Effects of fiber on satiety, food intake, glucose, insulin, and gut hormones in healthy human subjects

Epidemiologic studies suggest that people who eat more fiber have a lower body weight than people who eat less fiber. Potential mechanisms for this relationship may include greater feelings of satiety, reductions in food intake, or changes in blood glucose, insulin, or gut hormone levels. The following work describes two unique intervention studies designed to help explain this relationship.;In the first study we hypothesized that certain types of fiber would enhance satiety more than others when consumed in muffins for breakfast. Healthy men and women participated in this randomized double-blind, crossover study comparing satiety after subjects consumed four different fibers and a low-fiber control. Subjects used 100 mm visual analog scales (VAS) to rate satiety for 3 hours after muffin consumption. Satiety differed among treatments. Resistant starch and corn bran had the most impact on satiety, while polydextrose had little effect and behaved like the low-fiber treatment.;In the second study we hypothesized that increasing doses of fiber would increase satiety and decrease food intake in a dose-dependent manner. We also hypothesized that glucose, insulin, ghrelin, GLP-1, and PYY 3-36 would change in proportion to fiber dose. Healthy men and women participated in this randomized double-blind, crossover study. Subjects consumed muffins with 0, 4, 8, and 12 g of mixed fibers and proceeded to rate satiety with VAS over a three-hour period. Blood was drawn at regular intervals and ad libitum food intake was assessed at two different time points. The 12 g fiber muffin was consistently and significantly more satiating than the 0 g muffin; however, food intake did not differ among treatments. Glucose, insulin, ghrelin, and GLP-1 differed among treatment doses, but not in the manner we expected. Glucose and insulin did not correlate with each other or with appetite. Ghrelin was significantly higher after 12 g of fiber than after all other doses, and GLP-1 decreased consistently with fiber dose. PYY 3-36 did not differ among treatments.;Results from these studies indicate that certain types and doses of fiber positively influence satiety. However, caution should be used when making blanket statements about fiber as a generic substance; this research suggests that some types and doses are not as effective as others. Furthermore, feelings of satiety may not be consistently linked to food intake or other commonly accepted physiologic measures for satiety.