A patient’s BMI is linked to risk of death from every major cause – except transport accidents, a new study has claimed.
Researchers from the London School of Hygiene and Tropical Medicine (LSHTM) analysed over 3.6m patient records and found that both low and high BMI were associated with an increased risk of death.
The study, published in The Lancet Diabetes and Endocrinology, set out to assess the associations between BMI and a range of cause-specific mortality outcomes, including cardiovascular and respiratory conditions, and cancers.
It found that excess weight was associated with a higher risk of deaths in nearly every major category, while low body weight was associated with deaths from every category except for liver cirrhosis.
The paper said: ‘We observed a J-shaped association between BMI and all-cause mortality, with lowest mortality at 25 kg/m2. BMI was associated with mortality risk from every main category of cause except for transport-related accidents.’
It added: ‘Compared with individuals of healthy weight, life expectancy from age 40 years was 4.2 years shorter in obese men and 3.5 years shorter in obese women, and 4.3 years shorter in underweight men and 4.5 years shorter in underweight women.’
Lead author and associate professor in statistical epidemiology at LSHTM Krishnan Bhaskaran explained that while it is known that BMI is ‘linked to the risk of dying overall’, there was ‘surprisingly little research’ on deaths from specific causes.
She said: ‘We have filled this knowledge gap to help researchers, patients and doctors better understand how underweight and excess weight might be associated with diseases such as cancer, respiratory disease and liver disease.
‘We found important associations between BMI and most causes of death examined, highlighting that body weight relative to height is linked to risk of a very wide range of conditions. Our work underlines that maintaining a BMI in the range 21-25 kg/m2 is linked to the lowest risk of dying from most diseases.’
This comes after Public Health England said that GPs should measure and record patients’ BMI routinely, as part its strategy to cut adult obesity rates.