A Black Cow is chocolate ice cream dissolved in coke up to the point of saturation, turning it into what I in Conn called a milk shake, but now in Mass must call a frappe. It is the most yin substance I can consume since I do not drink or smoke.
Smoking tobacco is yang by the way according to Zen Macrobiotics, but it did not relieve my sciatica pain. Here is a link to the guy Michio Kushi that changed my diet:
I once had a boss who was a marathoner and always ran on the same side of the road. He wrote to Dr Sheehan's Runner's World column and sought advice for a problem he was having. Dr. Sheehan surmised that he was running always against the traffic and advised him to run on exactly flat surfaces or at least alternate the slopes of the running surfaces. My boss's problems disappeared in a week.
I drink Black Cows for satisfaction. If I drink too many and do not racewalk off the yin effects by walking 10-15 miles at a 10 minute/mile pace, I get systems of arthritus. It might have something to do with being 65 as well.
Anyway, when I had sciatica, I was 5'9", still am, and the diet brought me from 160 to 140 without exercise. Now I am 180 and struggling to get my weight down, and my nerves thin. Black Cows do not help, especially just before bed. I wake up with a sore back.
So at 5'11" and 240, I suspect you are still with enlarged nerves. I am not sure what the scaling is with height, but if you take this diet seriously, you should drop below 200 and best of all your pain should disappear along the way. It worked for me. But you have to give up alcohol, coffee, fruits, dairy products and at least red meat. It takes a pretty desparate person to do that, as I was. But any shift in your diet in that direction should help.
The above link has some indication of how to proceed. I did not see a list of all foods with their corresponding yin/yangness, which is very instructive. But the Kushi people can sell such a list if you cannot find one for free on the web.