I believe, all that matters is strength and quality of tissues. Before engaging in that journey, many (most) ppl have water retention due to toxicity and low-quality tissues in different places. Surely - you don't want to gain weight with having this back. You may want to gain through muscle work, but it is more like a vanity goal, if your BMI is already normal.
For certain things, long fasts are necessary. Like in my case. Dan has detoxed for years, and may have not replenished for very long time - I believe this is what he was talking about. He did 10 days WF the longest, I believe. Lou has done 45 days organic watermelon, followed by 1 month just by organic greens - this is what helped him get rid of a tumor .. and has been raw - the activated, living food way - ever since - this is what helped him not to get any disease or the tumor back for decades since. An important detail is that he was 27 year old when he did the Watermelon fast followed by leafy greens. At that age everything is working faster and fuller, for s.o who is 20 years or 30 years older the strategy may need to be different. But surely would not hurt doing what he did. BTW speaking protein (rather amino-acids) per calorie ratio - the Watermelon is not worse than milk, but better since it is easy to digest and is cleansing.
Both Lou and Dan are talking in this video about 100% raw Organic Living or culturized food.
For my part I am not sure I will be able to commit 100% on the raw organic living foods - question of timing, environment and finances. Therefor I choose to aim for a long fast that will certainly do a better job than many short ones. BTW my BMI is 19.7 and I expect to get down to 14-14.8 at the end of a long fast. Then I may think of another long one after I get back to at least 18-19.