This meta-analysis of 16 matched cohort studies and one prospective controlled trial, involving 174 772 participants with severe obesity during 1.2 million patient-years of follow up, demonstrated that surgery is associated with a 49.2% reduction in all-cause mortality compared to usual medical obesity care. Median life expectancy was 6.1 years longer across the whole group who underwent metabolic–bariatric surgery compared to those receiving medical treatment. For those with severe obesity and diabetes at baseline, median life expectancy was 9.3 years longer in the surgical group versus the usual treatment group, compared to 5.1 years’ life expectancy gain with surgery versus medical treatment in those without diabetes. The numbers needed to treat to prevent one additional death over a 10-year time frame was 29.8 for those without diabetes and only 8.4 for those with diabetes.
In this meta-analysis, survival benefit did not differ between those undergoing sleeve gastrectomy, gastric banding or gastric bypass surgery, although the authors cautioned that the comparative effects of the different procedures on long-term survival is not yet resolved due to limitations with their study. People undergoing bariatric surgery are usually in the 40–50-year age group, so mortality rates in the individual studies are low – 5.3–10.7 deaths per 1000 person-years – hence the usefulness of this meta-analysis.
Uptake of metabolic–bariatric surgery remains low globally – less than 1% of eligible individuals, based on weight. The authors calculated that the potential benefits of increasing that rate by 1% amongst those who are eligible for surgery could yield between 5.1 million and 6.6 million life-years in those with and without type 2 diabetes, respectively (Syn et al, 2021).
Lifestyle measures remain important, and it is likely those receiving bariatric surgery would also have had lifestyle guidance and may have had drug therapy as well. More effective drug treatments for obesity (high-dose liraglutide and semaglutide, phentermine/topiramate, and naltrexone/bupropion) and type 2 diabetes glucose-lowering therapies that can reduce cardiovascular mortality rates may attenuate the differences between medical and surgical management of severe obesity in the future.
Around 35% of adults in the UK are obese. Writing in an accompanying comment in the same issue of The Lancet, Mingrone and Bornstein (2021) highlight the obesity-related reductions in life expectancy found in a previous UK population-based cohort study of 3.6 million individuals (Bhaskaran et al, 2018). Male non-smokers had reductions of 5.9 and 9.1 years with class I or class II obesity, respectively, with reductions of 4.2 years and 7.7 years in females with class I or class II obesity. This is negatively impacted by coexisting diabetes, with a 40-year-old male with obesity and diabetes likely to lose 11.6 years of life and a 40-year-old woman likely to lose 14.3 years. Additional unknowns are whether duration of obesity impacts life expectancy and whether prevention or early intervention to manage obesity can help avoid organ damage.
The authors concluded that this meta-analysis “adds to a growing evidence base supporting a role for metabolic–bariatric surgery in the management of obesity, especially in those with type 2 diabetes.” As bariatric surgery services restart across the UK, it is important we know the pathway to access surgery in our area, and remember to discuss surgery, where appropriate, with people with severe obesity with and without type 2 diabetes.