This formula has never failed to work for myself or for any of my nutrition-coaching clients. I always lose 6-10 pounds with this plan (once I lost 14 lbs. between Sunday and the following Saturday). It's almost a drug-like effect. I've never had a problem with cramps. A word of warning: This protocol is designed for serious bodybuilders to achieve a temporary peak in cosmetic appearance for the day of a competition. If you have any metabolic disorders or health problems I wouldn't recommend this. Check with your physician if you're in doubt - but if you do, your doctor will probably have a fit: this can't be good for you and you'll feel like crap the whole week, but damn will you be SHREDDED!
If one is on a ketogenic or extreme "low carb" diet however, the body will need to utilize another source to synthesize glucose from. Since glycogen levels are low on a ketogenic diet, the body will actually convert amino acids to glucose and this glucose will be used in the anaerobic pathway to produce ATP. These amino acids will come from dietary protein, amino acids from the cellular amino acid pool, and from muscle tissue. The latter situation is where one would experience muscle loss. Dietary protein would be sacrificed for ATP production and the depleted amino acid pool would not bode well for protein synthesis rates, thus causing a net loss in muscle mass.