Last updated: Oct 07, 2014
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Consider this: Right now, as you're sitting there, there's a battle raging in your belly. Some 1,000 species of bacteria are duking it out, trying to establish dominance. Why should you care? Because whether the good bacteria in your gut or the bad triumph doesn't just decide how well you digest your dinner, respond to allergens and fend off diseases—it also helps determine how much weight you're likely to gain. Or lose.



"Simply put, if you get the microbiome—that collection of bacteria inside you—healthy, you will lose weight," says Raphael Kellman, MD, a New York City physician and author of The Microbiome Diet. "It's less about eating a certain percentage of carbohydrates, protein and fat than about correcting the overgrowth of unhealthy bacteria, which is making you crave the wrong foods, triggering inflammation."

A flurry of ground-breaking findings are helping to connect the dots about how our gut bacteria may shape our, well, shape. In a study in the British Journal of Nutrition, obese women who took a probiotic supplement (of the bacteria Lactobacillus rhamnosus) lost twice as much weight and fat over about six months—and were better at keeping it off—as those who took a placebo. Probiotics may have helped by controlling the women's appetites, which seem to have waned as their microbiomes changed.

Unhealthy gut bacteria also produce food cravings: A study published in BioEssays suggests that some microbes may drive us to eat doughnuts or another tempting treat. These gut bugs send chemical messages to the brain that sway our appetite and mood—perhaps making us feel anxious until we gobble a square of dark chocolate or a T-bone steak.

Fortunately, we can begin to take control by feeding our microbiome the right foods. "I tell my patients, 'The bacteria follow the food,'" says gastroenterologist Robynne Chutkan, MD, founder of the Digestive Center for Women in Chevy Chase, Md., and author of Gutbliss. "What we eat dictates the kind of bacteria we grow in our gut garden."

This is big news: There are trillions of microbes in your belly that will—if you feed them well—help you fight flab and win.

Gut check #1: Get Your Two P's
Basically, it all begins with probiotics and prebiotics, components of food believed to play an important role in improving gut health. Probiotics are a type of good bacteria, similar to the ones that already reside in your gut. Ingesting these organisms aids digestion and helps change and repopulate intestinal bacteria to balance what doctors refer to as "gut flora." Prebiotics are plant-fiber compounds, also found in food, that pass undigested through the upper part of the gastrointestinal tract and help stimulate the growth of good bacteria. When pre- and probiotics are combined, they become an intestinal power couple (or, in blunter terms, they kick nutritional butt).

RELATED: 4 Surprising Health Benefits of Yogurt

Gut check #2: Go Live
Fermented foods deliver probiotics directly to the gut. A cup of yogurt a day? It's a nice start. Look for products that say "live and active cultures" on the label, and be careful when it comes to fruit-infused flavors: Some are loaded with sugar, which can feed bad bugs, so be sure to check the ingredients and aim for fewer than 15 grams per serving. For even more probiotics, try Greek yogurt or kefir, a tangy dairy drink that's packed with good bugs. A 2011 Harvard study found that yogurt was more strongly linked to weight loss than any other health food. In fact, people who ate an extra serving a day lost nearly a pound every four years.

 
 


Gut check #3: Down Some Fiber
It does more than fill you up: Research shows that foods that are high in fiber help promote the growth of friendly bacteria. Case in point: In a University of Illinois study, people who ate high-fiber snack bars experienced a growth of anti-inflammatory bacteria in their bellies.

RELATED: 20 Best Foods for Fiber

Gut check #4: Mix Up Your Menu
Eat an assortment of foods to encourage a more varied metropolis in your belly. Recent studies suggest that the intestines of lean people look more like bustling cities than sleepy towns. (Translation: They're densely populated and diverse.) One study showed that individuals who had a healthy weight, body mass index, waist circumference and blood sugar level were more apt to have high levels of three different types of bacteria—Firmicutes, Bifidobacteria and Clostridium leptum. What's more, in a pair of French studies, people with diverse gut microbiomes were less likely to be obese or at risk of diabetes. Plus, their intestinal ecosystems were home to fewer pro-inflammatory bacteria. It's easy to change up your meals: If you had salad with grilled chicken yesterday, for example, go with a fish taco or a tofu stir-fry today.

Gut check #5: Skip Bad-News Foods
What you don't eat is every bit as crucial as what you do add to your diet. Keep your gut flora fit by cutting back on these offenders.

Refined carbs
Fatty and sugary foods not only tend to lack fiber—which is ideal food for the microbiome—but can also cause bad bacteria to thrive. And let's face it: If you're pounding that bag of potato chips, chances are you're not munching on celery sticks, blueberries and other gut-friendly eats.

Animal protein
A diet heavy in fat and protein (such as meat and cheese) feeds a type of bacteria, Bilophilia, that has been linked to inflammation. Lawrence David, PhD, assistant professor at Duke University's Institute for Genome Sciences and Policy, saw the levels of this bacteria shoot up in study participants scarfing ribs and brisket, but not in those eating squash and lentils. Dr. Kellman suggests limiting red meat to once a week. It's smart for your heart—and hips!