Dietary fibre consists of indigestible carbohydrates and lignin found in plant-based foods. Unlike digestible carbohydrates, fibre is not broken down by human digestive enzymes and therefore contributes minimal calories to dietary intake. However, the metabolic and physiological effects of fibre extend far beyond its caloric contribution.
Dietary fibre is classified into two primary categories based on water solubility:
Soluble Fibre: Dissolves in water to form a viscous gel within the digestive tract. Soluble fibre slows gastric emptying, promotes satiety, and moderates blood glucose responses. It also serves as substrate for beneficial gut bacteria, producing short-chain fatty acids that nourish colonic epithelium. Sources include oats, barley, legumes, apples, and citrus fruits.
Insoluble Fibre: Does not dissolve in water and adds bulk to stool, promoting regular bowel movements and maintaining colonic health. Insoluble fibre has limited direct effects on blood glucose or lipid metabolism but supports digestive regularity. Sources include whole wheat, bran, vegetables, and many fruits.
Adequate fibre intake is associated with improved long-term metabolic outcomes. Prospective cohort studies demonstrate that individuals consuming higher fibre intake maintain lower body weights, exhibit better glucose tolerance, and show improved lipid profiles compared to those consuming lower fibre amounts. The mechanisms include satiety effects, moderated glucose responses, and alterations in gut microbiota composition that influence energy harvesting from food.
The relationship between fibre intake and body weight management operates through multiple mechanisms. Soluble fibre increases meal volume without substantial caloric contribution, promoting satiety and reducing overall energy intake. Fibre-rich foods typically require more chewing and slower consumption, allowing satiety signals to develop before excessive intake occurs. Additionally, fibre influences gut microbiota composition; high-fibre diets promote growth of bacteria that produce butyrate and propionate, metabolites with appetite-suppressing effects.
Excellent sources of dietary fibre include:
General guidelines recommend 25-35 grams of dietary fibre daily for adults. However, most populations in developed nations consume substantially less. Increasing fibre intake should be gradual to allow digestive adaptation and minimize gastrointestinal discomfort. Adequate hydration supports optimal fibre function.
Last Updated: March 2026
