I think that's too heavy duty of a fast for someone with his history. I would try to eat a lighter diet like smoothies, salads and good sources of protein maybe for a couple of weeks but just water and his health issues. That sounds VERY concerning to me. I would contact his Dr. or a ND or holistic nutritionist to help come up with a plan or start with like I said a less intense fast. I know two people who were overweight and died making healthy Diet changes and exercises. They just really shocked their body I guess. Not worth the risk IMO.