The thin woman who received antibiotics and as a result developed a drug resistant strain of C. Difficile is interesting. They gave her a stool transplant which means they gave her the bacteria from an obese woman’s gut and after the procedure she no longer had the C. Difficile infection but had an insatiable appetite and gained over 30 pounds. While this type of evidence is dramatic it is pretty weak for proving causation. However, there are mice that are bred and housed to have no bacteria in their guts and when colonized with bacteria from obese mice, gain weight. In another study using the same type of mice they looked at female twins, one obese and one thin. When they transplanted the bacteria of obese women into these mice they increased weight but when they transplanted bacteria from their thin twins, they did not. Laboratory research has found that some gut bacteria can cause humans to release a certain hormone that makes people feel fuller while other bacteria can cause the opposite effect making people feel hungrier.
Is weight loss is outside of your control and dictated by microscopic organisms in your intestine? No, if you choose to exert control you can overcome the effects of the bacteria. However, it may be harder for one person to lose weight versus another because the feelings of cravings and hunger are in part determined by your gut bacteria. Lifestyle choices also seem to impact the types of bacteria you get. Healthy lifestyle choices with whole grains rather than diets with highly processed flours and simple sugars actually allow the bacteria that help you with feeling fuller to thrive because they actually survive by converting the non-digestible fiber into their energy source. You also have a much wider variety of bacteria to grow in your intestines. If you then switch to a high carbohydrate, highly processed diet you will reduce the concentrations of these helpful bacteria and cause a lesser variety of bacteria to grow once you change the make-up of your intestines, it will make it harder for you to lose weight. Think about it, when someone tries to switch from one type of diet to another, it is hard to do at first. Someone eating broccoli and kale who starts eating processed mac and cheese will initially feel ill while the same feeling occurs in people switching to a high fiber diet. Over time though your body gets used to it and part of that process is related to changes in the dominance of certain types of bacteria over others in your intestines.
Doctors are not recommending that obese people try to get a stool transplant to assist in weight loss. There are many species of bacteria and there are billions of bacteria. We are only in our infancy in figuring out the interrelationship between these bacteria and ourselves. What if one bacteria increases body weight but prevents the development of another disease by doing something else in the body. If you have a multidrug resistant bacteria and no other option, a stool transplant is a great option. It is possible that probiotics like those in active yogurt cultures may help but there is no convincing data that they do as of yet and it requires further study. For weight loss, just know that if you have had a hard time losing weight in the past that it may not just be your willpower that is undercutting you, it may be invisible microbes influencing you. Also know that as your diet takes hold that internally you are changing the concentrations of your intestinal bacteria which can help to make it easier to sustain that weight loss over time but this transition is going to take time.
Michael White; Dept. Of Pharmacy Practice, UConn School Of Pharmacy