The rise in cases of obesity in Western nations has increased interest in the dietary causes of satiety. Generally, mixed meals tend to cause satiety when a particular bulk of food has been consumed. And for this reason fibre can decrease appetite and energy intakes. However, when the macronutrients are isolated, protein is able to cause significant reductions in appetite, unrelated to the actual bulk of food. This may result from a decrease in rate of digestion, caused by protein being held in the stomach while acid and enzymes act to hydrolyses it to constituent amino acids and short peptides. This delay to gastric emptying may be a primary driver of satiety in humans. Support for this theory comes from the numerous studies that have shown weight loss with high protein diets. Delaying gastric emptying may also decrease carbohydrate absorption rates, which decreases glycaemia.
Researchers1 have investigated the benefits of protein to satiety using three studies that were performed on 20 healthy subjects who ate various beef-based preparations (roast beef, boiled beef and canned beef). Initially subjects were either fed a beef pre-load meal followed by a test meal or both meals together. Eating the beef pre-load meal caused a significant reduction in total energy intake and weight (bulk) of food. When subjects were given ad libitum access to one of three beef preparations roast and boiled beef produced similar intakes of food, but canned beef was eaten in greater quantities. When the beef products were served with a fixed amount of salad, satiety was reduced in all three groups. The degree of satiety was dependent on the degree of satiety induced, with large portions of beef most effective at decreasing satiety throughout the day.
Interestingly, the subjects in this study ate canned beef in higher amounts than boiled or roast beef, when given ad libitum access, despite having the least pleasurable taste. This may related to the higher water content of canned beef, resulting in the subjects consuming more product until a set amount of protein had been ingested. The supports the contention that protein content of the stomach is a direct determinant of satiety. The ability of beef to decrease subsequent energy intake if given as a preload meal suggests that protein has a suppressive effect on satiety and might be a useful tool in order to cause weight loss. The weight loss effects of high protein diets that include red meat and eggs, suggest that these foods are important dietary component that prevent obesity related diseases such as diabetes and cardiovascular disease.
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