If someone were anorexic, could they prevent hair loss by just eating a small amount of protien?

No: To avoid hair loss, one needs to follow a balanced diet. Vitamins, carbohydrates, essential fats, and minerals are necessary in addition to protein for a balanced diet. One also needs to get enough calories in his/her diet to maintain hair growth.

No: Eating disorders like anorexia are extremely stressful to the body, by depriving it of essential nutrients. In addition to not getting enough nutrients to form the building blocks of hair, the whole body is going through stress; any illness or extreme stress can cause hair loss, called telogen effluvium. Our bodies need well balanced nutrition for every system to function well.