Let’s destroy the assumption. You cannot! Let me explain. There are a lot of factors that come into play when trying to gain muscles .
The first and most important factor is the genetic body type you have . There are three body types and the mesomorphic body type has an evolutionary advantage when it comes to building muscles. Although mesomorphs are physically blessed, their negligence can be their downfall. Endomorphs gain muscle easy but the same goes for fat. They have to work to keep those muscle cuts. Just look at The Rock (He’s an endomorph.) The third body type ectomorph has the hardest time gaining muscle. They tend to remain thin all their life and have to work really hard for a good body.
The second factor that matters is your exertion level. Sitting at a desk job for 9 hours isn’t enough physical exertion to become muscular. Fingers working on the keyboard all day will give you finger biceps, not arm biceps. The only people who gain muscle through their regular exertion are miners and construction workers whose jobs naturally involve a lot of exertion. People whose jobs involve traveling a lot also have this advantage. Since most people in this world have desk jobs you need to find a way to exert yourself physically. That extra exertion is called ‘working out’. Working out can be anything from an outdoor sport to jogging a mile at the park.
The third factor is your diet. Now despite all the bodybuilders shouting “Protein!” let me make it clear ‘It won’t matter if you don’t exercise’. Eating just protein-rich foods won’t build up your body. Avoiding fatty foods also isn’t the solution. Skipping meals is the worst thing you can do. Some think that eating whey every day will help build muscle. It will, but over your FAT. That is a disastrous prospect and burning fat is essential for becoming muscular. What you can do is eat properly and don’t avoid junk food but eat it in regulated amounts (Enjoy the Fries!).
GO NOW! Get on that treadmill and then bench press those weights!
Muscles are built by lifting weights or working out on a regular basis. If you want to continue to build muscle, try lifting more weights or doing higher repetitions. The more muscles are worked, the more they will grow. You can help to build muscle by making sure you are getting the right nutrients as well.
Make sure to eat enough protein and carbohydrates to keep your body fueled. Also, make sure to give your body enough rest to recover and be ready for the next workout.