Why Gut Bacteria Is Important to Your Body Composition

July 28, 2016

When you hear the word "bacteria," it's probably a safe bet your mind goes to "eww" instead of "love it!!!". That's understandable: bacteria brings to mind "bacterial infection" followed by "antibiotic". To many people, bacteria = sick.

But did you know that right now, your entire body is host to trillions of bacteria, most of it essential to your health?

Much of this bacteria lives in your intestines and is referred to as your gut microbiome, what some scientists refer to as the forgotten organ. It's a way of grouping the trillions of bacteria that live inside you and carry out many essential processes in your body.

As it turns out many of these are helpful and can have a significant effect on your body composition and overall health.

Based on recent findings, it turns out that these little creatures inside us can do us a world of good for our overall health and body composition. In several cases, they are even downright necessary for optimum health — from potentially curbing obesity to regulating non-communicable inflammatory disorders to your current state of mind.

Despite all of this wonderful news, it is worth noting that we are still largely in the dark about what makes a healthy microbiome. Let’s take a look at what that might mean and why it’s worth thinking about when you’re trying to make changes to your body composition.

Gut Bacteria and Your Body Composition

You may be wondering if an individual's unique microbial makeup, just like one’s genetic makeup, can potentially influence body weight and composition.

If you are, you’re not alone - researchers are beginning to give questions like these more attention. With an estimated completion date in 2020, an ongoing observational study by Tufts University is aiming to answer the body composition connection by examining the role of gut microbiome on lean body mass and physical function among older adults.

However, since we can’t sit around and wait 4 years for Tufts University to get back to us, we'll consider a couple of recent research studies that strongly suggest how your gut microbiome can have a direct impact on overall body composition.

First, it has been found that transplanting intestinal microbiota from obese mice can increase total body fat in lean mice — a nearly 60% increase in body fat content within 14 days despite reduced food consumption. Insulin resistance accompanied the increase in body fat among the lean mice.

According to the researchers, these findings suggest that gut microbiota may be a significant factor that affects energy expenditure and storage (aka your metabolism) and fat storage. This is particularly important, given that your metabolism is closely linked to the state of your current body composition, not necessarily your age or even your diet, which is in contrast to common public perception.

The results from the above mice study is supported by additional studies on transplanting intestinal microbiota, this time around, among humans. In the study, males with metabolic syndrome (a collective name for signs and symptoms that increases your risk of stroke and diabetes) received infusions of intestinal microbiota from lean donors. After six weeks, recipients experienced increased insulin sensitivity.

What does increased insulin sensitivity have to do with body composition?

The more sensitive you are to insulin, the more likely it is that you have a leaner body. This is possible because of insulin’s anabolic properties — replenishing fuel stores by transporting glucose to your muscles and liver (and storing them as glycogen) from the carbohydrates you consumed as well as reducing the rate of protein degradation (for energy source) in muscles.

Quick note: Insulin’s positive impact to body composition becomes reduced when you begin living a sedentary lifestyle and/or consume highly processed carbs frequently. Instead, insulin starts to store glucose as fat. This state is known as insulin resistance.

The Key To A Healthy Gut: Diversity

So far, it seems to appear that not all gut microbiomes are created equal, and that lean and healthy people tend to have a "healthier gut." What might contribute to that healthy gut?

It has to do with how much bacterial diversity your gut has.

In 2009, microbial ecologist Maria Gloria Dominguez-Bello and her team visited the Yanomami tribe  — a tiny community of an isolated American-Indian group in the Brazilian Amazon. With oral, skin, and fecal samples from 34 Yanomami villagers, Dominguez-Bello revealed their findings six years later:

The average Yanomami's gut bacteria had more bacteria diversity than anyone from any other group, ever.

This finding came right on the heels of a similar one, the previous year, when it was reported that the gut microbiome of the Hadza hunter-gatherer tribe, an African indigenous tribe in Tanzania, had higher levels of microbial biodiversity than subjects living in urban areas and agricultural communities.

So tribes living in the Amazonian rain forest and African plains have more gut bacteria than people in urban New York or Paris - so what?

