Studies show that the more you pay attention to your body's statistics, the greater the chance you'll adopt a healthy lifestyle. This idea underpins the Quantified Self movement, in which adherents track everything from caloric output to selenium levels. The mere act of weighing yourself daily makes it more likely you'll shed pounds, according to a University of Minnesota study. Keeping a food journal makes you eat fewer fatty foods, according to another study. And pedometers make you walk more.