<human>:  Does muscle building require a caloric surplus, or just extra protein?
<bot>: Muscle building typically requires a caloric surplus in addition to extra protein in order to increase muscle mass. The caloric surplus can be achieved by increasing the amount of calories eaten, and by providing the body with the necessary macronutrients, i.e. carbohydrates, fats and proteins. Consuming extra protein, in the form of supplements and/or a diet with high-quality protein sources like lean meats, will help to ensure that muscles get the necessary building blocks for growth and repair.