Weight-lifting is a great way to lose fat. It’s also a great way to build up muscle. Resistance training, often called strength training, has been shown to build and maintain lean skeletal muscle which leads to loss of fat. When you have stronger muscles, you have a faster metabolism. This stems from the improved Insulin Efficiency created by lean muscles. By incorporating strength training into your workout routine, especially in conjunction with cardio and core exercises, you keep your whole body operating more efficiently, i.e., more food becomes energy and not fat.
One study examining what happens when we replace fat with muscle found that losing 4 pounds of fat and adding 3 pounds of muscle increased participants metabolic rate by 7 percent, meaning that they burned 120 calories more per day than usual just going about their normal business.
120 calories may not sound like much per day, but it adds up real fast. A single pound of fat is comprised of 3,500 calories. You burn 3,500 calories; you lose a pound of fat.
Extrapolating that fact out, burning an extra 120 calories over the course of a whole year means: 365 x 120 = 43,800 calories, i.e., you lose 12.5 pounds of fat.