The Connection Between Obesity and Bad Gut Bacteria

How Obesity is Connected to Gut Bacteria

I can still remember being overweight as a young adult and I would have given anything to be able to take a pill to make the pounds fly away. So, I guess it’s no surprise that get-slim-quick pills and miracle fat burning creams are a mainstay on late-night TV advertising.

Although losing weight will never be as easy as simply popping a probiotic, there is some really exciting research coming out that links the composition of one’s gut bacteria to obesity and some of the deadly health conditions that go along with it. Ensuring the health of beneficial gut bacteria can assist us in reaching and maintaining a healthy weight. With obesity overtaking smoking as the United States’ #1 killer, who could have imagined that the next major breakthrough in public health could reside in our digestive tracts?

Different Bacteria in the Guts of Obese People

There are about one hundred trillion bacteria in the digestive tracts of adults. These bacteria perform a variety of very important functions for us, which our bodies cannot do as effectively without them. They assist in food digestion and produce vitamins and enzymes that break down and utilize the energy and nutrition in the food we eat. The good bacteria (the probiotics) in our gut assist our immune system in fighting off dangerous, disease-causing pathogens. They can calm the nervous system and can reduce allergies. There are many different strains of bacteria that can inhabit the human gut and the different strains have different effects on human health – some beneficial and some harmful. In a healthy gut, the beneficial bacteria compete for resources and crowd out the less healthy ones.

Many studies have confirmed that obese people, as compared to thin people, tend to have fewer numbers overall of bacteria and a lower diversity of healthy species in their digestive tracts. In one long-term study, an international team of scientists performed a thorough examination of the bacteria residing in the gut of Danish volunteers over a nine (9) year period. About half were obese and half were of a healthy weight at the start. On average, the leaner volunteers had a much higher microbial diversity and also had a great number of bacteria, about 40% more. Many of the obese volunteers were missing several strains of beneficial bacteria that are normally found in healthy guts.

The researchers periodically examined the volunteers’ gut flora for the duration of the study. They noted that for the obese participants only, those with lowest bacterial diversity were much more likely than those with higher bacterial diversity to gain weight throughout the course of study.

One particular finding has major implications for public health. Metabolic syndrome is the name of a group of symptoms that raise a person’s risk for heart disease, stroke, cancer or Type 2 diabetes. Each additional metabolic syndrome symptom a person has further increases their risk for these diseases. Metabolic syndrome symptoms include:

A large waistline (abdominal obesity)
A high triglyceride level or being medicated for high triglycerides
A low HDL (the good cholesterol) level
High blood pressure or being medicated for high blood pressure
High fasting blood sugar or being medicated for high blood sugar

Those volunteers with the lowest bacterial diversity (both in number and variety), regardless of whether they were obese or lean, were most likely to have insulin resistance and/or inflammation, which are symptoms of Metabolic Syndrome. Having a low diversity of bacteria in the gut, with its tendency for both lean and obese individuals, appears to be associated with an increased risk of getting a potentially deadly disease.

The researchers identified eight species of healthy bacteria missing from the digestive tract of the obese volunteers and speculated that perhaps someday a probiotic supplement of these species could be given to recolonize the gut.

Do Gut Bugs Play a Role in Causing Obesity?

If having a lower bacterial diversity of the gut is associated with obesity and related illnesses, is it the obesity that causes the lowered diversity or the lowered diversity that causes the obesity? Or perhaps is some other factor causing both conditions? Scientists are currently looking into this question. Recent research has shown that gut bacteria do play a role in the development of obesity.

Dr. Peter Turnbaugh and his colleagues at Washington University evaluated the microbiomes (mix of bacteria in the gut) of obese and lean mice and humans. They found that that obesity is associated with changes in the relative abundance of the two dominant bacterial divisions in the gut, the Bacteroidetes and the Firmicutes. For those study participants with the “obese” mix of gut bacteria containing a higher percentage of Firmicutes, they were more efficient at harvesting energy from the food they ate than were those participants with the lean mix of bacteria that is higher in Bacteroidetes. Excess energy is converted by the body to fat. This increased capacity for an “obese gut” to harvest energy might be a good thing in times of famine, but can cause health problems and unhappiness in our current times of relative abundance.

