For many people considering weight loss surgery, this question matters just as much as how much weight they might lose.
Living with obesity increases the risk of serious health conditions, including heart disease, type 2 diabetes, and certain cancers. Over time, these risks can affect how long someone lives. Bariatric surgery is well established for supporting long-term weight loss and improving health, but its impact on life expectancy has been less certain.
To explore this, researchers in Sweden conducted a long-term observational study of people with obesity over several decades.
This study is known as the SOS study. It was published in The New England Journal of Medicine and compared long-term survival in people with obesity who underwent bariatric surgery with those who received usual obesity care.
The SOS study explained
The SOS study is one of the longest and most detailed studies of bariatric surgery ever conducted. It recruited participants between September 1, 1987, and January 31, 2001, and followed people with severe obesity for up to 30 years, allowing researchers to examine long-term health outcomes over a much longer period than most previous research.
Participants were divided into three groups. In total, 2,007 people were included in the surgery group, 2,040 in the usual non-surgical obesity care group, and 1,135 people from the general population were included as a reference cohort for comparison.
All participants in the surgery and usual-care groups were aged between 37 and 60 at the start of the study and had severe obesity.
The types of surgery reflected standard practice at the time and included procedures designed to reduce food intake and support long-term weight loss. Since the SOS study began, bariatric surgery has continued to evolve, and newer surgical techniques are now used that were not available when the study started. Participants receiving usual care continued with conventional obesity treatment, such as lifestyle advice and medical management.
Importantly, information on deaths was available for almost every participant, making the long-term findings particularly reliable.
Results from the SOS study
Over the course of the study, researchers found clear differences between people who had bariatric surgery and those who received usual obesity care:
- People who underwent bariatric surgery were 23% less likely to die during the follow-up period.
- Deaths from cardiovascular disease and cancer were lower in the surgery group, with a 30% lower risk of death from cardiovascular disease and a 23% lower risk of death from cancer.
- When life expectancy was estimated, people who had bariatric surgery lived around three years longer on average than those who received usual care.
Compared with the general population, long-term health risks were not completely eliminated. This reflects the lasting effects of severe obesity earlier in life and highlights the importance of ongoing medical follow-up after surgery.
Understanding what these findings mean
In simple terms, the study shows that bariatric treatments can help people with severe obesity live longer than they would with usual care alone. A gain of around three years in life expectancy is considered meaningful when compared with many other medical treatments aimed at reducing long-term health risks.
The study also highlights the importance of care beyond surgery itself. Some risks, including mental health challenges and deaths related to alcohol misuse or trauma, were more common after weight loss surgery. This reinforces the need for long-term follow-up, psychological support and a holistic approach to obesity treatment.
How safe was surgery?
Short-term surgical risk in the study was low. Within 90 days of surgery, the death rate was 0.2%, and fewer than 3% of patients required repeat surgery during that period.
It’s also worth noting that surgical techniques and follow-up care have continued to improve since the SOS study began, and many of the procedures used at the time are no longer standard practice today.
Why this study matters
For people in the UK considering bariatric surgery, concerns about long-term safety and benefit are common. The SOS study provides rare, long-term evidence showing that bariatric surgery is associated not only with improved health but also with longer life expectancy compared with usual obesity care.
Rather than restoring life expectancy to that of the general population, bariatric surgery appears to reduce the gap, helping people with obesity live longer and healthier lives than they otherwise might.
If you’re exploring treatment options for obesity, the specialist bariatric team at Phoenix Health can help you understand whether bariatric surgery or other approaches may be suitable for you, based on your individual health needs.
Bariatric surgery is not suitable for everyone. At Phoenix Health, all bariatric treatment decisions are made following a full clinical assessment and a detailed discussion of potential risks, benefits, and long-term aftercare, ensuring each patient is supported in making an informed decision.
References:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7580786/
Medically Reviewed by Mr. Qutayba Almerie, MD, MSc, FRCS
Consultant Upper GI & Bariatric Surgeon, Medical Director at Phoenix Health.
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