He is malnourished and is actually starving .He does not like soy but with a vegan diet, he has to rely on plant proteins or other sources and soy is an excellent source. And only doing a liquid fruit juice diet can lead to a dangerous calorie restriction which means he is not getting enough nutrients. This causes FATIGUE, hair loss, electrolyte imbalance, gallstones, constipation, anemia, menstrual problems, LOSS OF MUSCLE MASS, and heart damage,