How dietary fiber increases fullness and delays hunger.
What the evidence says
- Fiber is positively correlated with satiety — higher fiber foods are more filling per calorie[1],[2]
- Fiber slows gastric emptying — but the effect is on the return of hunger, not on satiety: the same trial measured satiety and fullness hourly and found no difference between the high- and low-fibre meals[3]
- Removing fiber from food accelerates gastric emptying (186 min vs 232 min)[3]
- Hunger returns more rapidly after low-fiber meals[3]
- Fiber also blunts glycemic response — blood glucose AUC 29% lower with high-fiber meal (160 vs 226 mmol/min/dl, P < 0.05)[3]
- Fiber promotes satiation and alters secretion of gut hormones — specifically, soluble fiber fermentation produces GLP-1 and PYY, hormones that induce satiety[2],[4]
- Average US adult fiber intake is less than half recommended levels; popular low-carbohydrate diets are particularly low in fiber[2]
- Paleolithic fiber intake estimated at ~46 g/day (from fruits and vegetables, not grain), versus ~20 g in the current American diet — modern intake has declined to less than half ancestral levels[5]