Are potatoes the root of all evil?

The chiropracter sorting my RSI said to me that he wanted to test whether I was sugar sensitive, and that I can’t physically deal with all the stress I’m under at present.  Tell me something I don’t know…

I should explain, last week I had the migraine from hell.
I’ve had migraines since my teens but far more of them following a car crash I was up to one or two a week. The headache clinic at St Georges hospital in London helped sort it out a bit and then a prescription drug keeps it under control, and I’ve managed my migraines relatively successfully for a year or so.
But this one snuck up on me. I’d taken the drugs for it a few days earlier when I thought it was coming, but it arrived without warning on and I couldn’t even get out of bed with the light sensitivity and nausea.

I hadn’t mentioned to the chiropractor but as he felt my neck he asked whether I’d had a really bad migraine this week as I was holding my head as if I had.
After the various cracking things that help sort it all out, he pushed two points in my stomach which were very painful (apparently this is an adrenal acupuncture point).
He asked about the stress I’m under at the moment and established that this was very high indeed and multisourced.

Now I’ve been trying unsuccessfully to lose some weight for quite some time and I’m increasingly convinced that it is part of my body’s reaction to stress that I seem to cling onto the weight even when doing the things that have in the past helped me lose weight.

We talked about this and he tested my sensitivity to sugar – I’m not to my knowledge diabetic and can think of many reasons to cut back on it but “sugar sensitivity” is a new one on me.
But having seen myself that I could not perform the same exercise as well after sugar as before, I’m beginning to think that Sportacus has a point.

And in order to help control the migraines further (as well as help kickstart weightloss) he suggested avoiding sugar – at least until my next appointment in a month – and cutting out potatoes, replacing them with sweet potatoes.

So given there’s so much sugar in everything, this is an interesting challenge…
Why are potatoes so bad for you?
I know that the starch has something to do with it.  And  they get a separate points value at Weightwatchers rather than being part of the free vegetable allowance.
But do they contribute to my migraines?
Are they in fact the root vegetable of all evil?

Not convinced but I’ll give it a go – but I reserve the right to go a bit Rincewind about them… within limits of course…