Fibre Types and Satiety Signalling

Evidence-informed exploration of how dietary fibre interacts with physiological hunger and fullness signals.

What is Dietary Fibre?

Dietary fibre encompasses carbohydrate compounds that resist complete digestion in the small intestine. Unlike other carbohydrates that break down into glucose, fibre passes through the digestive system largely intact, creating distinct physiological effects.

Fibre is categorised into two main types: soluble and insoluble, though most whole foods contain both in varying proportions.

Soluble Fibre

Soluble fibre dissolves in water, forming a viscous gel-like substance in the digestive tract. This characteristic slows gastric emptying—the rate at which food leaves the stomach into the small intestine. Slower gastric emptying extends the period during which nutrients are absorbed and satiety signals are generated.

Sources of soluble fibre include oats, barley, legumes, apples, and carrots. Research suggests soluble fibre's viscosity contributes to sustained fullness during and after meals.

Insoluble Fibre

Insoluble fibre does not dissolve in water. It increases stool bulk and promotes regular bowel movement. Though it doesn't form a gel, insoluble fibre still affects digestion rates and contributes to physical stomach distension—a mechanical signal contributing to satiety.

Sources include whole grains, vegetables, nuts, and seeds.

Fibre and Appetite Hormones

Satiety involves hormonal communication. The presence of nutrients and bulk in the digestive tract stimulates release of hormones including cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1), which signal fullness to the brain.

Fibre-containing foods, particularly those high in soluble fibre, tend to produce more sustained hormone signalling compared to rapidly digestible carbohydrates. This sustained signal correlates with prolonged satiety perception.

Particle Size and Food Structure

The physical structure of fibre-containing foods matters. Whole grains consumed intact produce different satiety effects than ground grain products, even when total fibre content is similar. The larger particle size of whole grains requires more chewing and takes longer to transit the digestive system.

Individual Variation

Responses to fibre vary among individuals. Gut microbiota composition, habitual fibre intake, overall diet composition, and individual digestion rates all influence how different fibre types affect satiety in any given person.

Research Context

Population studies consistently associate higher fibre intake with stable body weight, though individual responses vary. Fibre's effects on satiety appear significant but are one factor among many influencing energy intake and regulation.