High and low BMI both linked to high mortality - Lancet

U.K: Body mass index(BMI) proves to be an important biomarker associated with increased mortality risk.

A new of its kind study published in the journal The Lancet suggests that a Body Mass Index (BMI) between 21-25kg/m2 is associated with the lowest risk of dying from cancer and heart disease.

The study revealed that Body Mass Index had J-shaped associations with overall mortality and most specific causes of death; for mental and behavioral, neurological, and external causes, lower Body Mass Index was associated with increased mortality risk.

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Krishnan Bhaskaran and his associates conducted a UK population-based cohort study of 3 632 674 people to study the association of BMI on different causes of death.

The key analysis is as follows:

• Body Mass Index has a J-shaped association with overall mortality; the estimated hazard ratio per 5 kg/m2increase in Body Mass Index was 0·81 below 25 kg/m2 and 1·21 above this point.


• Body Mass Index was associated with all-cause of death categories except for transport-related accidents, but the shape of the association varied.


• Most cases, including cancer, cardiovascular diseases, and respiratory diseases, had a J-shaped association with BMI, with lowest risk occurring in the range 21–25 kg/m2.


• For mental and behavioral, neurological, and accidental (non-transport-related) causes, Body Mass Index was inversely associated with mortality up to 24–27 kg/m2, with little association at higher BMIs


• For deaths from self-harm or interpersonal violence, an inverse linear association was observed.


• Associations between Body Mass Index and mortality were stronger at younger ages than at older ages, and the Body Mass Index associated with the lowest mortality risk was higher in older individuals than in younger individuals.


• Compared with individuals of healthy weight (BMI 18·5–24·9 kg/m2), life expectancy from age 40 years was 4·2 years shorter in obese (BMI ≥30·0 kg/m2) men and 3·5 years shorter in obese women, and 4·3 years shorter in underweight (BMI <18·5 kg/m2) men and 4·5 years shorter in underweight women.


• When smokers were included in analyses, results for most causes of death were broadly similar, although marginally stronger associations were seen among people with lower Body Mass Index, suggesting slight residual confounding by smoking.

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“We found important associations between Body Mass Index 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 21-25kg/m2 is linked to the lowest risk of dying from most diseases," said Bhaskaran.

For full information log on to https://doi.org/10.1016/S2213-8587(18)30288-2