A.J. Jacobs has built a career out of exploring life in a Plimptonian manner. Unlike George Plimpton, though, who positioned himself as a fish out of water in "Paper Lion" and "Out of My League," Jacobs prefers to become one with the water, immersing himself in living biblically, or in outsourcing every aspect of his life, or, in his newest book, in becoming the healthiest person on Earth.

(A tall order, when you see his saggy "before" picture.)

Jacobs' light touch camouflages the impressive amount of research that goes into each chapter. He reads books and medical reports, interviews experts and scientists as well as enthusiasts on the fringe, then tries everything himself. He brings a skeptic's eye to each point of view, but he remains respectful of even the wackiest ideas.

Over two years, he works on his health, taking it body part by body part: Skin. Eyes. Heart. Lungs. Feet. Unmentionables. He experiments with caveman diets, runs barefoot, rigs up a desk at his treadmill so that he can write while he walks. He wears noise-reducing headphones to protect his ears and reduce stress. (But when he tries to add a helmet to protect his cranium, something has to give.)

Yes, the results are funny, but this is, at heart, a serious book, with an underlying poignancy: As Jacobs works to get healthier, his beloved grandfather begins his slow decline, reminding us that no matter how healthy we are, it's all going to end the same way.