I'm delighted to hear that you're thinking of doing this because I am currently on day 68 of exactly the same experiment, and I've been wishing there was somebody I could compare notes with!
At the beginning of November, in hopes of curing the migraines from which I had suffered for 47 years, I started fasting and stopped taking sumatriptan. After the fast ended I segued into a Hopkins-style ketogenic diet.
In recent years I was having migraines nearly every day. I had previously tried Atkins induction diets with and without MCT oil. I had been on a very low-carb diet for over three years. I stopped eating grains and legumes years ago. I had tried elimination diets. None of this had worked.
As I'm sure you know, a long fast induces a higher level of ketosis than any diet. That's why I decided to try fasting.
You probably also know that there is a report in the medical literature of a woman who was cured of migraine by a ketogenic diet. She was on an extreme hypocaloric diet (about 700 calories per day) for seven months. I couldn't try that because I wasn't fat enough.
Originally I planned to fast for about seven days, like you, but fasting turned out to be easier than I expected so I continued for thirty days. As the fast went on my migraines became less frequent, less painful, and briefer. The last painful one occurred on the 23rd day of the fast.
The results of the fast and diet have been wonderful. For the first time in 47 years I can say that I haven't had a painful headache in over a month. There are still some migrainey sensations but the migraine process seems to get blocked before it turns into a painful headache. These symptoms are diminishing as the days go on.
Before the fast, I was completely dependent on sumatriptan. Since day 23 of the fast, I haven't even thought about taking it. I don't need it anymore.
I'm not going to describe my fast here because it's described in detail on Paul Jaminet's Perfect Health Blog. Here's the link:
Since the fast ended I've been eating a paleo version of the Hopkins diet -- mainly tallow, meat, and eggs. Plus MCT oil which I guess isn't so paleo! :)
Please feel free to ask any specific questions you have. If you decide to go ahead with this, I would love to talk to you about it.
If I had known last November what I know now, I would have tried one more thing before resorting to a long fast. I would have bought an Abbott Precision Xtra blood meter so I could monitor my blood ketone levels and embarked upon a hard-core Hopkins diet with protein restriction and overall caloric restriction and MCT oil.
I have one of those meters now. (In fact I have three.) I believe the meter allows you to achieve a higher level of ketosis because you can adjust the diet by trial and error and measure the results.
The mistake I made in previous years, when I tried Atkins-induction diets, is that I didn't understand that protein restriction and overall caloric restriction are important factors for attaining deep ketosis.