The first link I found, which was fairly typical was this: http://www.diagnose-me.com/cond/C240808.html which talks about carbohydrate addiction. This seems to be lead to/reinforce insulin resistance and is also linked to low serotonin, although I'm not clear on what the link is between those two. More hunting around suggests links with SAD and possibly atypical depression (which also has possible links to thryoid issues apparently), both things I have show signs of at different times.
It looks like the most sensible course to reduce insulin resistance in the long term would be to try a low GI diet for a while. A lot of the foods I choose seem to be high GI as well (cornflakes, for example, which is one of my favourite snack items and jacket potatoes, my regular lunch), which is an interesting indicator. Low serotonin levels can be combatted with lightbox/daylight lamp treatments (can you get low energy daylight bulbs?) or supplements so I guess a shopping trip is in order.
Its interesting because it's another way in which a lot of my issues link together. Serotonin is involved in body tempurature regulation, mood and sexuality which are all issues for me. Looking at this and the thyroid stuff earlier in the year make me think about what a complicated interrelated machine the body is - all these things link together and interrelate in such complicated ways and it's so hard to tell exactly what part of the system is not working as expected.