Calorie consumption: basic metabolism (energy to maintain basic physiological activities), life and exercise metabolism (energy consumed in daily life and training), and food calorie consumption (energy used to digest food).
Heat source is very important. The calories provided by carbohydrates can effectively help gain muscle and weight, but fat can't.
We can start with the source of calories: protein provides raw materials for muscle growth, and carbohydrates provide sufficient high-quality energy for muscle growth. So we both ate enough, and the effect came out. A nutritional intake formula suitable for weight gain: per kilogram of body weight per day 1.8g protein and 6g carbohydrate. Take a 60kg lean person as an example, that is, you need to consume protein 108g and 360g of carbohydrates every day.