balanced diet he should already be on.