In this tutorial, we learn how to gain weight with a fast metabolism. If you have a high metabolism, it may be difficult for you to gain weight. Eating more just isn't enough if you want to gain weight, you want to change your habits that will change your hormones. Testosterone has an anabolic or growth effect in your body that promotes muscle strength and breakdown. Include fatty acids in your diet, which are healthy fats in avocados, fish, oils, and nuts. Also, lift heavy weights and use as much muscle as possible. Then, you will need to limit alcohol, and make sure you are eating enough protein in your diet!