The rate of obesity has more than tripled since 1975, and there are a great deal of theories as to why it has. Some experts think that at least one of the contributing factors to this epidemic is widespread changes in the human microbiome.

Our “microbiome” is made up of all the microscopic organisms that live in our body. Though we tend to only hear about bacteria when it’s causing an illness, many more bacterial cells are naturally found in a healthy body. In fact, there are more bacterial cells in our bodies than human cells! One to three percent of our total weight is even thought to come from these little buggers, so in a way, they actually are us!

The greatest number of these bacteria are concentrated in our gut, which contains tens of trillions of them. There, they are mostly concentrated in a part of the large intestine called the "cecum." They are also quite a diverse group, consisting of between 300 and 500 different species and adding almost 2 million genes to our genetic repertoire.

Though good gut bacteria is essential for proper digestion and optimal health, evidence is beginning to suggest that an imbalance in the concentration of these tiny organisms, technically called dysbiosis," could cause some big problems. Some of the roles these bacteria play in our health include producing certain vitamins and communicating with our immune system to help fight infection.

Our gut bacteria also seem to play a huge role in creating and sustaining obesity. One study suggested that obese people have more lipopolysaccharides, a type of bacteria that feeds on fat. Lipopolysaccharides can then cause inflammation, which can contribute to more weight gain.

Gut bacteria also seems to play a role in how our foods are digested and how full we feel. For example, a type of bacteria called a Firmicute has been shown to impair our glucose tolerance and cause us to metabolize fat more quickly, thus increasing our risk of weight gain.

One study showed that obese people had more Firmicutes, while lean people had more of a different kind of bacteria called Bacteroidetes. Eating more fat seems to encourages the growth of these firmicutes; so, the more fat you eat, the better your body gets at absorbing it!

A study done on mice yielded even more interesting results; when gut bacteria of obese mice were transferred to lean mice, the lean mice gained weight! Even more fascinatingly, the same effect was found when gut bacteria from obese people were transferred to mice. On the other hand, when mice were given "good" bacteria like bifidobacteria, clostridia, christensenellaceae, and akkermansia, their inflammation and body weight decreased!

Other studies have shown that among patients instructed to follow the same high-fiber diet, those who had more prevotella in their intestines lost much more weight than those who had more bacteroides. Another study showed that people who harbored high levels of a microbe called phascolarctobacterium were much more likely to be able to lose five percent of their body than those who had high levels of one called dialister.

The type of gut bacteria you have also seems to affect how much of certain hormones your body produces, which can in turn affect your appetite. For instance, H. pylori, a bacteria best known for causing ulcers, can also help lower ghrelin levels.

Differences in gut bacteria are thus a potential explanation for why different people seem to absorb differing amounts of calories from the same food, why some people seem to lose weight at such different rates on the same diet, and why it is so difficult for some people to lose weight and keep it off.

Gut bacteria still doesn't determine everything; some mice were more affected by the abnormalities in their microbiomes than others. However, the effects of abnormalities in our gut bacteria go far beyond weight; they have also been implicated in colorectal cancer, IBS, autism, chronic fatigue syndrome, type 1 and 2 diabetes, and Alzheimer's disease.

Having a favorable microbiome may also reduce your risk of certain infections, improve your recovery from a spinal cord injury, and increase the effectiveness of certain cancer treatments.

So what factors go into determining the makeup of our ultra-important microbiome? We inherit some of these gut bacteria from our mother, so changes in microbiome brought on by a bad diet could presumably get passed down over generations!

Evidence suggests that our microbiomes can also be altered by certain medications, including hay fever medication and hormones used for birth control or treating menopause symptoms.

A far bigger culprit may be antibiotics, which have been over-prescribed by doctors and irresponsibly used by the food industry. Rates of obesity even seem to be directly correlated with rates of antibiotic use in livestock. Additionally, studies have found that antibiotic use in mice was linked to fat gain, as well as that children who were exposed early in life to antibiotics were found to have a higher risk of obesity.

However, our diet and lifestyle also play a huge role in determining the makeup of our microbiomes, and changing our diets for as few as two days could cause their composition to change drastically. Yet maintaining those changes long-term will probably require dramatic changes in diet rather than minor adjustments.

Since lean people have more diverse gut bacteria, it's important to eat a diverse range of whole foods to encourage the growth of different kinds of organisms. You should also make a particular effort to eat more fiber and prebiotics, which provide food for the good bacteria in your gut. Some natural prebiotics include garlic, honey, onions, leeks, asparagus, apples, konjac root, and cocoa.

Luckily, the 123Diet can help you make your way to a healthier gut with our new vegan protein powder! It contains resistant starch, a prebiotic which has been shown to play a specific role in fostering the growth of good gut bacteria as well as to help control blood sugar levels.

Notably, people who had more hydrogen in their breath, indicating more gut bacterial fermentation, experienced less hunger. You should thus also make an effort to eat more fermented and probiotic foods, which contain live good bacteria that can help you feel more satiated and help crowd out the bad guys. Some good options include yogurt, kombucha, kefir, sauerkraut, tempeh, kimchi, miso, pickles, and certain types of cheese.

Though they are not a part of the 123Diet, nuts and seeds have also shown potentially beneficial effects on the microbiome. On the other hand, a diet high in sugar and fat can cause more unhealthy bacteria to take root. Interestingly, artificial sweeteners can have a similar effect.

Healthy fats like omega-3 fatty acid also seem to correlate with gut microbiome diversity, whereas a high intake of unhealthy fats has been associated with colitis and dysbiosis in mice.

Additionally, though whole grains are certainly a better option than refined grain products, increased intake of them has been associated with increased levels of the bacteria prevotella, which has in turn been associated with inflammation and rheumatoid arthritis.

There is also compelling evidence that exercise can positively influence the composition of our microbiota as well. However, these positive effects faded soon after the subjects stopped exercising, so you've gotta stay with it!

Weight loss surgery also seems to change the microbiome long-term, so there may eventually come a day where you can take a pill full of fat-fighting super-bugs rather than undergo a painful and dangerous procedure.

If you’ve really curious about what’s going on in your gut, you can have your microbiome analyzed by a company like Viome or an initiative like The American Gut Project. However, for most people, a commonsense diet that eliminates processed foods in favor of whole ones could go a long way towards getting your gut back in tip top shape.

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