WWII concentration camp victims, who were purposely being starved to death, received 1300 calories per day for light work, while those at hard labor received 1700.

You could try to think about what parts of your body are still operational, and work those. It's possible to get an aerobic workout without even using your legs. By what you say, your legs still work. You could probably ride a trainer or exercise or spin bike. If I have to go more than 3 days without cycling, my ability begins an obvious decline. I figure 3 days to regain the fitness lost by every day off over 3. While a great generalization, this is not too far off. Sorry for your misfortune! "One accident can ruin your whole season."