Many people wonder if probiotics can help with weight loss. The answer lies in your gut microbiome, which is unique to you and is made up of the trillions of microbes that live within your digestive system.
It includes live bacteria, fungi, parasites, and other microbes. Some of these microbes are good for your health, while others are bad for your health.
Importantly, research has found a number of links between the gut microbiome and weight. People who carry extra weight have significantly different microbiomes to those who do not.
ZOE’s PREDICT program — the largest nutritional study of its kind, which has collected data on over 10,000 people — found that increased amounts of belly fat are associated with certain “bad” gut bacteria.
In order to increase your gut diversity, and therefore accumulate more “good” microbes, you can consume probiotics. These are live microbes that scientists believe may provide health benefits.
Some fermented foods are probiotic and contain strains of these microbes.
Probiotics also come as supplements in tablet or capsule form, but it’s unclear whether those currently on the market are effective at boosting your “good” bacteria.
You may have also heard of prebiotics. Think of them as food for the microbes in your gut. Consuming prebiotics can make your gut a more hospitable place where “good” bugs thrive.
ZOE’s PREDICT program has also shown that everyone responds differently to food. Discovering how to eat the right food for your body and gut microbiome can improve your overall health and, in turn, your weight.
How do gut bacteria influence body weight?
How gut bacteria influence body weight is not fully understood, but people with overweight or obesity tend to have significantly different microbiomes to people with moderate weight.
In fact, scientists have found that after transplanting gut microbes from people with obesity into mice, the mice then developed obesity.
One possible explanation is that the microbiome may influence weight gain through the gut-brain axis. This is the chemical signaling that happens between your brain and your gut, which can lead to hormone release that causes responses such as hunger.
This may explain why you might feel more hungry when you’re stressed, for example.
It’s therefore possible that if you change your gut microbes, you could change your weight.
Increased belly fat has also been linked to the 15 “bad” bugs ZOE identified in the PREDICT study. These bugs are associated with dietary inflammation, which is linked to weight gain and obesity.
How do probiotics help with weight loss?
Because of the links between the microbiome and weight that scientists have identified, changing the balance of the microbes in the gut to favor good bugs may help with weight loss.
However, it is not clear how or whether this actually works at this point. There are other theories about how probiotics might affect weight, including that they reduce fat absorption, but more research is needed.
There is currently no good quality evidence to show that taking a probiotic supplement will help with weight loss.
A recent analysis of studies that looked into probiotic supplements concluded that they don’t work for weight loss. But the authors note that more rigorous research is needed.
Most of the studies they looked at did not qualify as well-conducted clinical trials, which means the author did not include them in their analysis.
ZOE’s PREDICT1 study is a large clinical trial of over 1,000 people. Using the most advanced microbiome analysis tools, ZOE researchers have identified 15 “good” gut bugs that are linked to indicators of better health, along with specific foods that encourage them to thrive.
Good gut bacteria
The 15 “good” bugs that are associated with better health are linked with favorable metabolism, lower levels of dietary inflammation, lower blood pressure, and better blood sugar control.
People with more of these microbes also tend to have better blood fat control (lower levels of triglycerides and “bad” cholesterol), and less belly fat.
Some of these “good” microbes are also associated with a person having higher polyunsaturated fatty acids, such as omega-3 and omega-6.
Our bodies can’t make these fatty acids, so we have to get them from foods like seeds, nut oils, and olive oils, as well as oily fish.
15 “good” gut bugs identified by ZOE:
Freddy (Firmicutes bacterium CAG:95): associated with higher insulin sensitivity and lower levels of insulin.
Hannah (Haemophilus parainfluenzae): associated with higher insulin sensitivity and lower levels of insulin.
Oscar (Oscillibacter sp.57_20): associated with higher insulin sensitivity and lower levels of insulin.
Finn (Firmicutes bacterium CAG:170): associated with higher insulin sensitivity and decreased cardiovascular disease risk.
Rosie (Roseburia sp. CAG:182): associated with higher polyunsaturated fat levels and lower levels of insulin.
Claude (Clostridium sp. CAG:167): associated with higher insulin sensitivity and lower levels of insulin.
Otis (Oscillibacter sp. PC13): associated with higher polyunsaturated fat levels and lower levels of insulin.
Ellie (Eubacterium eligens): associated with higher polyunsaturated fat levels and lower levels of insulin.
Patrick (Prevotella copri): associated with higher insulin sensitivity and lower levels of insulin.
Veronica (Veillonella dispar): associated with higher insulin sensitivity and lower inflammation levels.
