Scientists discover how high-fiber foods make people feel fuller

In a study published in The science of translational medicineresearchers at Imperial have found that a high-fibre diet stimulates the release of a key appetite-suppressing hormone, in the ileum, part of the small intestine.

Peptide tyrosine tyrosine (PYY), which is known to reduce appetite and food intake, was released in greater amounts from ileal cells when people ate a high-fiber diet.

The ileum, the longest part of the small intestine, plays an important role in regulating appetite by secreting enzymes and hormones, but little has been known about how it interacts with different types of food until now.

The researchers also identified several key metabolites – small molecules resulting from the breakdown of food – that caused the release of PYY, leading to the intriguing possibility that in the future foods could be designed to curb hunger.

In the study, a small group of healthy volunteers were asked to consume a variety of meals, including fiber-rich and fiber-rich foods such as apples, chickpeas, carrots, sweets and white bread, over four days. They were fitted with nasoendoscopic tubes – flexible tubes that went down into their small intestines. This allowed the researchers to take samples of ‘chyme’ – the substance produced in the ileum – before and after the participants ate meals.

Along with finding that the environment inside the ileum was much more responsive to fasting and feeding than previously thought, the research team found that foods higher in fiber changed the microbiome and stimulated the release of PYY from ileal cells more than the lower fiber. foods did.

This was true even when high-fiber foods were broken down structurally—for example, mashed chickpeas or apple juice.

Molecules such as stachyose and the amino acids tyrosine, phenylalanine, aspartate and asparagine, commonly found in foods such as beans, cheese, meat and poultry, were all found to promote the release of PYY.

Dr. Aygul Dagbasi from Imperial’s School of Metabolism, Digestion and Reproduction and lead author of the study said: “We now understand how dietary fiber is associated with lower hunger, compared to a low-fiber diet, and that certain fibers and amino acids stimulate PYY. For example, oats and legumes have high amounts of fiber and they are a good source of protein, so are good foods to promote satiety.”

Designing a healthier diet

The places deep in the human digestive tract are difficult to access, so this study represents a step forward in scientists’ understanding of the role of the ileum.

Imperial’s Professor Gary Frost, who led the study, explains: “Our research not only provided more detailed information on how the ileum changes continuously in response to fasting and feeding, but also has implications for the design of healthier diets. If we can find ways to deliver certain foods to the right part of the gut, which could help people struggling with their weight, give them more control over their appetite and help them stick to a diet.”