Experts are not sure of the reason for the insomniac effect and fasting, but it is common. For some (but not all) it could be your system getting rid of the caffeine stored in your body. Also your body is much more sensitive during a fast which is why you should not use caffeine and drugs are not suggested since it may affect you as if you took 4 times as much. Remember how food lessens the effects of alcohol.
Using an enema during a fast is optional. At the end of the fast, you will get rid of all that stuff and your colon will work better than ever. I prefer to get rid of that stuff with an enema rather than store it for the whole fast. At the end of this fast, you will be a new person and it has an anti-aging effect on you. This site has info on losing weight with fasting by an M.D. Plus it has quotes about fasting by 17 different MDs plus what New England Journal of Medicine says about Fasting for weight loss and lemonade diet or lemonade fast.