Felicia (Faecalibacterium prausnitzii): associated with higher polyunsaturated fat levels and lower levels of insulin.
Valentina (Veillonella infantium): associated with higher polyunsaturated fat levels and lower inflammation levels.
Billy (Bifidobacterium animalis): associated with higher insulin sensitivity and lower levels of insulin.
Rumi (Romboutsia ilealis): associated with higher polyunsaturated fat levels and lower inflammation levels.
Violet (Veillonella atypica): associated with higher insulin sensitivity and lower insulin levels after you eat.
Microbes compete with each other in the gut for resources. So, if you boost your “good” bugs, you will likely reduce the number of “bad” bugs in your gut.
People with obesity who have a less diverse gut microbiome tend to gain weight more easily than people with obesity who have a more diverse gut microbiome that is rich in beneficial microbes.
Probiotic foods contain trillions of microbes. Eating them can help to increase the diversity in your gut and create an environment where these “good” bugs will thrive, pushing out the “bad” bugs.
Skip pills, eat food
Most of the probiotic products available on the market today contain microbes selected because they are easy to grow. But at ZOE, we don’t focus on single microbes, we believe that boosting all 15 “good” gut bugs is important for health.
That’s why it’s important to understand your own microbes and how you can change them. With the ZOE program, you can learn about your personalized “gut boosters” — foods that promote the good bugs in your own gut.
Probiotic foods include fermented foods like kimchi, kefir, kombucha, sauerkraut, miso, and tempeh (made from soybeans).
You don’t have to include these fancy fermented foods to introduce more microbes into your diet, though. Even plain yogurt contains strains of live bacteria.
In fact, the TwinsUK study conducted by ZOE scientists found that eating yogurt is associated with changes in the composition of the gut microbiome and reduced belly fat.
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Certain cheeses are also probiotics, such as aged cheddar, parmesan, Swiss cheeses like gouda, and cottage cheese with live cultures.
Prebiotics are nutrients in food that we can't digest ourselves, such as fiber. Some of the most common prebiotic foods are onions, garlic, leeks, asparagus, legumes, and whole grains.
Eating more plant-based foods is a great way to introduce extra prebiotics into your diet, to allow the “good” gut microbes to thrive.
You should aim for 30 different plants a week (but remember, that can include nuts, seeds, and all the different vegetables you eat).
Gut bugs are personal
If you want to learn more about the microbes in your gut, join the ZOE program, which includes the most advanced gut microbiome test in the world.
We use the latest microbiome analysis to tell you exactly which bacteria call your gut home, and we provide you with personalized recommendations for foods that support optimal gut health.
Unpublished research from the ZOE team shows that closely following our personalized nutrition program led to an average weight loss of 9.4 pounds after 3 months. And around 80% of participants didn’t feel hungry and had more energy after their meals.
There are links between our gut microbiome and our weight. People who carry extra weight have different gut bacteria to those who do not.
Additionally, the “bad” bacteria identified in ZOE’s PREDICT study are associated with increased amounts of belly fat.
There’s little evidence to suggest that taking the probiotic supplements currently available on the market can help with weight loss, but eating probiotic foods such as yogurt is linked to changes in our microbiomes and less belly fat.
Having more of the “good” gut bugs identified by ZOE is also linked to reduced fat around the stomach, as well as a number of other measures of good health.
A more diverse gut microbiome is likely to include more of the “good” gut bugs associated with better health and weight loss.
Eating probiotic foods can increase the diversity in your gut, while consuming prebiotics — such as plants that are high in fiber — can encourage these good microbes to stick around.
Take a free quiz to find out how you can learn which foods are best for your body and your microbiome.
A core gut microbiome in obese and lean twins. Nature. (2008).
An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients. (2016).
Cultured gut microbiota from twins discordant for obesity modulate adiposity and metabolic phenotypes in mice. Science. (2013).
Lactobacillus gasseri SBT2055 suppresses fatty acid release through enlargement of fat emulsion size in vitro and promotes fecal fat excretion in healthy Japanese subjects. Lipids in Health and Disease. (2015).
Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individuals. Nature Medicine. (2021).
Prebiotics: Definition, types, sources, mechanisms, and clinical Applications. Foods. (2019).
Probiotics for weight loss: a systematic review and meta-analysis. Nutrition Research. (2015).
The gut-brain axis, the human gut microbiota and their integration in the development of obesity. Frontiers in Physiology. (2018).
Yoghurt consumption is associated with transient changes in the composition of the human gut microbiome. Preprint. (2020).