To build muscle and gain mass, you need to create a calorie surplus, i.e. consume more than you spend. Moreover, you will have to consume about 15-20% more than the norm.
To do this, you will need to eat often - 5-7 times a day - and consume a large amount of food. The emphasis should be on complex carbohydrates - buckwheat, oatmeal, quinoa, pasta from t / s wheat, as well as proteins (you need about 2-2.2 g per 1 kg of body weight per day) - chicken breast, lean turkey, veal, beef , baked fish, cottage cheese, legumes, soy products.
Unsaturated fatty acids are also needed, they can be obtained from flaxseed, olive oil, fatty fish, avocado.
Ie. in general, you can eat regular food and be pumped up, but it can be difficult to absorb large amounts of food. It is not so easy to eat the right amount of calories per day. Therefore, they resort to sports supplements.
For example, it is easier for the body to digest and assimilate a portion of protein than 200 grams of chicken. In addition, if you work or study, then you will need to carry 3-5 trays of food with you and constantly look for a refrigerator. While a serving of protein or a gainer (if you are very thin, it is better to choose it) takes up little space, it can be quickly and easily mixed in a shaker to make a healthy meal replacement.
I fully support the previous comment. + include coffee in the food, just not the clay that simply stains the water, but the normal custard, like all burnt foods, it disperses bile and, accordingly, improves appetite, drink it while eating. yeast and, of course, calmness, complete internal balance. You can't go far with nutrition alone
In short, there is often a lot. 6-7 meals a day. Cereals, meat, fish, eggs, fruits, vegetables, dairy products. When you plow hard your appetite will be good.