When you do weigh yourself, remember that sustainable progress is usually fairly slow. Depending on how many calories you cut out of your diet and how much exercise you're getting, 1-2 pounds per week is a reasonable goal. This doesn't mean that there's nothing to be gained by doing a fat-loss focused workout program that only lasts a few weeks, though. On the contrary, as fitness coach Sohee Lee writes, many researchers believe just three weeks is enough time to create lasting healthy habits. In reality, nothing could be further from the truth.