Can improving your gut health help with weight loss?

Gut health is important for your digestion, immune system, mental health, and more. Research suggests that improving the health of your gut can help with your weight loss goals. 

When you think of your gut, you might imagine a large organ with the sole purpose of removing the waste you produce from the foods you eat. But research has shown that the gut is a complex metabolic powerhouse that is vital for your overall health. 

It’s home to trillions of different microorganisms, including bacteria, fungi, viruses, and even parasites. Together, they form your gut microbiome. A healthy gut microbiome with many beneficial bacteria is important for good gut health — and everyone’s is unique.

At ZOE, we run the largest nutrition and gut microbiome study in the world. Our latest research has found strong links between specific gut microbes and body composition. 

We’ve found 15 “good” gut bugs associated with better health outcomes and 15 “bad” gut bugs linked with worse health, including excess weight. This groundbreaking research highlights the connections between people’s food choices, their gut bugs, and their overall health and weight. 

Healthy weight loss

Before you decide to go on any kind of diet, it’s important to consider your starting weight. If your body mass index (BMI) is within the underweight range, or at the lower end of the moderate range, you don’t need to lose weight.

We know that restrictive diets may lead to fast weight loss to begin with, but they don’t work in the long term

Our research shows that eating the right foods for your individual metabolism and your unique gut microbes is good for your metabolic health and your weight. Most importantly, it’s more sustainable for you and your overall health. 

The ZOE at-home test tells you which “good” and “bad” gut bugs live in your gut and helps you find the best foods for your body and your gut health.  

Unpublished research from ZOE shows that people who closely followed our personalized, gut-healthy nutrition program lost an average of 9.4 pounds after 3 months, and around 80% of participants didn’t feel hungry and had more energy.

Read on to learn more about how gut health is linked to weight.

How are gut health and weight linked?

Scientists have found that people with obesity have very different and often fewer bacteria in their guts, compared with people with a moderate weight. 

This is true even in twins and shows that the gut microbiome plays a greater role than genetics when it comes to weight. 

Exactly how your gut microbiome influences your weight is not entirely clear, but scientists are working on uncovering the details. 

In one study, mice received a collection of gut bugs from people with obesity. The mice put on weight and fat, and their metabolism and gut microbiomes changed.

But are there specific gut bacteria that are linked with weight? 

Gut bacteria and weight loss

There’s evidence to suggest that the specific bugs in your gut may be a good predictor of your chances of weight loss. 

Other research indicates that the ratio of different types of gut bugs in your microbiome could be important for weight management. 

In one study, researchers looked at links between the different bacteria in participants’ guts and how much weight they lost on a calorie-controlled diet. 

People who had more bacteria that belonged to a group called Prevotella compared with those that belonged to the Bacteroides group lost weight and body fat more easily than people who had equal amounts of these bacteria. 

In our own research, we’ve found that many of our 15 “good” gut bugs are linked with lower weight and less visceral — or belly — fat.

We also saw that one member of the Prevotella group, Prevotella copri, is associated with lower insulin levels. This is good for your overall health, as too much insulin increases your risk of obesity. 

Probiotics and weight loss

Given the links between gut bacteria, metabolic health, and weight loss, changing the balance of your gut microbiome to include more “good” bugs may help with weight loss naturally, rather than through restrictive dieting. One way of doing this could be with probiotics. 

According to the World Health Organization, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host." In short, they’re live microbes that could be good for gut health. 

Their potential benefits include aiding digestion and breaking down and producing useful nutrients and chemicals. Changing your microbiome to include more of the bugs that are linked with moderate weight may also help you lose weight naturally.

Many fermented foods — like yogurt, kefir, sauerkraut, and some aged cheeses — contain these live, probiotic bacteria.

Probiotic supplements that are currently on the market claim to mimic the benefits found in different foods. But there’s not enough good quality research at the moment to suggest they can help with weight loss.

At ZOE, we recommend including fermented foods that contain probiotics in your diet. It’s important that you eat these foods regularly to give them the best chance of setting up home in your gut and staying there. 

ZOE co-founder and leading microbiome expert Professor Tim Spector recommends “a small shot of fermented foods daily.” 

To look after your good gut bugs, you also need to feed them prebiotics, which act as fuel for them. Prebiotics are substances that occur naturally in plant and fiber-rich foods. 

Good sources of prebiotics that you can find in your kitchen include onions, leeks, garlic, asparagus, Jerusalem artichokes, oats, mushrooms, and whole grains. 

ZOE’s research has shown that how you respond to food is unique to you. As well as telling you about the bacteria that make up your gut microbiome, the ZOE at-home test can tell you which foods are your personal “gut boosters” that you should eat more of to improve your gut health, and which are your “gut suppressors” that you should eat less of. 

Eating with an understanding of your body’s responses can improve your overall health and, in turn, your weight. 


Research suggests that people with obesity have a smaller range of gut bugs than those with a moderate weight. This is linked to worse gut health.

Scientists have found that specific gut bugs and the balance between different types of bugs may influence how easily a person can manage their weight. 

ZOE research has linked many of the “good” gut bugs we’ve identified to lower weight and less belly fat and some of the “bad” bugs to increased weight and belly fat.

Helping your "good" gut bugs to thrive can improve your gut health and may also help with your weight management. 

Regularly eating fermented foods rich in probiotic bacteria — and plants containing the prebiotics that feed them — is one way to nourish your gut health. You can read more about the importance of gut health and how to improve yours here.

However, exactly how your body and your gut respond to particular foods is different for everyone.

Take the free ZOE quiz to find out more about your gut health and how to eat for your unique biology. 


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Cultured gut microbiota from twins discordant for obesity modulate adiposity and metabolic phenotypes in mice. Science. (2013).

Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. (2014).

Prevotella-to-Bacteroides ratio predicts body weight and fat loss success on 24-week diets varying in macronutrient composition and dietary fiber: results from a post-hoc analysis. International Journal of Obesity. (2018).

Probiotics for weight loss: a systematic review and meta-analysis. Nutrition Research. (2015).

Richness of human gut microbiome correlates with metabolic markers. Nature. (2013).

The intestinal microbiome predicts weight loss on a calorie-restricted diet and is associated with improved hepatic steatosis. Frontiers in Nutrition. (2021).