Could Gut Bacteria Be The Reason You Can't Lose Weight?

Friendly, probiotic bacteria are astonishingly important to the health of their human hosts. Living mostly in the gut, these microbes keep pathogenic bacteria from establishing a foothold in the body. They multiply to provide bulk for stool, easing bowel movement. They convert harmful compounds in our food into nutrients, they synthesize anti-inflammatory agents, they make vitamins, they reduce the toxicity of gluten, and they synthesize sex hormones and neurotransmitters. A growing body of research finds that some strains of bacteria even help to keep us from gaining excess weight.

The problem is that other strains of bacteria may make it easier to put on belly fat than to take it off.

Icky Observations That Led to Discovery

Even though scientists recognized that Lactobacillus bacteria regulate serotonin levels in the 1920's, the observation that gut bacteria could have a relationship to belly fat is much more recent. Scientists noticed that lean lab rats that ate the droppings of obese lab rats developed obesity themselves, but feeding them the feces of lean lab rats helped them return to their normal weight. This disgusting form of a "fecal transplant" showed that there are clear categories of obesity-inducing and obesity-protective gut bacteria in mice.

Humans, however, have different feeding habits, and the roles of different species of bacteria in human obesity are not quite as clear. At first researchers looked for a relatively complicated explanation of the role of gut bacteria in weight control. A series of studies found that a higher ratio of Firmicutes bacteria, the "bad" gut bacteria, to Bacteroidetes bacteria, the "good" bacteria, was associated with obesity. Firmicutes bacteria form tough spores that can survive for long periods in dry conditions, and are the culprits in spoiling wine and beer. Bacteroidetes live in moist environments everywhere, in the soil, in water, on the skin of animals, and the human digestive tract, and can cause disease when the immune system is weak.

Later studies, however, found that the ratio of the two different kinds of bacteria was not as important as the total number of Firmicutes bacteria. However, these studies are correlational, not causational. They don't tell whether Firmicutes bacteria cause obesity or obese people tend to have more Firmicutes bacteria. Endocrinologist Dr. David Bell goes so far as to say that "in humans the changes in gut microbiota are an association with rather than the cause of obesity." However, we don't have to take the esteemed doctor's word for this. We can look at how things we can control affect our weight.

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Fecal Transplants, You Will Be Glad to Know, Don't Induce Weight Loss

Physicians in the Netherlands gave 18 obese men who had metabolic syndrome (prediabetes, high cholesterol, high triglycerides, and wide waistlines) fecal transplants from lean donors. The recipients of the healthy donors' gut bacteria did not lose weight, but they had better blood sugar control and lower triglycerides. These benefits stopped about 12 weeks after the fecal transplants, probably because the recipients did not change their diets. If introducing good bacteria can improve metabolic health, then can antibiotics worsen it?

Two Probiotic Strains Assist Weight Loss

How do we know that antibiotics cause weight gain? Actually we have billions of examples. American farmers have been giving their cows, pigs, chickens, and turkeys antibiotics for decades to encourage them to gain weight. If antibiotics didn't work for adding weight, farmers would not have been buying them for 50 years.

But how do we know antibiotics cause weight gain in humans? 

A study involving 164,000 children in Pennsylvania that was reported in October of 2015 in the International Journal of Obesity concluded that repeated antibiotic use in childhood was linked to greater weight in adolescence, and that children who are treated with antibiotics could have weight issues for the rest of their lives. 

By age 15, teens who had received antibiotics seven times or more in their preteen years weighed on average 3 pounds more than their peers who had not been treated with antibiotics. Dr. Brian Schwartz, a professor at the Johns Hopkins Bloomberg School of Public Health and a lead investigator for the study commented that "Our data suggest that every time we give an antibiotic to kids they gain weight faster over time." Repeated use of antibiotics changes the balance of bacteria in the digestive tract, which changes the way food is broken down, which changes the number of calories available to the human body.

All of this does not mean, however, that once you have been treated with antibiotics you are doomed to a life of easy weight gain.

Also in 2015 another study reported that giving obese participants in a clinical trial two daily doses of Lactobacillus curvatus HY7601 and Lactobacillus plantarum KY1032:

• Reduced body fat, and
• Reduced waist circumference, 
• Without decreasing food intake and
• Without increasing exercise.

Supplementing with these two good bacteria did not result in significant weight loss, but it improved triglyceride and LDL levels (reducing the amount of the smaller LDL particles associated with coronary artery disease) in the diabetic subjects in the trial. It is possible to reduce body fat without reducing weight, of course, by increasing muscle mass, although the study did not report changes in muscle mass in the test subjects, good or bad.

Lactobacillus plantarum is a common ingredient in many probiotic formulas. It may be that the benefits of Lactobacillus bacteria for metabolic health are limited to the exact strains used in the study, but it is likely that other forms of Lactobacillus plantarum and Lactobacillus curvatus will have a similar beneficial effect.

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How do you feed your helpful gut bacteria so that they help you normalize your weight?

The key ingredient in any gut bacteria diet is resistant starch carbs. Many dieters avoid carbohydrates, thinking they are unhealthy for the human body. Helpful gut bacteria, however, need resistant starch, the kind of starch that doesn't break down easily into sugar, as their primary food source. One of the best sources of resistant starch is potato starch, used in Europe the same way that corn starch is used in North America. Boiling (not roasting, baking, or frying) white potatoes creates the resistant starch that feeds good bacteria without raising blood sugar levels. Boiling white (but not brown) rice also creates resistant starch. Taking a Lactobacillus plantarum supplement and making sure to get at least one serving of boiled white potatoes or boiled white rice per day is a good start toward restoring bacterial balance so it is easier for you to lose weight.