PYY: The Forgotten Fullness Hormone

When it comes to weight loss, everyone is talking about GLP-1. Injectable drugs like Ozempic and Mounjaro, designed to mimic this natural gut hormone, have exploded in popularity because of their ability to suppress hunger.

But here’s something most people don’t realise: your body already makes GLP-1 itself. And not only that, it produces other powerful hormones that work alongside GLP-1 to control appetite.

One of the most important, and most overlooked, is Peptide YY (PYY). At Elcella, our focus is on activating the gut in a way that encourages both GLP-1 and PYY to work together, restoring the body’s own appetite-regulating system.

What is PYY?

PYY is a hormone secreted in your gut after you eat, produced by specialised enteroendocrine cells called L-cells (the same ones that release GLP-1).

Its role is simple but vital: it tells your brain, "You’re full. You can stop eating now."

Together, GLP-1 and PYY form a natural braking system for appetite. They reduce hunger, slow food intake, and help regulate blood sugar after meals.

Why isn’t anyone talking about PYY?

Unlike GLP-1, PYY has never made it into the spotlight. The reason is straightforward: pharmaceutical companies have not been able to create an effective synthetic version of it. Without a commercial incentive, PYY has stayed in the shadows, even though research shows it is just as critical as GLP-1 in appetite regulation.

The link between PYY and obesity

Here is where it gets interesting. Studies show that people with obesity release significantly less PYY after eating compared with lean individuals.

In 2006, le Roux and colleagues found that reduced PYY release was directly linked to weaker fullness signals in people with obesity. Carroll et al. (2007) later confirmed the finding, showing that higher BMI is associated with weaker PYY and GLP-1 responses.

In simple terms: when PYY levels are low, the "I'm full" signal never fully kicks in. The result is overeating, weight gain, and a cycle that is difficult to break.

Elcella switches on both PYY and GLP-1

At Elcella, we believe the future of weight management lies in supporting the body’s natural biology, not overriding it.

Our patented approach directly targets the L-cells in the lower gut, encouraging them to release not just GLP-1, but also PYY. This dual action strengthens fullness signals and makes them last longer, helping people regain natural appetite control.

The difference this makes is significant. Clinical research has shown that stimulating multiple appetite hormones produces better outcomes. For example, a study in the New England Journal of Medicine compared the dual-hormone drug (tirzepatide) with the single-hormone drug (semaglutide/Ozempic). After 12 weeks, tirzepatide patients lost more weight ( -5.4 kg vs -3.5 kg). The lesson is clear: when multiple gut hormones are activated, for example when PYY is switched on alongside GLP-1, weight management becomes more effective.

That is exactly what Elcella does - works with your biology to bring PYY back into the picture.

The bigger picture

PYY may not be a household name yet, but we are giving it the recognition it deserves and we will play our part in pioneering its importance. PYY is a key player in appetite regulation and long-term weight health.

By understanding and harnessing hormones like PYY, we can move beyond quick fixes and begin addressing the root biological drivers of obesity.

At Elcella, that is our mission: bringing PYY out of the shadows and putting it to work for lasting results.

Researched and co-written by Beatrice Chawner, MBiol BSc Biochemistry.