Congratulations on considering a change that may help you regain your energy- it's certainly worth a try even though you are already in good health.
Here is a website of a lady who is over 60 and thrives on a mostly primal type lifestyle. She eats grains but you can of course just ignore that:
Nancy Deville | Author of Healthy, Sexy, Happy, Death by Supermarket, and Karma
Marilyn Diamond, the vegetarian who wrote Fit for Life, went more primal in her 60s also and has a new book coming out, you might want to check that out. She's a bikini model now as the result of being more primal- it's never too late to get healthy.