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6 Sep, (foodconsumer.org) – The presence of a peptide hormone in the gut accounts for the feeling of fullness experienced by people after consuming a protein-rich meal, scientists have found. The hormone known as PYY sends signals to the brain and reduces feelings of hunger, researchers said.
Researchers had earlier found that increased levels of the hormone reduce intake of food by about a third in both normal weight as well as obese individuals when given by injection. It is well known that a protein-rich meal induces the feeling of fullness, but the exact mechanism through which this occurred was not clear. Researchers hope the new findings would offer a new tool to fight obesity.
Rachel L. Batterham, M.D., of University College London, and colleagues found that increasing the protein content in meals increased the level of PYY in the body and dispelled hunger quickly. "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," Batterham said in a press release.
In a study of both normal weight and obese people, researchers were able to show that high protein content in meals stimulated greater release of PYY than either high-fat or high-carbohydrate meals and result in a greater reduction of hunger.
To further investigate these findings the researchers conducted a study in mice. High protein intake by these lab mice reduced the calories consumed by them, the researchers found. Mice on such diets produced higher levels of PYY and remained lean.
Additionally researchers found that genetically modified mice in whom the ability to produce PYY was hampered ate more food and put on more weight.
This finding may help explain how Atkins diet, which abandons carbohydrates in favour of protein and saturated fat works in reducing weight. "People on the Atkins diet don't feel as hungry — that's how it work," Batterham said in the study published in the journal Cell Metabolism.
In a paper published in 2002 in the journal Nature, Batterham's team already demonstrated that the hormone PYY reduces appetite in humans. The new study was undertaken to establish exactly what link exists between the two, she explained.
"The findings show that PYY deficiency can cause obesity and that PYY appears to mediate the beneficial effects of increased-protein content diets," Batterham said. "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."
Researchers also said the so-called "caveman" diets, which included 35 percent more protein, may explain why our ancestors were able to maintain near-perfect weight.
In contrast, the average Western diet derives 49% of energy intake from carbohydrate, 35% from fat, and 16% from protein. This may explain why some people are constantly hungry, Batterham said.
"We now need to do a big study in obese patients and see whether these short-term effects translate into longer-term benefits," she added. "People are just beginning to realize how much obesity is going to cost us."
However, eating a diet with moderately high protein may not necessarily be effective against becoming overweight and obese, according to T. Colin Campbell, professor in nutrition at Cornel University. On the contrary, he found in a large epidemiological study that a diet with high protein along with high fat may exactly the cause for the obesity epidemic in the West.
Dr Campbell pointed out in his popular book titled "China Study" that the Chinese in rural areas who eat more calories, but much less protein and fat than Americans are lean, suggesting that people need to increase carbohydrates and reduce protein and fat in their diet in order to avoid weight gain or to lose weight.
Dr. Batterham cautioned that it was too early to start off consuming large amounts of proteins. Some large, long-term studies are needed before any specific diet is recommended, she concluded.
"It's not a diet that you would go on for a few months. You would go on it for life. We need to check that it would be compatible with lifestyle and look at the safety aspect."
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