Mick Jagger recently posted a video showing him bounding about like a young gazelle on stage during the Rolling Stones' current Hackney Diamonds tour. He'll be 81 in four days.
How has he managed to remain so limber and energetic? For one thing, physical exercise has always been important to him. His father, a physical fitness instructor who lived to 93, likely influenced this. Here's a 1959 video of a pre-famous 15-year-old Mick demonstrating his mountain-climbing skills.
Jagger's probably having too much fun traveling the world and performing, but I think he could write a bestseller that lays out his diet and fitness regimen.