Study findings could pave the way for development of new strategies to prevent and treat obesity

Wednesday, 05 April 2023

New research has shown that weight loss, or bariatric, surgery can significantly alter the levels of bile acid associated with higher appetite, as can taking fibre supplements but to a lesser degree.

Bariatric surgery can be used as a treatment for people who are very obese and there are several types of surgery available, such as reducing the size of the stomach or rerouting the top part of the stomach to the small intestine. It’s an invasive procedure but can lead to significant improvements in weight loss, metabolic health, and a reduction in appetite – though the reasons for this are unknown. Bile acids are a marker of poor cardiometabolic health that can affect liver function and inflammation.

A study, published today in Cell Reports Medicine by researchers from the University of Nottingham, King’s College London and Amsterdam University Medical Centre, has shed light on the molecules underlying the benefits of this kind of surgery on patient appetite and metabolism.

Researchers studied a group of patients in Amsterdam who had undergone bariatric surgery by measuring levels of bile acids before surgery and a year post-operation. They also studied bile acids from two population studies – TwinsUK, run by King’s College London, and PREDICT, run by King’s College London and nutrition company ZOE.

The study found that a specific bile acid called isoursodeoxycholate (isoUDCA), which is associated with higher appetite and worse metabolic levels, decreased after bariatric surgery and after taking fibre supplements. Levels of isoUDCA did not decrease after consuming omega-3 supplements.

Joint lead author Professor Ana Valdes from the University of Nottingham’s School of Medicine said: “Bariatric surgery is not only extremely effective at helping people lose weight by reducing their appetite, but also improves their liver function and their metabolism."

Ana Valdes photo
What our study shows is that specific microbial metabolite is involved in some of these benefits and that, although to a more modest extent, dietary fibre might mimic some of these effects.
Professor Ana Valdes, the University of Nottingham’s School of Medicine

Professor Valdes continued: "This could help design dietary supplementation studies aimed at increasing satiety and improving liver parameters.”

By understanding these mechanisms, scientists may be able to develop new interventions that mimic the effects of bariatric surgery without putting patients through the procedure itself. Bariatric surgery is also only suitable for those who are severely obese, and understanding whether isoUDCA can be modified by lifestyle interventions could lead to more targeted treatments for obesity.

Joint lead author Dr Cristina Menni, from King’s College London, said: “The study's results have important implications for the development of targeted interventions for metabolic disorders focused on the gut microbiome."

By better understanding the complex interplay between genetics, the gut microbiome, and diet in regulating bile acid levels and their impact on appetite and metabolic health, we may be able to develop new strategies for preventing and treating obesity and metabolic syndrome.
Dr Cristina Menni, from King’s College London

Another key finding was seeing the strong influence of gut microbes on the levels of isoUDCA. This confirms that the gut microbiome is key to determining the outcomes of bariatric surgery and sheds light on the ways in which gut microbes modify a person's metabolism.

Co-author Professor Tim Spector, Professor of Genetic Epidemiology at King’s College London and co-founder of ZOE, the personalised nutrition company, said: “This study highlights the key role that fibre plays in appetite regulation and metabolism, harnessed by specific gut microbes. Advanced gut microbiome testing (as used by ZOE) provide personalised insights that can support metabolic health. The gut microbiome and its chemical products such as these bile acids hold huge promise for reducing obesity without the need for invasive surgery.”

Story credits

More information is available from Professor Ana Valdes at the University of Nottingham on, or; Danielle Hall, Media Relations Manager at the University of Nottingham, at or 0115 846 7156.     

About King’s College London

King's College London is one of the top 35 UK universities in the world and one of the top 10 in Europe (QS World University Rankings, 2020/21) and among the oldest in England. King's has more than 31,000 students (including more than 12,800 postgraduates) from some 150 countries worldwide, and some 8,500 staff.

King's has an outstanding reputation for world-class teaching and cutting-edge research. In the 2021 Research Excellence Framework (REF), King’s maintained its sixth position for ‘research power’ in the UK. King’s has also been rated third amongst multidisciplinary institutions for impact, with 67.8% of its research impact rated outstanding.

Danielle Hall - Media Relations Manager - Faculty of Engineering
Phone: 0115 846 7156

Notes to editors:

About the University of Nottingham

Ranked 32 in Europe and 16th in the UK by the QS World University Rankings: Europe 2024, the University of Nottingham is a founding member of the Russell Group of research-intensive universities. Studying at the University of Nottingham is a life-changing experience, and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement.

Nottingham was crowned Sports University of the Year by The Times and Sunday Times Good University Guide 2024 – the third time it has been given the honour since 2018 – and by the Daily Mail University Guide 2024.

The university is among the best universities in the UK for the strength of our research, positioned seventh for research power in the UK according to REF 2021. The birthplace of discoveries such as MRI and ibuprofen, our innovations transform lives and tackle global problems such as sustainable food supplies, ending modern slavery, developing greener transport, and reducing reliance on fossil fuels.

The university is a major employer and industry partner - locally and globally - and our graduates are the second most targeted by the UK's top employers, according to The Graduate Market in 2022 report by High Fliers Research.

We lead the Universities for Nottingham initiative, in partnership with Nottingham Trent University, a pioneering collaboration between the city’s two world-class institutions to improve levels of prosperity, opportunity, sustainability, health and wellbeing for residents in the city and region we are proud to call home.

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