Worried about your BMI? This new method is MORE accurate at identifying obesity

BMI is based on the healthy weight for a person’s height, but experts have long pointed out its limitations.

However, a new study may have discovered a better method.

Researchers at Leeds Beckett University found that calculating a person’s waist-to-height ratio (WHtR) is more accurate and efficient.

It could be used, in particular, to identify whether someone is obese, and therefore at risk of several other health problems.

This new method examines whole-body fat percentage and visceral adipose tissue mass – the fat stored around the abdominal region where most of the internal organs are.

Worryingly, they also discovered that 36.5 per cent more adults would be classified as obese if this was used instead of BMI.

Dr Michelle Swainson, Senior Lecturer in Exercise Physiology in the Carnegie School of Sport at Leeds Beckett, said: “The conventional measurement of obesity used by GPs is BMI. Although there are benefits to this method, there is concern that a lot of people are being classified as obese by BMI when they are not or are being missed by this classification when they need to be referred for help.

“This is most definitely the case when people have a ’normal’ BMI but high abdominal fat is often dismissed. Whole-body fat percentage, and specifically VAT mass, are associated with health conditions including insulin resistance, type 2 diabetes and cardiovascular disease, but are not fully accounted for through BMI evaluation.”

Indeed, where you carry your fat can be very important.

Swainson said: “Carrying fat around the abdominal area has been shown to be an independent predictor of all-cause mortality in men and women. 

“Put simply, it is more important, especially for cardio-metabolic conditions, that your belt notch goes down than the reading on the scales.”

This new method – which involves waist circumference divided by height measurement – is not a new way to classify obesity, but it still isn’t being widely used in clinical settings.

In the study, BMI was weak as a predictor of whole-body fat percentage in both men and women.

Similarly, waist-to-hip ratio was a poor indicator of obesity.

Swainson added: “In current clinical practice, it is common to calculate BMI for an indication of whole-body fat and waist circumference for abdominal obesity.

“Our research has shown that WHtR is a more accurate alternative to these two measures and also a more time-efficient measure. By introducing this alternative, and more accurate, measure into clinical settings, more men and women would potentially be referred to programmes, such as weight management, to receive help in improving their health. 

“We have also shown how these simple measurements may be used as surrogates by GPs and other health care professionals when DXA scans are unavailable or inaccessible.”