Meaning of Peptide YY

What is Peptide YY?

PYY is a peptide consisting of 36 amino acids, primarily secreted from the enteroendocrine L-cells of the ileum and colon. Blood concentrations rise after meals, signaling the digestive tract and the brain that nutrients have entered.

While the nickname 'satiety hormone' explains some of its functions, it does not mean that PYY is a single switch for appetite.

When is it secreted?

Levels are relatively low during fasting and increase after meals. The response may vary depending on the energy intake, the composition of proteins, fats, and carbohydrates, the speed at which food passes through the intestines, and the individual's condition.

Levels can remain high for several hours after a meal, but time-based patterns and measurement methods differ by study. A single value at one point in time does not represent the daily secretion.

What are PYY1-36 and PYY3-36?

The initially secreted PYY1-36 can be converted into PYY3-36 by the DPP-4 enzyme. Because the two forms have different affinities for neuropeptide Y family receptors, it is difficult to group their physiological actions as one.

In human blood after a meal, PYY3-36 is often described as the primary form. It is important to check whether a study measured total PYY or a specific form.

How does it affect appetite?

PYY3-36 can act to suppress food intake by involving gut-brain signaling via Y2 receptors and hypothalamic circuits. It may also influence gastrointestinal motility and the movement of food.

The actual termination of a meal is determined by a combination of gastric distension, CCK,GLP-1, taste, reward circuits, and the social environment. It cannot be explained by PYY alone.

How is it different from GLP-1?

Both hormones can be secreted from the L-cells of the intestine after a meal and are involved in satiety signals. However, PYY acts through the NPY receptor family, while GLP-1 acts through the GLP-1 receptor, insulinand glucagonand the way they affect the body is also different.

The fact that they originate from the same cell does not mean they are the same hormone or the same treatment. A distinction is also made between medication and natural secretion.

Is it the opposite of ghrelin?

GhrelinGhrelin tends to increase before fasting and is related to the motivation to eat, then decreases after a meal, so it is often introduced as being in the opposite direction of PYY. However, these two signals do not interlock exactly like a simple seesaw.

Sleep, stress, sensory stimulation, and learned eating habits overlap with hormonal signals. Hunger is not predicted by a single value.

Can PYY be increased through food?

Proteins, fats, and carbohydrates can all stimulate PYY secretion, and the magnitude of the response varies by research conditions. A ranking of 'foods that increase PYY the most' does not directly predict an individual's long-term satiety and weight change.

Practically, proteins, dietary fiberand meals with sufficient food volume should be eaten slowly, and the actual duration of satiety should be recorded.

When is a PYY test performed?

PYY measurement is mainly used in research and specific endocrine or gastrointestinal evaluations. It is not a routine standard test for diagnosing general appetite issues or obesity.

Values may vary depending on specimen processing, analysis methods, and whether it is measured during fasting or after a meal. Commercial test numbers are not used as independent treatment goals.

How is it interpreted in weight management?

Intestinal hormone responses may change after weight loss or bariatric surgery, but results cannot be explained by PYY changes alone. Food intake, absorption, GLP-1, and neural signals change together.

Specific supplements or extreme diets are not chosen simply because they stimulate PYY. A sustainable eating structure and overall energy balanceis prioritized.

Common Misconceptions and Safety Standards

The postprandial rise of natural PYY and research results from administering high-dose peptides externally are not the same exposure. The reduction in intake seen in experimental injections is not directly translated to the effects of general food.

Persistent early satiety, vomiting, unexplained weight loss, or severe abdominal pain should not be self-diagnosed as a 'high satiety hormone state'; instead, seek an evaluation for gastrointestinal or systemic causes.

What should be recorded in an appetite log?

Record hunger before a meal, the comfortable satiety at the time of stopping the meal, and the time when the next hunger begins using the same scale. Briefly noting the protein, fiber, volume, and eating speed of the food allows you to see recurring patterns without measuring hormones.

When postprandial satiety is short, it is not concluded that PYY is low. First, review lack of sleep, liquid diets, fast eating, and emotional triggers, and check if this repeats over several days.

If I don't feel full, does it mean I have a PYY deficiency?

The feeling of getting hungry quickly alone cannot determine the amount of PYY secretion. Appetite is shaped by a combination of meal volume and composition, stomach distension, other intestinal signals such as GLP-1 and CCK, sleep, stress, and the reward value of the food. Even for the same person, the response can differ between a liquid meal and a meal chewed slowly, or between a day with sufficient sleep and a day with a lack of sleep.

There are no routine diagnostic criteria to categorize PYY as either normal or deficient. If satiety issues recur, rather than seeking hormone tests first, record your hunger before meals, actual intake, eating speed, and the timing of the next hunger pang for 1 to 2 weeks. If severe early satiety, vomiting, or unintended weight loss occur together, evaluating the cause takes priority over appetite control tips.

How can I realistically understand PYY in a single meal?

Check your hunger before starting a meal, include foods containing protein and dietary fiber with enough volume to chew, and allow time to stop when you feel comfortably full. The goal is not to maximize PYY with specific foods, but to create the conditions to recognize various meal-termination signals from the gut and brain.

Whether hunger returns a few hours after a meal is not evaluated based on a single meal alone. We also consider whether there was a high level of activity, if a previous meal was skipped, and if there were beverage calories or snacks. As these records accumulate, the points for adjustment in your current eating structure become clearer than a list of 'foods that increase PYY'.

The goal of recording is not to eliminate hunger completely, but to find comfortable satiety and stability until the next meal.