Knowing how many calories you're taking in and using up is one way to keep you honest about weight loss. Though it may seem tedious, keeping a food journal works because it helps keep you accountable for every bite. In fact, one study found that those who logged what they ate six days a week lost twice as much weight as those who only kept track of a day or less. In order to lose a pound a week, you need to cut 500 calories a day — 250 through exercise and 250 through diet is a good breakdown. Just be sure not to dip below 1,200 calories, since not consuming enough calories will make your body hold onto fat.