A 2008 Finnish study determined that in children, the deviations from the mix of gut bacteria that typically make up a healthy gut came before increases in weight.

The study found that those children with higher numbers of the Bacteroidetes family bacteria, rather than from the Bifidobacterium family, in their gut were more likely to become obese later on. Those children with higher numbers of the genus Bifidobacterium were more likely to remain normal weight. Having been breastfed is associated with having a reduced likelihood of becoming obese later on1. Bifidobacterium are the genus of bacteria that are normally transferred from the mother to the baby through breastfeeding and are prevalent in the gut of healthy breastfed babies2.

Because the alterations from the microbiome of bacteria that typically make up the healthy digestive tract precede the obesity, this seems to suggest that the gut bugs are somehow triggering the weight gain. The Finnish researchers believe that the Bifidobacterium that infants receive from their mothers through breastfeeding may help them to remain at a healthy weight.

Doctors at Washington University’s School of Medicine developed a very ingenious experiment that was first published in the journal Science to further study the question of whether bacteria can influence weight gain or vice versa. To prepare, they located pairs of identical and fraternal twins, where one twin was obese and the other lean – not an easy feat to find them since there is often a genetic component to obesity. They also raised genetically identical mice in a sterile environment to keep their guts free from microbes, to ensure that pre-existing microflora living in the mice were not affecting the study’s results.

Next, for each twin group the researchers transferred the gut bacteria from the obese twin into one group of sterile mice and the gut bacteria from the thin twin into a different group of sterile mice. Surprise, surprise, in each case the mice that received the bacteria from the obese twin gained significantly more weight (15 – 17% more) over the 5 week period of study than the mice given the bacteria from the lean twin – even though all of the mice were given ate the same amount and type of food.

Maybe our standard belief that “a calorie is just a calorie” isn’t so true after all. That some mice gained weight while eating the exactly same amount and type of food that other mice that didn’t gain weight also ate lends support to the many people who complain that they gain weight even when eating less than and exercising the same amount as their thinner friends and family members. Some folks’ mix of gut bacteria are likely more efficient at converting food to energy and fat than other’s.

Those mice that received the obese twin’s bacteria also showed changes that are associated with metabolic syndrome in humans.

Since the researchers were aware that in real life obesity is caused by not just bacteria, but also genetics and environmental factors (food and exercise), they decided to see what impact diet might have on the two groups of mice when they caged them together. Mice like to eat each other’s poo – a natural, spontaneous form of fecal transplant that is also undertaken by dogs – particularly when the poo is of the cat variety.

The researchers created two types of mouse food pellets based on a study of the average American diet. One pellet was based on the American diet at the healthy end of the spectrum with the highest intake of fruits, vegetables and fiber and with low levels of saturated fats. The other pellet was based on the unhealthy, opposite end of the spectrum with lots of fat and little fruits and vegetables. One group in one cage (containing ½ mice with “lean” bacteria and ½ with “obese” bacteria) was fed the healthy pellets and the other group in a different cage (also containing ½ mice with “lean” bacteria and ½ with “obese” bacteria) was given the high-fat, low-fiber pellets. The fat mice given the unhealthy pellets kept their unhealthy, original bacteria – the bacteria from their thin cage mates did not take over. However, for the group fed with the low-fat, high veg pellets, the bacteria from the thin mice took over for all mice in the cage with resulting weight loss and improved health (fewer symptoms of metabolic syndrome).

Lead researcher Dr. Jeffrey Gordon, of Washington University in St Louis, speculates that the reason that the lean bacteria could move in and take over is because of the reduced number of bacteria that are present in obese guts. He calls the extra space in a bacteria deficient gut a “job vacancy” and says studies in this area have shown that a person with more vacancies may see them filled by good bacteria, if they are fed a proper low-fat, high-fiber diet.

