2-how to build muscles without getting fat?

Muscles are proteins, which means that to understand how to build muscles, you need to understand the proteins.

THE PROTEINS

What is (definition)
A protein is a macromolecule composed primarily of linear chains of amino acids.
There simple protein composed only of amino acids and their derivatives. Also, the conjugated proteins, which are formed by polypeptide chains and prosthetic group.


Functions of proteins
They play a very important role in our body, they provide materials for both the construction and the maintenance of all our organs and tissues.
The proteins may be of vegetable or animal origin. In the first case, they are incomplete because they are poor in variety of essential amino acids (those which the body is unable to produce). Since the protein of animal origin, it is considered complete to contain all the essential amino acids.

Importance
As already mentioned above, proteins are of utmost importance to our body for its construction and repair function. They also participate in the formation of hormones, enzymes and antibodies. With these few examples, one can already get an idea of ​​how much they are essential to our body.
When we eat proteins, they are broken down during the digestion process, and subsequently absorbed by our cells, which again the break, turning them into amino acids. These amino acids are used by our body where they are needed.
For example, if the skin of a person is unbalanced by the lack of amino acids, foods rich in proteins and proper intake of water would be beneficial to recovery. This is true not only for skin, but for the whole body, because, as we have seen, the amino acids are builders and repairmen.
proteins
Okay, now that we know the definition, the function and the importance of proteins, we need to understand how to build them!
To build a protein you will need amino acids and energy to bind them together, to get those you will need mostly two things: Proteins/amino acids and carbohydrates/sugars. But aren't the carbohydrates responsible for making me fat? Yes and No, carbohydrates main function is to serve as an energy fuel for the body. "Carbon atoms, hydrogen and oxygen combine to form a carbohydrate or a sugar moiety" (look at picture below). The energy is a result of usage of the calories, you get those from the carbohydrates and sugars for example, calories are present in the food you eat. After the calories enter your bloodstream, this fuel is burned in several metabolic processes. This includes your muscle activity, digestion, breathing, brain function, hair growth etc. The basics of survival, to summarize.
But sometimes we consume more calories than the body can burn. When this happens, our body thinks, "Hey, I do not need all that energy now. I'd better store it in case I need it later, right?" So begins the miracle of fat. Your body takes those calories left over and keep the fat cells. They expand as they collect more fuel, and shrink when you use some of that energy.
This explains not only how you get energy but also how you get fat! Now you might be thinking "But that didn't quite answered how carbohydrates help to build muscle instead of protein..." But it did! As I said before, lipids are only formed if you don't use all the calories you ate, and building up muscles use energy (that is going to come from the calories), which means that if you eat just enough calories to supply the body activities, you will not turn it into fat.