I have significant knowledge of fasting for issues such as diabetes, auto-immune disorders, etc. I regularly read blogs and academic papers on the issue so it makes sense to me that this would be significant as it sets off an avalanche of cleansing processes:
- It temporarily shifts a lot of your hormones during the fast. Insulin, glucagon, SHBG, etc etc.
- It purges fat cells and in particular it purges organ fats more effectively. It's widely recognized in medicine that organ fat is worse for you than subcutaneous fat, so purging that more efficiently will yield you long-term hormonal advantages that last after the fast.
- Separately a lot of toxins are stored in fat cells, so getting rid of them is good for you.
- It reduces inflammation. Mine dropped by over 80%.
- Once that's done, your body is leaner, it doesn't have as much aromatase and other bullshit flowing around, you're in much better condition for the following regimen.
- It helps heal the brain. The brain does different things on ketones than on glucose, and for that you have to wait at least three days. We know that ketosis cures epilepsy -- the Romans knew that. It also seems very successful in combatting depression.
- It stimulates autophagy which begins 18 hours into a fast, a real fast not a fake juice fast. Autophagy is the process whereby your worst cells and worst mitochondria are preferentially catabolized.
- It decreases microbial load in the digestive tract, which helps heal your microbiome.
The fact that you fainted on day five means that you didn't know what you were doing. I have done many fasts, including multiple 7-day fasts and have never fainted. Try doing a proper calorie-free fast rather than a juice fast, so that you actually get ketosis, abdominal fat reduction, and autophagy. You can supplement with salt (1 teaspoon a day) to decrease the risk of fainting. In the first couple days, add a few tablespoons of coconut oil to help smooth the transition.
Here's a decent documentary that you can watch:
http://fastingmovie.com
For motivation look up interviews with Doctors Alan Goldhamer, Valter Longo, and Jason Fung who are experts on fasting.