The Link Between Gut Health and Obesity

If you’re like over 73% of the population and struggle with being overweight or obese, you may want to look more closely at the bugs in your gut. These trillions of bacteria, fungi, parasites, and viruses could be a hidden key to your weight loss journey.

Let’s examine the role gut bacteria play in your health, how they can influence your weight, and what kinds of changes you can make to improve your gut bacteria.

What is gut bacteria?

Your gut microbiome consists of trillions of microbes that live in your digestive tract. In fact, our bodies have many more genes from our gut bacteria than from our human cells. 

The gut microbiome is often referred to as our “second brain.” Each person’s gut microbiome is unique, like a microbial fingerprint, and is shaped by both your genetics and your environment. 

Your microbiome begins to develop in infancy. It is affected by your mother’s health, your type of birth (vaginal or cesarean), your breastfeeding history, and many additional factors including your geography, diet, and medication use. 

Having an entire ecosystem of microscopic organisms in our bodies may sound concerning. But in fact, many of these organisms are essential to our health. They help with the immune system, digesting food, producing hormones that help control appetite, and synthesizing vitamins and essential nutrients including short chain fatty acids (SCFAs).

How does gut bacteria affect weight?

Your gut bacteria can affect your weight. For example, your microbiome influences how food is digested and absorbed and how dietary fats are stored in your body.

Your microbiome may also impact the production of hunger hormones, such as ghrelin, which control if you feel hungry or full. An unhealthy gut microbiome can increase inflammatory markers, which may lead to weight gain and metabolic disease. 

Can obesity be caused by poor gut health?

Yes, in part. It’s not the whole picture, but science continues to emerge showing that poor gut health or “dysbiosis” can contribute to obesity. “Dysbiosis” refers to an unhealthy balance of gut microbes, and often signals that there is a decrease in microbial diversity and a shift in the balance between “healthy” and “unhealthy” microbes.

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Even though obesity is most often linked to multiple factors, we now know that gut flora is likely part of the cause. A landmark study in 2006 showed that when scientists transplantated the stool of obese mice into germ-free mice, they became obese. However, when they transplanted the stool of lean mice into similarly germ-free mice, they did not. 

A later study in 2013 studied the stool from human twins — one obese and one lean — and showed that transplanting stool from the obese twin into germ-free mice led to increased fat mass in the mice, but this did not occur when transplanting stool from the lean twin. 

How can I tell if I have a healthy gut microbiome?

In general, we know that a healthy gut includes high microbial diversity and high levels of certain microbes including Akkermansia and Bifidobacteria. However, what defines a healthy microbiome is still not fully understood. Whether a particular microbe is healthy or harmful depends on the complex environment around it including what other microbes are present at the time. 

You may want to talk with your healthcare provider about the best way for you to test the health of your gut microbiome. The good news is that even without doing any testing of your microbiome, there are actions you can take to start improving your gut health now. 

How can I improve my gut bacteria?

You can start improving the health of your gut bacteria today, particularly through making changes in your diet and lifestyle. The following changes may help improve the health of your microbiome: 

• Increase fiber in your diet. Aim for about 30 grams of fiber per day through high fiber foods such as fruits, vegetables, seeds, nuts, and legumes. Fiber helps feed healthy gut bacteria, and leads to the production of short chain fatty acids (SCFAs), which are important for health and weight control.

• Exercise more often. Exercise improves the health of the microbiome by increasing diversity and healthy gut bacteria. It is also generally recommended for weight loss.

• Review your medications with your healthcare provider to see if they might impact your microbiome. Avoid unnecessary antibiotics, and look at common medications that may negatively impact your microbiome such as non-steroidal anti-inflammatory drugs and proton-pump inhibitors. Some medications, such as Metformin, may have beneficial effects.

• Add more fermented foods to your diet. Fermented foods have high levels of probiotics, or “healthy bacteria” and include foods such as yogurt, sauerkraut, miso, kimchi, and kombucha.

• Include more polyphenols in your diet. Polyphenols help by feeding healthy bacteria and keeping your gut microbes in balance. They are found in foods such as berries, red wine, dark chocolate, coffee, and tea. 

• Consider discussing certain supplements with your healthcare provider. Some you might want to consider include probiotics, prebiotics, or synbiotics.

• Avoid artificial sweeteners. These can lead to dysbiosis.

Will the gut microbiome play a larger role in obesity treatment in the future?

Weight loss treatments are evolving, and it may be that the future of obesity treatment is in the microbiome. 

For example, studies are looking at the role of fecal microbiota transplant (FMT) for weight loss. This is a procedure where healthy gut microbes from a normal weight person are transferred to an obese person. So far these studies have been small and have not led to definitive conclusions. 

There are also early and small studies suggesting that supplementation with specific microbes, such as Akkermansia muciniphila, could lead to improved metabolic markers.

Why trust our experts?

Written by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a focus on chronic care management, women’s health, and mental health. She’s the co-author of “Open Heart: When Open-Heart Surgery Becomes Your Best Option.”.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

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Your gut has trillions of microbes that impact your health in many ways, including your weight. Improving the health of your microbiome now could help you lose some unwanted pounds. As the science continues to evolve, we may see that the future of obesity treatment is in your gut.