There's a super-nutrient that boosts your workout results, fat-burning power, mood, and motivation. It's fiber—and you probably haven't been getting enough. Until now.
Fiber's fuddy-duddy image is getting a makeover, and a well-deserved one. For starters, new research shows fiber is critical for active women, helping you work out harder and longer.
A type of carbohydrate, fiber helps food pass through your system. Which is where its potency lies: "Fiber slows down the digestion and absorption of food, so you get steady energy that lasts," says Sarah Romotsky, R.D.N., of the International Food Information Council Foundation. One way it may ensure that stamina is by boosting the population of a type of gut bacteria that improves the way your body handles sugar, research published in the journal Cell Metabolism shows. (Not to mention, one benefit of a high-fiber diet might decrease your risk of breast cancer.)
A better workout isn't the only benefit from the rough stuff. Check out the three other important benefits of fiber for staying healthy, slim, and strong.
Torch more fat and calories.
Fiber revs your metabolism. (That's why it's one of the most important nutrients for weight loss.) Women who substitute high-fiber grains for refined ones have a higher resting metabolic rate, which means they burn more calories throughout the day, according to research published in the American Journal of Clinical Nutrition. This effect is probably due to the increased energy your body has when it gets enough fiber, along with a steady blood sugar level, says study author Susan B. Roberts, a senior scientist at the USDA Human Nutrition Research Center on Aging at Tufts University and the founder of the iDiet weight-loss program.
Fiber is especially beneficial for keeping your weight healthy because it produces short-chain fatty acids when it's broken down by your gut bacteria, says Wendy Dahl, Ph.D., an associate professor in food science and human nutrition at the University of Florida. These fatty acids help induce feelings of fullness and keep your appetite in check.
One kind of fiber called resistant starch may actually increase your body's ability to burn fat, including belly fat, says Michael Keenan, Ph.D., a food science professor at Louisiana State University. It does this by triggering a mechanism that prompts your body to use fat instead of carbs for fuel. Eaten daily, foods with this starch—like beans, legumes, and whole grains, as well as cooked and cooled potatoes, pasta, and rice (the cooling process makes them develop resistant starch)—can have a big impact. (Try these Healthy, High-Fiber Lentil Recipes That Won't Weigh You Down.)
Keep your body balanced.
If you're packing in a lot of postworkout protein to help build and maintain muscle, fiber can be an important counterbalance, Dahl says. Here's why: Consume too much protein, and some of it may not be digested and will instead be broken down by gut bacteria, which creates inflammation-causing compounds, she explains.
But when you eat enough fiber, the nutrient acts as a deterrent. The bacteria break it down instead, which prevents this harmful process. For the best results, make sure that at least some of your daily protein comes from plant sources, like beans and peas, that contain plenty of fiber, Dahl says. (These vegetarian dinners are high in protein and fiber.)
Fiber boosts the population of good gut bugs in your digestive tract, which research has linked to a bolstered immune system and even a better mood, Dahl says. (Really—gut health and happiness go hand in hand.) Your bones benefit too. Certain types of fiber, like chicory root, make it easier for your body to absorb magnesium and calcium, which are both critical for a strong frame. A fiber-rich diet can even help ward off knee problems. In a study at Boston University School of Medicine, people who ate the most fiber were less likely than people who consumed less fiber to experience worsening knee pain or develop painful osteoarthritis in their knees later, probably thanks to fiber's anti-inflammatory benefits, the researchers say.
But how much fiber do you actually need?
To reap the benefits of fiber, aim for at least 25 grams of fiber every day—most of us get only about 16 grams. Eat a variety of fruits, vegetables, whole grains, beans, and nuts, and you'll end up with the right mix of different types of fiber, Romotsky says. (Try these recipes using high-fiber foods.) And as you up your fiber intake, drink more water to prevent stomach upset, she says. Your new goal: nine glasses of H2O a day.
Some packaged foods contain "functional fiber," like psyllium and inulin. While it's OK to eat this type to help fill the gaps, eating whole foods gives you the benefit of fiber plus other nutrients as well. (And, in case you were wondering, this is what you need to know about having too much fiber in your diet.)