Muscle building can be a confusing concept, but here are some key ideas to help.
1. Muscle is a fiber composed of protein. This means that muscle cannot turn into fat, which are cells composed of lipids.
2. Muscle fibers grow in mass, and volume, based on damage done to the fibers. For instance, low impact tension exercises will cause the fibers to become more dense, but not quite so massive as do heavy, load bearing exercises like weight lifting.
3. To repair damage to the muscles, and gain mass, an individual needs to intake an increased amount of protein, which is composed of amino acids. Be careful if you decide to increase your protein intake because it can have adverse effects on your digestive system.
You can counter act this by increasing your daily fiber intake.
4. The body produces HGH (Human Growth Hormone) naturally. While higher levels are produced during childhood, adults can help to facilitate natural production by ingesting protein after an exercise routine. See this article from the JAP
Ingesting other foods after a work out will force the body into an energy recovery stage (one useful for high impact cardio work outs like a marathon), but will not aid in building muscle mass nearly as well as ingesting protein. Save your carbohydrates for early mornings, or mid day when you feel a little sluggish.
5. Pounds are gained by ingestion of calories, the unit of energy used or stored by the body. Eating a 500 calorie candy bar cannot make you gain 5 pounds. Because the bar only weighs about 5 ounces, that is the net weight you will gain before digestion, however, because the calories derived from the candy are mostly from fat, you will store rather than burn those calories.
6. One pound of weight gain is equivalent to about 3,000 calories. Most diets are based on a 2,000 to 2,500 calorie intake, but adding exercise to your daily life will cause the body to burn more calories than a sedentary life. If you move more, eat more, but eat more protein to gain more muscle mass.
Everyone's body is different. Some people gain a lot of muscle mass in their legs, others grow their chests, or arms easily. Experiment with different exercises, but most importantly, try to find something you like. Refrain from turning a fun hobby into a chore. You'll go farther.
Check with your physician before starting a new diet or exercise program.