Does gut health affect weight?

How does your unique 'microbiome' – the trillions of tiny bacteria in your gut – affect your weight, and do home testing kits work? We asked a dietitian to explain.

A woman standing on weighing scales

Exciting research has recently been carried out into the function of gut bacteria, and its impact on your overall health and wellbeing. Some fascinating studies have suggested a link between gut health and weight. We asked dietitian Emer Delaney to explain the science, plus give us her top tips to improve gut health along with her opinion on home microbiome testing kits.

What is the 'gut microbiota' and why is it important?

The gut microbiota is a complex system made up of the bacteria in the gut, viruses and other microbes that have colonised the gastrointestinal tract. The two terms microbiota and microbiome are often used to mean the same thing. With the global increasing obesity epidemic, scientists are starting to look at the possible relationship of gut microbiota and obesity and how dietary modifications may help. They are only now beginning to understand the role the microbiota play in health, including obesity.

How does gut health and the microbiome affect an individual’s weight?

The link between the microbiome and weight is a fast developing field. Researches found in animal studies that transplanting the gut bacteria of obese mice into lean mice caused the lean mice to gain fat cells rapidly. While these studies can’t be directly correlated to humans, they are the building blocks to further research.

More recently, researchers have found significant differences in the gut bacteria of lean and obese individuals and twins. Those who were obese had different gut bacteria than their non-obese twins, and obesity was associated with lower gut bacteria diversity. The reason for this is still not fully understood, however work continues in this exciting field.

Scientists are looking at gut flora to see if they can draw links with weight and develop uses in therapy treatments, such as by altering appetite. A French research team concluded that gut bacteria may help control when and how much we eat. They found that gut microbes produce the hormones involved in appetite regulation 20 minutes after being given nutrients. Giving these appetite hormones to mice resulting in the mice eating less food. However, more research in this field is needed before we can begin to apply it to humans. In the meantime, eating a diet rich in plant-based foods such as whole grains, fruit and vegetables and low in unhealthy saturated fat can change gut microbiota.

A selection of fruit and vegetables

What can we do to improve our gut microbiome?

Eating a diet rich in fibre from fruit, vegetables, whole grains, beans and pulses and low in saturated fat can help. While the body cannot digest all fibre, certain bacteria in the gut can – and this stimulates their growth. One study found that a diet high in fruit and vegetables prevented the growth of some bacteria that have been linked to cardiovascular disease. Other studies have concluded that apples, Jerusalem artichokes and almonds and pistachios increased the beneficial Bifidobacteria, which help prevent intestinal inflammation and enhance gut health.

Do home microbiome test kits work?

Home microbiome test kits promise to help you understand the makeup of your unique gut bacteria by sending off a stool sample to be analysed in a laboratory. They are becoming very popular due to the increased interest in the gut microbiome, however there is no standard testing method and no quality control. It is important to remember that gut microbes change regularly in response to diet, sleep, stress, travel and exercise. As a result, you could receive different results on different days due to these variables. Kits say they can provide a snapshot of the “core” microbes, however these may still change due to the factors mentioned above. To really see how lifestyle affects the gut, people would need to take a test almost daily.

When should you see a specialist?

If you are concerned about your digestive health, I would recommend speaking to your GP – especially if you have been feeling unwell for a prolonged period of time. There are also the ‘red flags’ that means immediate actions should be sought. These include blood in stool or urine, unintentional weight loss, persistent vomiting or iron deficient anaemia.

Microbes & me

Our new series, in collaboration with BBC Future, looks at all the factors that affect our unique microbiomes – from dietary choices to lifestyle factors.

We’ve worked with dietitian Emer Delaney to bring you expert information and specially selected recipes that will help you to understand how to eat for better digestive health.

Find out more...

Could gut bacteria microbes make you fat?
How does diet affect gut health?
What are probiotics and what do they do?
Gut-friendly vegan recipes
Visit our Microbes & Me series hub page


This article was published on 23rd January 2019.

Emer Delaney BSc (Hons), RD has an honours degree in Human Nutrition and Dietetics from the University of Ulster. She has worked as a dietitian in some of London's top teaching hospitals and is currently based in Chelsea.

All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

Comments, questions and tips

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avaflava's picture
avaflava
6th Feb, 2019
This is such an interesting and important topic! Everyone should be aware of this, thanks for sharing!
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