Satiety Hormones

The body uses a complex system of hormonal and neural signals to regulate appetite and food intake. Understanding these satiety mechanisms provides insight into one of the most researched aspects of nutrition science.

Leptin: The Satiety Hormone

Leptin is a hormone produced by fat cells that plays a key role in energy balance regulation. It signals to the brain about the body's energy stores and helps regulate long-term energy balance. When leptin levels are adequate, the brain receives signals of satiety and fullness. When energy stores are depleted, leptin levels decrease, signalling hunger.

Ghrelin: The Hunger Hormone

Ghrelin is produced primarily in the stomach and signals hunger to the brain. It increases before eating and decreases after food consumption. Ghrelin levels are influenced by meal timing, sleep quality, and energy balance status.

Peptide YY (PYY) and GLP-1

These hormones are produced in the intestines in response to food consumption, particularly in response to proteins and fats. They signal satiety and slow gastric emptying, contributing to feelings of fullness.

Cholecystokinin (CCK)

CCK is released in response to dietary fats and proteins entering the small intestine. It contributes to short-term satiety signals and helps regulate the rate at which food moves through the digestive system.

Mechanical Satiety Signals

Beyond hormones, mechanical signals from the digestive tract contribute to satiety. Stomach distension—physical fullness—provides feedback to the brain about food consumption. This is why foods with higher volume can influence satiety independently of their caloric content.

Nutrient-Specific Effects on Satiety

Protein: Research consistently shows that protein produces strong satiety signals. This is due to both hormonal responses and the thermic effect of protein digestion.

Fiber: Dietary fibre increases food volume, slows digestion, and produces satiety signals. Foods high in fibre tend to produce greater feelings of fullness.

Fats: While calorie-dense, fats trigger satiety hormones and can contribute to feelings of fullness when consumed with adequate protein and fibre.

Refined Carbohydrates: Low-fibre carbohydrates may produce weaker satiety signals and faster glucose absorption, leading to quicker hunger return in some individuals.

Individual Variation

It's important to recognise that satiety responses vary significantly between individuals. Factors including genetics, gut bacteria composition, sleep quality, stress levels, and previous eating patterns all influence how satiety signals are generated and perceived.

Practical Implications

Understanding satiety mechanisms explains why different foods produce different feelings of fullness and why eating patterns vary between individuals. However, these are general observations about physiological mechanisms, not prescriptions for individual dietary choices.