There are calls for the Body Mass Index measurement, BMI for short, to be scrapped.

Proponents for its abandonment argue that it is at best a poor predictor of overall health and wellbeing, while at worst may lead to poor body image, reduced self-esteem and the development of eating disorders.

They advise doctors and anyone involved in healthcare should adopt a “health at every size approach”, to allow all individuals to access services irrespective of their BMI. At points, a significantly raised BMI has been a bar to certain elective procedures, due to data showing poorer outcomes and greater risk of complications. Conversely, patients above a certain BMI have been unable to rapidly access eating disorder services, their condition being not deemed severe enough to warrant urgent intervention.

The pandemic has seen a significant rise in mental health presentations, with a three-fold increase in referrals to eating disorders services.

Body Mass Index is weight in kg divided by height in metres squared. Invented in 1830 by Belgian astronomer and mathematician Lambert Quetelet, it has been adopted by the medical community for over 100 years. A BMI of under 18.5 is underweight, between 18.5 to 24.99 “normal”, 25 to 29.99 classified as overweight, with 30 and above falling into the obese category. Obesity is further sub divided into mild, moderate and severe at BMIs of 30,35 and 40 respectively. Several online calculators exist. That provided by the NHS website is more sophisticated as it asks other questions also very relevant to health including ethnic origin and levels of physical activity.

The question remains; how useful is BMI on its own as a marker of absolute health? The likely answer is that it is too basic to be used in isolation. Consider that at the height of his career, legendary bodybuilder Arnold Schwarzenegger had a BMI of 31, landing him in the obese category, yet his percentage body fat was incredibly low.

Other tools are available that provide an equally useful insight into our health, risk of disease and longevity. Percentage body fat is most simply measured with callipers at various points on the body. A figure of 2-4% for men is seen as healthy, with numbers over 25% linked to increased likelihood of non-communicable diseases, these being heart disease, stroke and diabetes to name a few. For women ideal levels are 10-13%, with anything over 32% being cause for concern.

Where your fat is distributed also matters. That over the hips and thighs is associated with less risk than if centred over the abdomen, a reflection of the amount of fat contained in the abdomen and around the intra-abdominal organs. If located here it can adversely affect their function, leading to fatty liver disease, diabetes and heart disease.

Measurement of waist to height ratio is another predictive tool, with data showing your waist circumference should be less than half your standing height for better health.

Oxford mathematician Professor Nick Tefethen argued in 2013 that the BMI calculator was too simplistic and that it made shorter people appear thinner than they were, and taller people fatter than in reality.

Significant studies have shown that four positive health behaviours are strongly linked with reduced levels of disease, better physical and mental health, as well as increased longevity. These are not smoking, alcohol in moderation (though there is no evidence that non-drinkers should start consuming alcohol), eating five or more portions of fruit and vegetables per day, and exercising twelve or more times a month. I imagine that none of this will come as a surprise.

In conclusion, my feelings are that the BMI measurement should not be scrapped. While it is only at the extremes of the scale that on its own it is a marker of greater health risks, nonetheless it is a useful tool to be used in conjunction with other measurements. As always, the trend is more important than any single number in isolation. Trends can be used to demonstrate treatment successes, for example weight loss, but also to highlight concerns at both ends of the scale. Being significantly underweight is as much of a health risk as suffering morbid obesity.

I feel more menus, including those in takeaways and restaurants, should contain calorie and nutritional information, to allow individuals to make fully informed decisions. Persons should never be fat shamed, but by the same token we should not celebrate the thigh gap, nor promote images of excess muscularity as ideals to aspire to.

Dr. Zak Uddin, General Practitioner