Harrison S, Dixon P, Jones HE, et al. - Mendelian randomisation, which is less biased than existing observational methods, can be used to estimate the impact of interventions on quality of life and healthcare costs. Body mass index (BMI) interventions are likely to be cost-effective, possibly more so than previously predicted using simulation methods that limit the effect of BMI changes on health conditions to cancer, cardiovascular disease, cerebrovascular disease, and type 2 diabetes.

• A total of 310,913 unrelated white British participants from England and Wales were included in the analysis.

• A unit increase in BMI reduced QALYs by 0.65% of a QALY per year and increased annual total healthcare costs by £42.23 per person.

• The authors estimated that a unit increase in BMI decreased QALYs by only 0.16% of a QALY per year when only health conditions commonly considered in the previous cost-effectiveness modelling studies (cancer, cardiovascular disease, cerebrovascular disease, and type 2 diabetes).

• They estimated that both laparoscopic bariatric surgery among people with BMI greater than 35 kg/m ², and restricting volume promotions for high fat, salt, and sugar products, would increase QALYs and lessen total healthcare costs, with net monetary benefits (at £20,000 per QALY) of £13,936 per person over 20 years, and £546 million in total per year, respectively.