Epidemiological studies have shown that dietary fiber consumption is inversely
associated with body weight, and some research suggests that foods high in fiber increase
satiety and reduce energy intake. The mechanism for this relationship is unknown, but
may be related to changes in glucose, insulin, or gut hormone concentrations. Fiber may
also benefit health by improving laxation, altering the gut microbiota, and increasing
production of short chain fatty acids (SCFA). The following work describes two review
articles, as well as an intervention study designed to help examine these effects.
The first review focuses on the benefits of dietary fiber in clinical nutrition. This
allowed for evaluation of the physiological effects of different types and combinations of
fiber in subjects on a controlled diet. In general, blends of fibers with varying
physicochemical properties provided greater benefits and were better tolerated than single
Next, a systematic review of the effects of fiber intake on gut hormone
concentrations examined the evidence for this relationship. Considerable variation was
found in study design, population, fiber type and dose, which made comparisons difficult.
Few studies reported a significant effect of fiber on gut hormone levels, and data suggest
caloric load may have a more significant influence.
Lastly, a randomized, double-blind, crossover study examined the effects of three
novel fibers with varying physicochemical properties on satiety, stool characteristics, and
the role of gut hormones, glucose, and insulin in appetite regulation. On Day 1 of the
study, healthy men and women consumed either a low-fiber control breakfast or 1 of 4
breakfasts containing 25 g fiber from soluble corn fiber (SCF) or resistant starch (RS),
alone or in combination with pullulan (SCF+P and RS+P). Subjects rated satiety using
visual analog scales (VAS), and blood samples were collected at various time points for 3
hours following breakfast. The fiber treatments did not influence satiety or energy intake
compared to control. The RS+P treatment significantly reduced glucose, insulin, and
To examine the effects of chronic fiber intake, subjects consumed the fiber
treatments at home for 6 additional days, with a 3 week washout between periods. Stool
samples were collected on Day 7 and tolerance was assessed following fiber intake on
Day 1 and Day 6. Fiber did not alter stool weight or stool consistency. SCF reduced pH
and increased total SCFA production compared to control, while RS+P increased the
percentage of butyrate. Overall, fiber was well tolerated, although treatments containing
pullulan tended to cause minor increases in symptoms. Both SCF treatments resulted in a
significant shift in the microbial community.
Results from these studies confirm that different fibers vary in their physiological
effects, and consuming fiber from a variety of sources may be most beneficial. Although
increased satiety and improved bowel function are commonly reported benefits of fiber
intake, it is clear that not all fibers exert these effects. In addition, the relationship
between fiber and potential biomarkers of satiety remains unclear. Thus, it is important
to evaluate the effects of different fibers in human studies to better guide
recommendations for their use.