Increased body mass index (BMI) – a measure of weight accounting for a person’s height—has been shown to be a likely causal contributor to mortality.
This is the finding of a new study led by the University of Bristol.
The researchers used measurements and mortality data from 500,000 people.
Specifically, the study shows that for those in UK Biobank (a study of middle to late aged volunteers), every 5kg/m2 increase in BMI was linked to an increase of 16% in the chance of death and 61% for those related to cardiovascular diseases.
It is already known that severe obesity increases the relative risk of death.
But previous studies have produced conflicting results with some appearing to suggest a protective effect at different parts of the spectrum of body mass index.
Until now, no study has used a genetic-based approach to explore this link.
In the study, the Bristol team applied a method called Mendelian randomization.
It is a technique that uses genetic variation in a person’s DNA to help understand the causal relationships between risk factors and health outcomes—here mortality.
This method can provide a more accurate estimate of the effect of body mass index on mortality by removing confounding factors.
Using data from the UK Biobank, the team were able to show that the apparent optimum body mass index for survival was within the normal weight rather than overweight range found with observational studies.
In addition, the association remained flattered over a larger range of body mass index.
The findings link body mass index and mortality and confirm that being overweight increases a person’s risk of death from all causes including cardiovascular diseases and various cancers.
The researchers suggest that the findings highlight the need for a global effort to reduce the surging levels of obesity within society.
It also suggests that in most cases, any reduction in body mass index to a normal, healthy level is likely to be beneficial.
Dr. Kaitlin Wade is the lead author of the study.
The work is published in Obesity Editors’ Choice.
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