That Gut Feeling: How Bacteria Can Affect Your Weight

There’s been a lot of news and hype over the past few years about the gut. Your “gut,” in case you need a reminder, is basically your digestive tract. To be precise, your gut pretty much runs from your mouth to the end of your intestines, which is your anus. However, most of the gut excitement centers more on the stomach and intestines.

Microbiome mania
A word that comes up frequently in the media these days is “microbiome.” Try dropping this word at the next cocktail party. What the heck is a microbiome, anyway? Your microbiome is your body’s unique collection of microbes — bacteria, viruses, fungi, and other microorganisms. These microbes (of which there are about 100 trillion!) are everywhere: on your skin, in your nose and mouth, and in your digestive and urinary tracts. The thought of all of these bacteria crawling on and inside you sounds creepy, for sure, but what’s important to understand is that your microbiome has a big influence on your health. Here are a few key points to know about your microbiome:


• Your microbiome is different from anyone else’s.

• You’ve inherited part of your microbiome from your mother, but a lot of it is determined by lifestyle factors.

• Researchers now believe that your microbiome is linked with many diseases, including diabetes, heart disease, cancer, and obesity. It’s also linked with allergies.

Inside your intestines
You might be surprised to learn that your gut contains as many as 1,000 different species of bacteria. The species depend on a number of factors. For example, a newborn has different types of bacteria than an 80-year-old man. Diet plays a big role in the type of bacteria found in the gut. Someone who eats a vegan diet will have different bacteria than someone whose diet focuses primary on animal protein. Also, where you live influences gut bacteria: A person from Japan will have different species than a person living in the United States.

Good vs. bad bacteria
Back in 2012, I wrote about probiotics, which are generally considered to be “good” bacteria. Probiotics help to restore balance to the gut, helping with digestion and possibly, as researchers are discovering, a number of health issues, including weight.

When there aren’t enough of the good bacteria in the gut, the bad bacteria can dominate and lead to a condition called dysbiosis, or a microbial imbalance. Dysbiosis is thought to be a factor with conditions such as irritable bowel syndrome, inflammatory bowel disease, allergies, and even obesity and diabetes. The more probiotics, or good bacteria, in your gut, the better your chances of avoiding these problems, according to the latest thinking.

Healthy gut = slimmer body
It seems a little incredible that bacteria could be responsible for one’s weight. Keep in mind that weight is dependent on many things, including genetic makeup, environment, health issues, and medicines, for example. What’s interesting, though, is that newer research that involves giving probiotic supplements to overweight people is looking very promising: In one study, published in the British Journal of Nutrition, obese women who took a probiotic supplement containing bacteria from the family Lactobacillus rhamnosus lost twice as much weight as women who took a placebo (inactive treatment). During the maintenance period, the probiotic-taking women continued to lose weight.

The researchers believe that the probiotic helped make the intestinal wall less permeable to substances that could lead to obesity and Type 2 diabetes. In addition, the probiotics helped the women better control their appetite. Unhealthy gut bacteria may also be responsible for those pesky food cravings by sending messages to the brain that you need to reach for that last chocolate doughnut.

Feeding your gut
Are the pounds magically going to melt off just by popping a probiotic supplement? It’s too soon to make that claim (although it would be nice!). Until we learn more, there are a few things you can do to keep your gut bacteria healthy and happy.

1. Include healthy gut foods in your eating plan. Gut-friendly foods include:

• Yogurt (look for the words “live and active cultures” on the container)

• Kefir, a yogurt-like drink filled with probiotics

• Buttermilk

• Sauerkraut, kimchi, and other pickled or fermented vegetables

• Soy products like soy milk, miso, tempeh, and soy sauce

• Sourdough bread

2. Feed your good bacteria with prebiotics, found in:

• Asparagus, artichokes, leeks, onion, garlic, chicory

• Berries and bananas

• Oatmeal

• Legumes (such as black beans, chickpeas, kidney beans, lentils)

3. Aim for between 25 to 38 grams of fiber each day. Fiber can promote the growth of good bacteria. Fruits, vegetables, legumes, and whole grains are foods that contain fiber.

4. Limit unhealthy, refined carbohydrate foods and fatty foods.

5. Get some exercise! Exercise can help boost the numbers of healthy bacteria in your gut, too.

6. Talk with a dietitian or your doctor about taking a probiotic supplement. There are different kinds out there, so you might want to choose one that contains different strains of bacteria instead of just one. Also, choose one with at least 10 billion CFUs (colony forming units). Don’t take a probiotic supplement if you have a suppressed immune system or if you are very ill.

  • Joe

    Excellent advice. One thing I would expand upon is that just as different people react to food and medicines differently, people react to various bacteria differently. I was an IBS sufferer for many years and tried a number of probiotics with little success. Lactobacilis Acidopholis – the bacteria commonly found in yogurt and most OTC probiotic fomulas did nothing for me. Kefir was a bit more helpful, probably because it usually contains a larger variety of bacteria, one brand boasts more than a dozen. However I finally got good results with a patented bacteria that was at the time only marketed through GI specialists. Today it’s available over-the-counter everywhere. I won’t make a specific recommendation, because I truly believe each person’s needs are unique, and it may not work for you, just as yogurt works for millions of people, but not for me.

    The other caveat -besides avoiding them if you have immune system issues- is that even generic formulas tend to be very expensive.

  • Al Lane

    I was wondering if it might be possible to overcome the problems of drinking too much diet sodas by switching to drinking filtered water?

    I do have some kidney disease that I am coping with.

    I love cheeses…but from what I have been told, the cheese contains a high level of phosphorus.



  • A. Campbell

    Hi Al,

    In my opinion, water is always a better choice than diet soda. There is some evidence that soda (both regular and diet) may be harmful to the kidneys. And yes, cheese does contain phosphorous. This doesn’t mean that you can’t ever eat cheese, but you will likely need to limit the amount. It’s best to ask your doctor or a renal dietitian about the amount of phosphorous that is safe for you.