Intermittent fasting (IF) can cause trouble for people who already have issues with their blood sugar. IF is where you go for various amounts of time without food. The easiest IF routine is to fast all night and then not eat until 12 the next day. IF is very popular with the Paleo and Primal eating communities and I think for some people, in some circumstances, it can be fine even beneficial. But for others of us, it needs to be put into the context of our pre-existing conditions.
It's important that if you think you have any blood sugar issues that you determine "what is going on in there" (as my teacher Andrea Nakayama would say). Many conditions from PCOS to high LDLs stem from blood sugar problems. Get your fasting blood glucose (FBG) tested at your doctor's and buy a glucose monitor and test at home. From here you can learn how certain foods and certain meal times effect your blood sugar levels AND your insulin response to them. If your blood sugar is rising above >150mg/dL three hours after a meal, you may have some insulin resistance developing and you should consult with your doctor.
What I found with myself was that IF exacerbated my blood sugar issues. As I practiced it, my FBG started to rise no matter how low my daily intake of carbs was. Also how responsive my body was to the sugar I did eat also began to decline. This is not a good trend. I have a suspicion that women's bodies handle the stress of IF differently than men's. For short term gentle detoxes, IF may pose no real danger for people. But for others care should be taken. And how do you know if you have blood sugar issues? Some symptoms might include: headaches, dizziness, fatigue, night waking, sleepy after eating, massive cravings, and shaking when you have gone too long without eating. All of these should be shared with your health care practitioner to rule out anything serious. Blood sugar regulation is a very important part of health. And it is the cornerstone to good preventative care.