Getting on LC can cause a little loss of energy and stamina at first, but just keep it up and do whatever exercise you can and before you know it you'll be feeling normal again, or in my case, better than "normal".
It takes a little commitment, but after your body quits complaining about no blood sugar, you'll be fine.
I had a physical 2 weeks ago and didn't tell them that I was LC'ing until after the blood work came back. They told me that EVERYTHING looked great and that it couldn't possibly be better.
No hint of:
diabetes (which runs in my family)
Kidney disease (which doesn't run in my family)
or any other diseases incident to age.