Probiotic (healthy) bacteria are not magic creatures that can turn mice thin all by themselves, but instead require a reasonably healthy diet to be able to thrive and provide their slimming benefits. Our gut bacteria and what we eat are interconnected as it relates to obesity. Fruits and vegetables are prebiotics, meaning that they provide indigestible fiber that healthy bacteria eat. It makes sense that the healthy bacteria that support thinness can thrive when their host feeds them right. This is one of the reasons that eating healthy causes weight loss (in addition to consumer fewer calories, for example). The future success of introducing the right bacteria to promote thinness in obese patients will likely only work with ongoing support of a diet that enables those bacteria to thrive. In other words, we must feed our healthy gut bugs.

How to Promote “Thin” Bacteria

Probiotic Supplements

The science is still out as to whether giving people probiotic pill supplements could help them to attain or maintain a healthy weight and body fat percentage. A few studies that have been done to date show promising results, however.

There was a Finnish study undertaken by Dr. Kirsi Laitinen that gave probiotic supplements in capsules to pregnant woman during and subsequent to pregnancy and found that the probiotics were helpful in preventing weight gain, particularly abdominal fat. The researchers gave the pregnant women Lactobacillus rhamnosus (L. rhamnosus) and Bifidobacterium lactis (B. lactis) supplements from the first trimester until they stopped breastfeeding. The results showed that the women who received the probiotics had lower fat percentages overall and less abdominal fat in particular than the placebo groups. Central obesity (high belly fat) was diagnosed in 25% of the women who had received the probiotics as compared to 43% in the women who did not receive them. This is particularly exciting as belly fat is considered to be particularly unhealthy, and is one of the signs of metabolic syndrome, as discussed above.

In a 2011 Korean study, researchers fed mice a high fat diet to cause them to gain weight. Subsequently, they put the mice back on a standard diet and gave one group of mice a probiotic supplement containing Bifidobacteria pseudocatenulatum (B. pseudocatenulatum) and two sub-types of Bifidobacterium longum (B. longum). The mice given the supplement, as opposed to the control group that did not receive it, showed significantly decreased overall weight and fat content.

In a study published in 2014 in the British Journal of Nutrition by a team of researchers headed by Université Laval Professor Angelo Tremblay, researchers showed that for women following a weight-loss (reduced calorie) diet, those who took a probiotic supplement lost more weight than the control group. The 125 study subjects followed a twelve week weight-loss diet followed by a twelve week weight-maintenance-diet. Half of the subjects were randomly assigned to receive a supplement of Lactobacillus rhamnosus during the study. For the men in the study, there was no difference in weight loss between the control group and the probiotic group. However, for the female study participants, those women who took the probiotic lost on average 4.4 kg while the control group lost only 2.6 kg after the initial 12 week weight loss diet. What was really interesting was that the women taking the probiotics continued to lose weight during the 12 week weight-maintenance-diet period for an average total loss of 5.2 kg – and the control group did not lose weight on average during the corresponding period. The researchers did not have a theory as to why the probiotics did not promote weight loss for men in the same way. However, as this study only looked at one particular probiotic strain, there is a lot of potential for future research and positive results in the area of probiotics as a support for weight loss when accompanied by diet.

Sadly, probiotic supplements as an aid for weight control is likely several years off. Currently, scientists are in the process of trying to determine which particular bacteria are those most closely associated with thinness. The doctors working on this question expect that it will take many years to isolate them and learn to culture them so that probiotic supplements can be made and sold to people who have struggle with weight loss or have persistent metabolic syndrome.

Additionally, probiotic pill supplementation is not a guaranteed fix for gut bacterial issues. There are potential challenges with administering probiotics in this manner. Many bacteria are not shelf stable and must be refrigerated to survive. Even they are refrigerated after purchase, it is hard to know at what temperature they were stored and maintained while warehoused and in transit. As the probiotics are living cells, they may start to die over time and hence must be fresh for maximum effectiveness. Certain manufacturers claim that their supplements contain high levels of colony producing bacteria, but tests done on them show the actual bacterial content to be much lower than the product claims. The small intestine contains Hydrochloric Acid as part of the digestive process and it is not clear whether enough probiotic bacteria can survive the trip to the lower intestine, where they are needed, to be effective. However, purchasing fresh probiotics made by reputable manufacturers from reputable retailers will prevent many of these problems.

