For me, I think it was a mixture of chronic stress and horrifically bad (mal)nutrition over a period of many years. I had a ridiculous sweet tooth and would frequently consume 100g or more of sugar in a single sitting, even after a starchy meal. The stress was probably a result of the sugar and omega-6 overload. It wouldn’t surprise me if metal toxicity and such is linked in with this too. How does a beaten up, malnourished body that’s barely functioning on all levels properly detoxify itself?
If it wasn’t for the painful symptoms in my arms, I’d still be considered “normal”, despite surviving on little more than crisps, pizza and chocolate while at uni. Relying on conventional health care did nothing but crush my motivation and waste a big chunk of my youth. I guess, like Chris, my body has finally forced me to make a lifestyle change.