If your goal is to build mass and muscle size. The type of physical activity: High intensity, such as iron exercise, is recommended to eat at least three to four hours before high intensity physical activity.

In order for the body to benefit from the energy that is made up of food, it must be transformed into an ATP so that the body can benefit from the energy of food. It's stored in most cells, especially skeletal muscle cells.
Without food, the ATP will be low, so the body will not have the energy to carry weights and sustain physical activities.
Even with ATP and CP energy sources, the body will be limited to 10 seconds. The body will then transfer to glycogen the athlete's energy source in high intensity exercises. If glycogen is low in the body due to lack of food before physical activity, the body will not be able to continue the training quota for a long time or to carry weights.