Purpose of review: To highlight the underexposed but important role of protein in food intake and body weight regulation.
Recent findings: Protein plays a key role in food intake regulation through satiety related to diet-induced thermogenesis. Protein also plays a key role in body weight regulation through its effect on thermogenesis and body composition. A high percentage of energy from dietary protein limits body weight (re)gain through its satiety and energy inefficiency related to the change in body composition.
Summary: Protein is more satiating than carbohydrate and fat in the short term, over 24 h and in the long term. Thermogenesis plays a role in this satiety effect, but the role of satiety hormones still needs to be elucidated. On the short-term 'fast' proteins are more satiating than 'slow' proteins, and animal protein induces a higher thermogenesis than vegetable protein. In the longer term the higher postabsorptive satiety and thermogenesis are sustained irrespective of the protein source. High-protein diets affect body weight loss positively only under ad-libitum energy intake conditions, implying also a decreased energy intake. Body composition and metabolic profile are improved. Additional protein consumption results in a significantly lower body weight regain after weight loss, due to body composition, satiety, thermogenesis, and energy inefficiency, while the metabolic profile improves. Implications from these findings are: for practice, recommendations for increasing the percentage of energy from protein while reducing energy intake; for clinical research, assessment of the paradox of increasing the percentage energy from a highly satiating macronutrient; of the potential roles of protein in a negative and positive energy balance; assessment of possibilities of replacing dietary protein by effective amino acids or peptides that may show a similar impact on body weight regulation.