Ferriss tracked the progress of approximately 3,000 of his readers as they tried to take on six diet and exercise habits prescribed in 'The 4-Hour Body' and discovered that when they tried to do too much at once, they ended up doing nothing at all. Ferriss concluded that adopting several new behaviors at once creates an unsustainable lifestyle. "You find people who want to burn fat so they decide with a New Year's resolution that they want to do an hour of exercise or more a day," says Ferriss. "But with the first unscheduled travel or problem with the babysitter, their program becomes impossible and they quit altogether." This realization inspired his fitness fundamentals, 4 simple exercises that require nothing more than a bit of space.