Think your weight is just a matter of calories in versus calories burned? Think again. Scientists are learning there are other factors at play—trillions of them. Recent research shows the large colony of bacteria that live in your gut, called your microbiome, may do much more than help you digest food. In fact, your microbiome may affect your brain, heart, metabolism, weight, and risk for diseases like cancer and diabetes.
You probably don’t think much about your microbiome, but it’s a significant part of who you are. You have about the same number of bacteria in your gut as you do human cells in the entire rest of your body. How exactly does your microbiome affect your health and weight? Here are some noteworthy points:
Diet can throw off your bacteria balance: A few studies have shown that eating a Western diet—one high in fat and refined carbs and low in fiber—can disrupt the bacteria in your gut and cause you to gain weight. The high rates of caesarean births and low rates of breastfeeding in this country contribute to less diverse gut bacteria as well . In one study done at Johns Hopkins University, when researchers transplanted the gut bacteria of obese mice into the guts of thin mice, the thin mice gained weight.
Another study done at the University of Pennsylvania showed that just 24 hours of a diet low in fiber and high in sugar and fat caused the gut microbiome to switch to a pro-inflammatory state. Research has also shown inflammation in the gut can cause harmful toxins to leak out and enter the bloodstream, increasing risk for metabolic problems, such as metabolic syndrome and diabetes, and weight gain. 
Antibiotics can interfere: A few studies have shown that over prescribing antibiotics to children may make them more prone to obesity later in life. A 2012 study published in the journal Nature found that mice that consumed low-dose antibiotics gained weight despite eating the same number of calories as the control mice, which stayed thin.
Unbalanced microbiomes breed trouble: In a European study, researchers looked at the bacteria of stools from about 300 Danish volunteers, both obese and lean. They found the participants with less diverse microbiomes had higher levels of inflammation, greater insulin resistance, and other risk factors for metabolic diseases. The obese subjects with low diversity also gained significantly more weight over the course of nine years than the subjects whose microbiomes were more diverse.
So now that you know how your microbiome affects your metabolism, what can you do about it? Here are some tips:
Be proactive with prebiotics: Foods known as prebiotics work to repopulate the positive bacteria in your microbiome. They include asparagus, artichokes, bananas, garlic, leeks, onions, beans, and other high-fiber foods. Fermented foods that contain live bacteria, such as yogurt, kefir, sauerkraut, and kimchi are also beneficial to the microbiome. Try to incorporate more of these foods into your diet to populate the good guys in your gut.
Eat fewer inflammatory foods: Inflammatory foods include refined carbohydrates such as white bread and pasta; red meat, processed meats (hot dogs, sausage); fried foods; soda and other sweetened beverages; margarine, shortening, and lard; and other foods low in fiber and high in sugar and/or fat. (You know these foods are bad for your waistline anyway). Instead, opt for anti-inflammatory foods such as fresh fruits such as strawberries, cherries, oranges, and blueberries; olive oil; green, leafy vegetables such as spinach and kale; tomatoes; nuts, such as almonds and walnuts; whole grains; and fatty fish like tuna, salmon, mackerel, and sardines.
Hold the antibiotics: In addition to prescription medication, research shows you can also get antibiotics from meat and poultry that have been treated with the drugs. To avoid ingesting antibiotics in foods, check the labels of all meat, eggs, poultry and dairy you buy. Just because a food claims to be “organic” doesn’t mean it will truly pass the test. Look for the certified USDA Organic label, which ensures the product comes from animals that have never been treated with bacteria killing drugs.
Keep up with your Curves workouts: A 2017 study found exercise training helped foster healthy gut bacteria, independently from diet. The results suggest that the combination of regular exercise and a healthy body weight can support healthy gut bacteria and therefore, better weight control. Eating lower calorie/high nutrition foods and engaging in a regular exercise routine like the Curves’ Circuit will help keep you energetic and trim.