Waist circumference is ‘vital sign’ of health and should be measured alongside BMI, experts say

Waist circumference could be as important as body mass index (BMI) in terms of managing people’s health and lowering the risk of obesity-related illness, a new statement has suggested.

The consensus statement, published in the journal Nature Reviews Endocrinology, looked at existing evidence that BMI is not enough to assess the associated heart and other health risks of obesity on its own.

Robert Ross of Canada's Queen's University Lifestyle and Cardiometabolic Research Unit and 16 fellow experts are now calling on healthcare professionals to routinely measure the waists of their patients, as they believe this could help with protecting and managing their health.

Current guidelines state that doctors only need to take patients’ BMI into consideration when assessing the risk of obesity-related health issues.

But researchers believe more attention should be paid to the excess body weight stored around the middle of the body, known as central fat.

BMI is defined as a person’s total mass divided by the square of their height.

In the UK, a score of 18.5 to 24.9 is considered healthy, 25 to 29.9 overweight, and 30 and above obese.

However, the score does not take into account the type or location of fat, which researchers can play a role in the risk of developing serious illnesses such as heart disease or cancer.

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Decades of research suggests that combining the measures of BMI and waist circumference could paint a clearer picture of the health risks a person might face due to their weight, statement authors said.

“The failure of BMI to detect such an increase in abdominal obesity confirms the limitations of BMI alone to identify the phenotype of obesity that conveys the greatest health risk,” the authors of the statement wrote.

The experts cited several studies showing waist circumference has risen over the past few decades and that it was the strongest predictor of visceral fat (the fat stored inside the abdominal cavity and around several vital organs), which poses the most significant health risk.

They said exercising regularly at a moderate intensity and/or changing diet can shrink the waistline and that measuring waist would help to see if those measures are working.

The researchers are now calling for further research but hope their findings might lead waist circumference to be considered as part of standard clinical measurements.

“The main recommendation of this consensus statement is that waist circumference should be routinely measured in clinical practice, as it can provide additional information for guiding patient management,” the statement concludes.

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Last July, further research revealed waist size could offer a better indication of a woman’s overall health and risk of obesity-related illness than BMI.

The study, by a team at the University of Iowa and published in the Journal of the American Medical Association, tracked the health of more than 156,000 post-menopausal women between the ages of 50 and 79 from 1993 to 2017.

They found that those with a BMI reading of less than 25 but a waist circumference of 35 inches or greater were at a 31 per cent higher risk of dying during the study period than women of a normal weigh and a waist of less than 35 inches.

Commenting on the findings Wei Bao, professor of epidemiology in the UI College of Public Health and the study’s lead author, said: “The results suggest we should encourage physicians to look not only at body weight but also body shape when assessing a patient’s health risks.

Last year it was revealed that obesity has overtaken smoking as a risk factor for some types of cancer – including four of the most common.

In cases of bowel, kidney, ovarian and liver cancer, obesity is a bigger risk factor than cigarettes, according to the latest research from Cancer Research UK.

Obesity is thought to affect around one in every four adults in the UK, and roughly one in five children aged 10 to 11.

Last year, a debate broke out over whether obesity should be labelled as a disease or a lifestyle choice, after the Royal College of Physicians called for obesity to be reclassified as a the latter.