FEED YOUR BACTERIA:

Our bodies don't have the capacity to break down fiber. So it moves through our small intestines largely unchanged, and eventually - approximately 4 to 10 hours after a meal - reaches our colons.

Here, inside the large intestine, the fiber meets a whole crew of microbes that can digest the fiber. Bacteria in your large intestine can break down certain dietary fibers into smaller molecules. And these smaller molecules can trigger the release of not only GLP-1, but also another key hormone that decreases your appetite, called PYY (peptide YY). These smaller molecules also can suppress appetite on their own, and have been linked to lower body weight and better glucose regulation.

Since this extra boost of GLP-1 and PYY occurs hours after you eat, it can tamp down cravings between meals and even the overall desire to eat the next meal. "PPY regulates satiety - that is how long you wait between meals," says the University of Arizona's Frank Duca. "The release of PYY, in addition to the GLP-1, can increase the length of time between meals," he says.

These hormones may even influence how much you eat at the next meal. "This is what's called a second meal effect," says Edward Deehan, a nutritional microbiologist at the University of Nebraska-Lincoln. "If you eat a lot of fiber at one meal, by the time it's in your colon, it's around the time of your next meal. So you may have improved insulin responses and improved satiety or a feeling of fullness," Deehan says.

But, not all fiber is equal: To get this extra boost of satiation hormones, you need to eat fiber that bacteria can digest. These fibers are called fermentable because bacteria literally ferment them, in a similar way that yeast ferments barley into beer.

Scientists, such as Duca, have just started trying to figure out which fermentable fibers may be best at suppressing appetite and inducing weight-loss. "So the agricultural community in the U.S. could prioritize the growing of grains with these fibers," he explains.

In one preliminary study with mice, Duca and his colleagues found that a fiber in barley, called beta-glucan, induced the most weight loss in obese animals. "At face value and, at least in our settings, it was only beta-glucan that was effective," he says.

How To Add Barley To Your Diet

Cooking barley is super easy. Some recipes call for soaking the grain before boiling. But it's not necessary. Simply add one cup of barley and three cups of water to a pot.

For pearled barley, continue boiling for about 30 minutes. For hulled barley, boil for about 40 minutes. Strain the water and you're ready!

You can throw barley into soups or on salads and boiled barley is a great fiber-rich substitute for white rice. You can also buy barley flour and use it for baking breads, muffins and pancakes.

Beta-glucan is also found in oats and rye. And indeed, studies with people have found that beta-glucan fiber may improve insulin sensitivity, lower blood pressure and increase satiation between meals.

Other fermentable fibers include dextrin in wheat, oligosaccharides in beans, peas and lentils, and pectin in apples, pears and green bananas.

If your diet currently doesn't include much fiber, Duca says, don't worry too much about which fiber you start adding. "Just being aware of how much fiber you're eating and increasing it, that's a huge step to improving your health," he says. "Then once you get into the habit of eating more fiber, you can be more specific about adding more beta glucan and barley."

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