Having This BMI Will Protect Against Cancer And Heart Disease Deaths

Body Mass Index, or BMI, is a measure of a person's weight in relation to their height. Getty Images

Scientists believe a person's body mass index (BMI) could predict their risk of dying from cancer and heart disease, as well as the number of years their weight may shave off their life.

BMI is a measure of whether a person's weight is healthy. It is calculated by dividing an adult's weight in kilograms by their height in meters squared. The resulting figure corresponds to the BMI scale, with 18.5 to 24.9 considered to be an ideal range.

The study published in The Lancet Diabetes and Endocrinology linked both a low and a high BMI to a higher risk of death.

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Read more: Why being skinny fat could be just as dangerous as being obese

Those with a BMI between 21 to 25 had the lowest risk of dying of cancer or heart disease. But men deemed obese, with a BMI of 30 or above, were at risk of losing 4.2 years of their lives on average, while the figure was 3.5 years for women. An obese BMI was linked to a range of disease including cancer, heart disease, and conditions such as liver disease, diabetes, and respiratory illness.

Conditions including dementia, Alzheimer's, heart and respiratory diseases, as well as suicide were meanwhile linked to being underweight.

For every 5kg/m2 a person scored above 25 on the scale, their risk of heart disease rose by 29 percent from the baseline. And every 5kg/m2 below a BMI of 21 was associated with a 13 percent higher chance of developing the condition.

In what is one of the largest ever studies investigating whether BMI can predict a person's risk of dying, researchers assessed anonymized data on 3.6 million people from the U.K. Clinical Practice Research Datalink (CPRD). The dataset included BMI, which was assessed alongside data from official figures in the U.K. on causes of death.

Krishnan Bhaskaran, lead author of the study and Associate Professor in Statistical Epidemiology at the London School of Hygiene & Tropical Medicine, told Newsweek: "The most striking thing about our findings was how widely BMI was linked to different causes of death. BMI was associated with deaths from nearly all major causes."

While BMI is a useful indicator of whether a person is a healthy weight, Bhaskaran acknowledged it is "not a perfect measure. For example athletes may be very fit but have a high BMI, but the vast majority of the time, a high BMI is due to excess fat, and being very easily measured, BMI is still a useful tool to help people understand whether they are at a healthy weight."

However, he maintained that for the average person, the research reinforces the importance of maintaining a healthy body weight, with BMIs of 21-25kg/m2 being associated with the lowest risk of most diseases.

"The evidence shows that, for people wishing to lose weight, a slow and steady approach is best—making realistic and permanent changes to your diet and levels of physical activity that will be sustainable in the long term."

Earlier in October, the authors of a separate study published in the journal Cell Metabolism devised a new way to estimate if a person's weigh is potentially harmful to their health.

They argued calculating the metabolome could be a more accurate measure of health than BMI. The metabolome is a product of how a living thing's genome interacts with its environment, comprised of a number of small molecules known as metabolites—like glucose.