What will eating a low calorie, high protein diet do to the body?

Depends on the exten: of the change from an average diet. normally we need about 10x weight in pounds to maintain weight. 10-20% below that, you'll lose weight. If you don't do muscle stimulation (weight lifting) it will be mainly loss of muscle. 50% less than required calories could cause metabolic serious problems. Protein causes a bit more kidney work. W. normal kidneys, doesn't matter.