A number of studies have suggested a diet high in protein can aid weight loss. Now, researchers have shed light on the underlying mechanisms of this association, which may open the door to new preventive and treatment strategies for obesity. Share on Pinterest Researchers have learned more about how protein-rich foods affect appetite and weight. In a new pilot study, researchers from Imperial College London in the United Kingdom reveal how phenylalanine – an amino acid produced by the digestion of protein – boosts levels of a hormone that tells us when we are full, leading to reduced food intake. Lead author Mariana Norton will present the findings at this week’s Society for Endocrinology annual meeting in the U.K. Previous studies have shown that a diet high in protein – essential nutrients found in foods such as milk, fish, eggs, and poultry – can help reduce body weight by suppressing appetite. According to Norton and her team, a high-protein diet can be hard to adhere to, but uncovering the mechanisms by which protein curbs hunger could lead to simpler weight-loss strategies.

How phenylalanine leads to weight loss For their study, the researchers conducted a series of experiments on rodents, which involved testing the effects of phenylalanine. Phenylalanine is an amino acid produced in the gut after consumption of foods rich in protein. Firstly, the team gave 10 mice and rats a single dose of phenylalanine and compared them with rodents that were not given the enzyme. The researchers found that mice and rats given phenylalanine showed increased levels of the hormone GLP-1, which suppresses appetite, but reduced levels of the hormone ghrelin, which increases hunger. Additionally, the researchers found that phenylalanine reduced the rodents’ food intake and increased weight loss. Rats that received the amino acid also moved around more, which the team notes may have contributed to their weight loss. Next, the team administered regular doses of phenylalanine to mice with diet-induced obesity over a 7-day period. Compared with mice that were not treated with phenylalanine, those that received the amino acid showed a reduction in weight, the researchers report.