A study published in the Journal of Nutrition found that fiber supplements derived from legumes may help improve appetite, reduce food intake, and lower inflammation in adults who are overweight. For the study, researchers divided 88 overweight adults into groups receiving 6, 12, or 18 grams of fiber, or a placebo, for 14 days. The legume fiber was a prebiotic—a type of fiber that can be fermented by probiotic bacteria in the gut. Researchers measured the participants’ appetite levels, food intake (in the form of a test meal and a 24 hour dietary recall), and inflammatory markers immediately before and after the 14-day treatment period on day zero and on day fifteen. Here's what they found:

• The fiber groups experienced a statistically significant decrease in appetite, food intake, and inflammatory markers.
• The relationship between the fiber supplement and these outcomes was generally dose-dependent, meaning more fiber led to more positive results.
• The fiber stimulated a statistically significant growth of bifidobacteria—a type of probiotic—as compared with the control group.

The researchers speculated that the positive changes observed in the fiber groups were largely due to a change in the functioning of gut bacteria. The findings are consistent with another study that came to a very similar conclusion, namely that prebiotic fiber can help increase bifidobacteria and reduce inflammation in children who are overweight. Nevertheless, it should be noted that the study’s lead author declared a potential conflict of interest—they're employed by a company that extracts food fiber from vegetables.

Source: Journal of Nutrition