Jim says this works for a few key reasons. First of all, you see the data. "So many people over the years have said to me, 'I really don't eat that much; I don't know why I've gained so much weight," Jim says. "But when they start keeping a food diary, the reality of what they're putting in their mouths—the sheer volume of what was previously inhaled unconsciously—is right there in black-and-white. It's astonishing, it's enlightening, and it's indisputable.