NUTRITION

Here’s Why BMI is a Flawed Indicator of Health

BMI, or body mass index, has long been the medical standard for measuring health worldwide. But does it tell us the whole story about our health? What could we use instead? A nutritionist tells us.

By Shreya Maji
08 March 2022

The term BMI (body mass index) was first coined in 1972 by American researcher Ancel Keys, who revived an old scale of measurement from the early 19th century to analyse body weight in terms of height in 7,400 European men. The body mass index is a person’s weight in kilograms divided by their height in metres squared. By 1998, the United States and subsequently the whole world had officially started using this scale to define obesity—having a BMI between 18.5 and 25 was considered healthy or “normal”, while any number below or above that range was called underweight and overweight respectively.

 

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“BMI is generally considered a reliable way to determine whether a person has too much body fat,” says Kripa Jalan, Sports Nutrition Specialist and founder of Burgers to Beasts, a holistic nutrition centre. “It accounts for the fact that taller people have more tissue than shorter individuals and so tend to weigh more. It's an easy way for clinicians to screen who might be at greater risk of health problems due to their weight. ” This is because people who are overweight or obese according to this standard are more at risk of chronic diseases like high blood pressure, cardiovascular diseases and type 2 diabetes, says scientific research. But in recent years, BMI has increasingly come under scrutiny from researchers as a flawed standard of health.

 

Why is BMI an Inaccurate Measure of Health?

 

BMI can provide us with a basic tool for assessment of disease risk, but it gives us an incomplete picture of our health. “BMI is not a perfect measure, since it does not directly assess body fat,” says Kripa. “Muscle and bone are denser than fat, so a muscular person may have a high BMI, yet not have too much fat.” As an example, she cites the fact that the BMI would put a 6 foot tall, 90 kg male athlete in the same category as a 6 foot tall 90 kg overweight individual with poor lifestyle habits. “Visually and metabolically, we know that they’re dissimilar,” she points out.

 

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In a letter to The Economist, Nick Trefethen, Professor of Numerical Analysis at Oxford University’s Mathematical Institute pointed out that the BMI measurement divides the weight by a relatively greater number in short people and a lesser number in taller people, making the taller individuals think that they are fatter than they actually are. BMI also does not take into account abdominal or visceral fat, something which particularly affects Asian countries. Abdominal fat, according to a 2017 study published in Obesity and Lipotoxicity, poses a greater health risk than body fat distributed elsewhere. BMI is also not the correct standard for pregnant or nursing women, who typically have a higher body weight, which usually does not pose any long-term health risk for them. Moreover, BMI was standardised by testing it on the European white population, and it leaves out any ethnic and racial differences in body types and body composition.

 

Lifestyle factors, such as exercise, diet, smoking and stress levels, which greatly affect your risk of chronic diseases, are also left out by BMI. “In reality, size is not always a direct reflection of health,” says Kripa. “Weight bias often goes unnoticed due to cultural values of thinness. Thin is viewed as healthy and ‘fat’ is viewed as unhealthy. There are many ‘thin’ individuals who are aerobically unfit and eat a nutrient-poor diet and many ‘fat’ individuals who are aerobically fit and eat a nutrient-rich diet,”she adds.

 

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What Can We Use Instead of BMI?

“I’d say body fat percentage is a far better marker of determining body composition,” Kripa tells us. “On the health front, your blood never lies—so, having vital markers checked under the care of a practitioner could be a good way to measure progress. Lastly, one could also go by their energy levels, performance, cognition and menstrual dashboard indicators.”

 

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A healthy weight is hard to standardise across the global population. Regular measurements of blood cholesterol, triglycerides, blood pressure and blood sugar can give you a much more complete picture of your health. If you are still concerned about your BMI, consulting your general physician or a nutritionist will give you a better idea of what is healthy for your own body.

 

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