Protein is an essential macronutrient in the human diet. In addition to providing essential amino acids to the body, protein has also been linked to inducing the feeling of fullness and satiety. Different sources of protein are traditionally used in the human diet and offer varying amino acid composition. This chapter will summarize work on the implications of the amount and type of protein in the diet to promote the control of hunger and fullness (satiety). Furthermore, evidence regarding the short-term implications of high protein diets on colonic microbiota, fermentation and ultimately intestinal health is presented.