My friend was given bad advice by a consultant. She ended up on SS for about 17weeks, then did a week of SS+ and went back to it for another 6 weeks.
Her hair fell out. It would just come out in big clumps when she just put her hand on her hair. After about 6months, it has only just started to grow back, but it is much much thinner.
Her stomach was unable to cope with any food - if she ate anything the pain was unbearable.
There were some other side effects but I can't remember them now. These were along with the usual - constantly being cold, not being able to remember anything, lack of concentration, lack of energy, dizziness, etc.
The guidelines are there for a reason. As long as you follow them, you'll be absolutely fine as Cambridge is a good diet.
It's a warning to those tempted to disregard them though!