Fecal Transplant

In the meantime, while the supplements are in the development phase, it might be possible to try a more crude experiment involving fecal transplant to assist people who are desperate to lose weight and willing to participate in a research study. In such a study, obese volunteers would receive a feces sample from a thin human donor to see if the ‘thin” bacteria that is physically introduced into their digestive tracts (via colonoscopy, a tube inserted into nose and down the digestive tract or a feces-containing pill and not, like the mice, by eating their cage-mates poo!) could take over and improve their health. As this is an experiment with the potential risks of inadvertently transmitting disease from the donor, it would likely only be attempted in extreme situations, for example for patients with failed weight loss surgery. There is some hope that fecal transplant could be effective in obesity. Fecal transplants have been successfully cured patients in extreme cases of Clostridium difficile (C. difficile), a potentially deadly, antibiotic-resistant bacterial infection.

Diet

It has been shown that eating a low calorie, low saturated fat and high fiber diet can increase the diversity of healthy microbes in the gut. More good bacteria, mean that there are more helpful bacteria working for you, doing the things that healthy gut bugs do to improve well-being. This can improve your immune system, potentially decrease allergies, elevate mood, reduce anxiety, help you digest the important nutrients in your food and synthesize necessary vitamins and amino acids. This seems like plenty of incentive to eat well, in addition to other benefits of eating a low fat, high-fiber diet i.e. potential weight loss and reduction of Metabolic Syndrome symptoms.

Good bacteria require a diet containing proper food for them to live. Prebiotics, the non-digestible foods that make their way through our digestive system and help good bacteria grow and flourish are the food that your healthy gut bugs need to thrive. Prebiotics include fruits, vegetables, whole grains and fermented foods such as kimchi, certain cheeses, kefir, yoghurt and miso. Ensuring a prebiotic rich diet, gives the healthy, “thin” gut bugs the chance to move in to a bacteria poor, obese gut and multiply – squeezing out the bad guys in the process.

Antibiotics

Antibiotic use may impact obesity. Infants given antibiotics early in life gained more weight than their peers who did not take them. Taking them can alter the mix of healthy bacteria in the gut and has been shown to affect fat levels in mice. Additionally, livestock are given low-dose antibiotics in their feed for the sole purpose of getting them to gain weight. Further study is being done to see how taking them may trigger obesity in humans. Fortunately, professionals in the medical community are becoming aware of the risks of over prescribing of antibiotics and are less willing to prescribe them in cases where they will be of limited benefit, such as for a lingering virus.

Final Thoughts

The Huffington Post recently featured an inspirational video dance performance. The female star is an incredible dancer who is clearly physically fit, but weighs 350 pounds. The accompanying article entitled, “Proof That You Can Be A Wildly Talented Dancer At Any Size,” mentioned that Whitney Thore had started dancing at age 4 and was a dance instructor by age 16. While she was in college, she suddenly started gaining a lot of weight inexplicably, she tells the author. You can’t dance that well without plenty of practice and practicing a very physical dance routine entails some serious exercise. Given the sudden onset of her weight gain and her evident high level of physical activity, made me wonder if there was some other factor, in addition to the polycystic ovarian syndrome she was diagnosed with, that might have contributed to her sudden weight gain. Could something have happened to affect the mix of bacteria in her gut? Perhaps antibiotics or illness? If so, could it be partially reversed to support her in losing weight? There might be no connection at all in this case, but for people like Whitney, who are not couch potatoes, but clearly struggle with their weight, I can’t help but think that the gut bacteria – obesity link could be a possible explanation and a source of hope.

Although I dreamed of a magic pill to melt my fat when I was younger, it does not appear that probiotics are that elusive cure. Diet and exercise are critically important to maintaining a healthy weight and in preventing Metabolic Syndrome and the diseases associated with it. However, the right composition of the gut bacteria does hold a lot of promise in helping certain folks who struggle to lose weight, even when doing everything they are supposed to. It can also support all of us in our efforts to maintain a healthy weight and prevent the diseases associated with obesity. Gut bugs are only one, of several contributors to obesity, but understanding their role can assist in the battle to improve public health.