Peanuts contain protein, fat and carbs. A bowl serving (75g) contains 18 grams of protein, 13 grams of carbs and large amounts of unsaturated fat. They also contain higher amounts of the amino acid leucine than many other plant products. Peanut butter is also a good source of monounsaturated fat and antioxidants. Just one tablespoon of peanut butter has four grams of protein, making it a good source of protein for building muscle.