In 2016, the link between gut microbial diversity and its absence in some disease states was described in a study published in Molecular Metabolism. The researchers noted that overall health is compromised when there’s an absence of diversity in the gut bacteria resulting from lack of dietary diversity.

They further emphasized that having more diversity translates to a more varied repertoire of responses against different disease states. 

Who would have thought more bacteria in your body was a good thing?

Make Your Gut Microbes Work In Your Favor

Your microbial makeup has the ability to continuously shift and is influenced by (but not limited to) your diet, environment, and lifestyle. With this fact, you’ll likely wonder what type of diet and lifestyle supports a healthy gut microbiome.

Like most things in life, it all boils down to striving for balance by maintaining a lifestyle that helps the beneficial bacteria thrive. As reflected in the studies mentioned earlier, maintaining microbial diversity is also equally important. You can start off with the following steps!

Bring on the probiotics.

A probiotic is often referred to as friendly bacteria that help keep the bad guys (viruses and other bacteria) in check. Its health benefits range from boosting immunity to reducing cholesterol levels to keeping anxiety levels in check. Think of them as your personal army who have sworn to protect you 24/7.

So, how do you make sure that you have enough of them?

Consume yogurt (real yogurt that is) and fermented foods. Traditional cultures have their own version of fermented goodness — from Korea’s kimchi to Russia’s sauerkraut. If fermented foods are not your thing, consider probiotic supplements.

Fill up on fiber.

You can also help the good guys thrive in your gut by consuming prebiotics. Generally, prebiotics are a form of soluble fiber.

Your body cannot digest these prebiotics, but your gut bacteria can. Good sources of prebiotics include leeks, garlic, onions, fruits, legumes, and raw chicory. Resistant starches such as plantains, green bananas, and cooled potatoes have been shown to boost beneficial bacteria in the colon in animal studies.

Skip the antibiotics when you can.

Antibiotics are designed to cure bacterial infections by killing the invading bacteria. Unfortunately, antibiotics can't really separate the good bacteria from the bad. As a result, antibiotic therapy can significantly reduce your microbial population as well as its diversity.

You don't even need to be on a long-term regimen for this to occur. In fact, three to four days of antibiotics can already alter your gut microbe population and diversity. Studies have shown that children are particularly at risk as reduced gut bacteria diversity has been linked with childhood obesity, which significantly puts them at risk for being obese as adults.

For this reason, avoid using antibiotics as a first line of defense for common infections like colds and the flu.

Steer clear from conventionally-raised meats and poultry.

It’s no secret that antibiotics are often used to speed growth among livestock. While this might help farmers and their buyers meet their bottom lines, this amounts to overuse of antibiotics that encourages the development of antibiotic-resistant bacteria.  

A George Washington University study found out that this practice is more likely to transmit antibiotic-resistant K. pneumoniae - a bacteria that causes damage to the lungs - to humans than clinical isolates of antibiotics. 

While buying organically-raised meats may be more expensive, you don’t have to break the bank by using meat as a condiment and opting for vegetables as the star of your meals.

Spend more time outdoors.

Spending time outdoors regularly can help increase your exposure to microbial diversity. If possible, start a garden! Getting your hands dirty with soil will reacquaint your gut flora with its long-lost members.

So you’re a germaphobe when it comes to keeping yourself and your loved ones free from germs? The idea behind the Hygiene Hypothesis is worth reading.

The Takeaway

Your invisible gut microbes can potentially help you shape your body composition for the better and promote optimum health through diversity. You can accomplish this by making an effort to keep those good gut bugs plump with prebiotics and thriving through probiotics.

All of this underscores that when it comes to improving body composition, nutrition plays an incredibly significant role. While energy balance is still critical to take into account - how much energy you take in vs. how much you expend - this research on your gut microbiome indicates what you eat can also encourage and support your efforts to change your body composition.

It’s high time that we shift our mindset of microbes and bacteria as being filthy and infectious to friendly critters that can help us lead healthier lives, including helping us improve and maintain a healthy body composition.


Kyjean Tomboc is a nurse turned freelance healthcare copywriter and UX researcher.  After experimenting with going paleo and vegetarian, she realized that it all boils down to eating real food.