Does This Bacteria Make Me Look Fat?

pelvic-painThe microbial world within us and its link to obesity

A patient I saw last week told me a story about being put on prophylactic antibiotics for recurrent bladder infections. Soon after taking this daily medicine she began to gain weight.  A lot of weight. In fact, over the next two years she gained over 90 pounds without any changes in diet or exercise. Her doctors told her there was no connection. However, when she discontinued the medication a few years later the pounds fell off just as quickly as they went on. Was there a connection?  She came to our clinic to inquire.

Bacteria and the Microbiome

Until recently, mainstream medicine did not acknowledge a relationship between the bacterial ecosystem in our bodies and our ability to gain or lose weight, though with new research this understanding is rapidly changing. We now know that the bacterial cells living in our body outnumber our own cells 10 to 1. These microbes collectively weigh about three pounds, roughly the weight of our own brain. This bacteria, along with an assortment of viruses and fungi, make up what is called the microbiome. The microbiome is an internal ecosystem that lives peacefully (mostly) within us and plays a role in our digestion, immune system, moods, and even our metabolism. This dynamic inner environment, where “good” bacteria keep “bad” bacteria in check, is in delicate balance and is easily affected by such things as taking antibiotics.

Why would the bacteria in our guts have anything to do with weight gain? 

It turns out that certain bacteria are better than others at breaking down the foods we eat. The more efficient bacteria are at extracting calories from food, the more energy we store as fat, and the more weight we put on.  Your skinny friend whom can seemingly eat whatever she wants and not gain a pound? She likely has less efficient bacteria living in her digestive tract than a heavier person. There also seems to be a link between our intestinal microbiome and appetite control and insulin resistance, which further complicates this picture.

Skinny bacteria vs Obese bacteria

Each person’s microbiome is their own “bacterial fingerprint,” and certain microbial profiles are associated with being obese, while others are found in more slender people. Your bacterial fingerprint is constantly subject to change and is affected by many things throughout the course of your life: your mother’s microbiome when you were born, whether you were delivered via vaginal birth or cesarean, environmental exposures, medications, diet, and so on. Interestingly, a recent study showed that when gut bacteria from human twins- one obese and one slender- were transferred to lean mice, the mice that received the obese bacteria rapidly gained weight, while the slender bacteria recipients stayed the same size.  Another study found that up to 20% of the weight that patients lose after gastric bypass surgery may be attributed simply to the shift in their intestinal microbiome following the procedure.

So how do you change your bacterial fingerprint to one favoring a healthy weight?

Unfortunately the jury is still out as to how to precisely manipulate the microbiome in this way, though the following tips can help promote healthy bacterial balance in your body, which may just help tip the scales in the right direction.

  1. Clean up your diet. “Bad” bacteria love sugar.  They also thrive on high fat, low fiber diets. Make sure you eat plenty of fresh, fiber-filled vegetables, while avoiding processed foods that are high in fat and sugar in order to support a proper balance of bacteria in your gut.
  1. Take antibiotics only when indicated. Read: not when you have a virus like the common cold, flu, or any type of viral lung or ear infection. Antibiotics will not have any effect against these pathogens and will only serve to quickly throw your body out of balance while contributing to the phenomenon of antibiotic resistance. This is not to say that antibiotics are inherently bad, as they can be lifesaving when used appropriately. Ask your doctor about supplementing with a high-quality probiotic if you do need to take antibiotics, in order to preserve your gut bacteria during treatment.
  1. Pick a good probiotic. Speaking of probiotics, emerging research indicates that they actually may be used to directly treat and prevent obesity. One study found that a high-dose probiotic, VSL#3, suppressed weight gain, improved insulin resistance, and lead to decreased food intake in mice. Another recent study showed that obese women on a low-calorie diet who took a daily probiotic containing L.rhamnosus achieved more sustained weight loss than women who took a placebo. Keep in mind that not all probiotics are created equal. Some cheaper varieties may not be able to survive the acidic environment of the stomach or may not contain enough live organisms to have any meaningful effect in the body. It is also important to pick a product with the right mixture of bacterial strains to fit your individual condition. Consult a naturopathic doctor to help you in choose the best product for you.
  1. Enrich your diet with fermented foods. Foods like sauerkraut, yogurt, kefir, kombucha and kimchi are all natural sources of beneficial bacteria. Look for labels that say the product contains live or active cultures when purchasing these in stores, or consider making these foods at home. Websites like and can be excellent resources to learn more about home fermentation practices.
  1. Choose organic, grass-fed meat. It should be no surprise that antibiotics can affect weight gain, as they have been given to livestock to quickly fatten them up before slaughter for years. In fact, 75% of all antibiotics consumed in the U.S. each year are given to commercial poultry, cows, and pigs. It is unclear exactly what happens in our bodies when we eat antibiotic-treated meat, but it is probably best to avoid this exposure if at all possible.
  1. Avoid antibacterial soaps and body washes. Antimicrobial soaps are found in households across the nation, yet there is actually no clear evidence that using these products is any more effective at preventing disease than good old fashioned soap and water. Antibacterial soaps have chemical products such as triclosan, which recent studies show may alter hormones in the body and may also contribute to bacterial resistance. The FDA and the EPA have both recently expressed concern about the widespread use of these products. Until more is known about antimicrobial soaps and their impact on the body (including their potential hormonal and metabolic-disrupting effects), it is probably best to avoid these products altogether.
  1. Consider lab testing to determine the health of your digestive tract. Specialized lab tests such as stool analysis and SIBO (Small Intestine Bacterial Overgrowth) breath testing can help determine if your intestinal microbiome is out of balance and can help guide treatment to restore healthy microflora. More information about SIBO and doctors who specialize in this type of testing and treatment can be found at and the NUNM SIBO-IBS Center website.
  2. Stay tuned! The intestinal microbiome is an exciting, rapidly expanding area of scientific research. With extensive government-funded studies such as the Human Microbiome Project, we are beginning to get a glimpse into the future of obesity prevention and treatment, which is an exciting new world indeed!

by Niki Rarig, student of Naturopathic and Classical Chinese Medicine NCNM  Edited by Dr Elise Schroeder


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