Could you tell me what happens with excessive protein in the body?

Depends!: If on a low carb diet, burned as fuel to produce glucose by the liver, and used as building blocks for your bodies protein, isnce it is broken down to essential amino acids. If on a normal diet, there are 4 kcal per gram of protein. And it will count toward your total caloric intake and cause weight gain, if it exceeds the calories spent by basal metabolism and your activity.