More Protein Means Less Hunger

Researchers have discovered that eating a higher-protein diet boosts the level of a hunger-fighting hormone produced by the body, according to a report in the September issue of Cell Metabolism. ("Critical role for peptide YY in protein-mediated satiation and body-weight regulation," Cell Metabolism vol. 4, 223233) The same researchers had found earlier that the hormone, peptide YY (PYY), given by injection, could reduce food intake by one third in normal-weight and obese people.

"We've now found that increasing the protein content of the diet augments the body's own PYY, helping to reduce hunger and aid weight loss," says Medical Research Council clinician scientist Rachel Batterham of University College London, who led the study.

Research shows that dietary protein enhances satiety and promotes weight loss, but science has not discovered the actual mechanisms that affect appetite. The researchers previously showed that meals with higher protein levels stimulate greater release of PYY than either high-fat or high-carbohydrate meals and produce a greater reduction of hunger. This study looked at genetically modified mice that could not produce PYY. They ate more and became obese, and also were resistant to the beneficial effects of a high-protein diet, demonstrating a direct connection between protein and PYY. After treatment with PYY, the mice lost weight.

"The findings show that PYY deficiency can cause obesity, and that PYY appears to mediate the beneficial effects of increased-protein-content diets," Batterham says. "One potential weight-loss strategy is therefore to increase the satiating power of the diet and promote weight loss through the addition of dietary protein--harnessing our own satiety system.

"Such a diet is perhaps more typical to that of our hunter-gatherer ancestors," Batterham points out. Currently, the average Western diet gets 49% of energy intake from carbohydrate, 35% from fat, and 16% from protein, while our ancestors obtained 19% to 35% of energy from protein, 28% to 47% from fat, and 22% to 40% from carbohydrate. This suggests that reduced protein intake may be partly responsible for the Western world's high levels of obesity and diseases of affluence.

Batterham expressed the need for large, long-term clinical trials before any particular diet could be recommended. She also observed that an effective diet would not resemble the Atkins diet, with its high saturated-fat content.