In the same issue wherein Gary Taubes discussed the evils of sugar, the Times ran a couple of other interesting articles on fitness and health. One was on sleep (get enough) and the other on the best form of exercise. The linked article discusses the best form of exercise. The winner: HIT or High Intensity Training. In other words, go hard, very hard, for brief spurts and lightly in between, whether you talking intervals of minutes or days. If you've read Art De Vany, Dr. Doug McGraw, Mark Sisson, or others in the Primal Community, the answer will come as no surprise. Even before this article I'd incorporated this regimen into my time on the stationary bike, and when weight training (high weight, low reps). Also, think of basketball, a form of play with constant movement punctuated by brief intense spurts. Are any athletes more fit that basketball players? It kept me reasonably fit for many years.
The runner up? The squat. "Air squats" as Tim Ferris calls them. They do well in a pinch.