Do you weigh the same that you did a year ago? 10 years ago? Even if the rest of you is getting better with age, there's one part of ourselves that definitely isn't — our metabolisms. The result: an average of a gain of a pound a year after age 20. While a pound a year doesn't sound like much, it can lead to being overweight later in life and increasing your risk of diseases like breast cancer and stroke. Here's what you can do to stop the weight creep.