"A multitude of patients have come to us for pain between the shoulder blades or in the upper back. This area of the spine that starts just below the neck, and ends at the bottom of the rib cage, is called the mid-back."
"One of the most interesting and baffling causes of mid-back pain is from the blood-sugar control system. Because the nerves to the organs of blood-sugar control (pancreas, liver, and adrenal glands) travel out from this part of the spine, a person’s dietary error may trigger this type of spinal pain. The other day a patient reported a stabbing mid-back pain. On inquiring, she told us of eating her way through a whole bag of candy in one sitting (just before the pain started). Excess carbohydrate (sugar or starch) overload can cause this area of the spine to subluxate (go out of place, and irritate the adjacent nerves). The typical location is right around the center of the back (at about the height that a bra strap crosses a woman’s back)."
http://www.livestrong.com/article/532363-atkins-diet-back-pain/ This article was written about the high protein/low carb of the Atkins diet, and I can't agree with all that is in it but this might be food for thought. "As you deplete your carbohydrate reserves, you also lose your ability to store as much water. Each gram of glycogen that your body retains stores approximately 4 g of water. If you start to dehydrate, you might start to cramp." "Your muscles consist of roughly 75 percent water by total volume, so nourish them appropriately. If you experience dry mouth on the Atkins diet, you need to significantly increase your water intake." I personally know I don't drink enough water. That alone might not help. "Three minerals primarily affect muscle cramping: calcium, magnesium and potassium." so also could be related to mineral deficiency. I know I limit myself on types of foods, and do not eat fruits because I have a fruit intolerance so that might not help me. Somewhere else I saw it could be a vitamins D deficiency. This might all be shooting in the dark but also decent advice either way.
I had severe upper back pain for the first two days of fasting. I thought it came from lying on my side and reading in bed, but on the other hand, I have done this often without causing back pain. I think the explanation offered in the chiropractic article is very interesting: "One of the most interesting and baffling causes of mid-back pain is from the blood-sugar control system.". As the article hints, what I call the upper back is in their professtional terms the upper mid back. After these first days it went away. This corresponds with the onset of ketosis.
I am fasting and having a lot of pain. I believe this is a combination of muscle dehydration and low potassium. Low potassium causes cramps. Over the counter Potassium supplements are worthless (3% of RDA per pill) and getting a prescription for potassium is not practical. Potassium is available in adequate amounts in salt substitute, though. One tablespoon of NuSalt is 75% of RDA of Potassium. It tastes lousy but if I get a spoonful of that, then my back aches go away within about 20 - 30 minutes. Beet greens is another good, low carb source of potassium.