# Body mass index cannot tell us whether we are healthy. Here’s what we should use instead

We have known for some time that body mass index (BMI) is an inaccurate measure for assessing a person’s weight and related health.

But it is still the tool of choice for doctors, population researchers and personal trainers.

Why is such an imperfect tool still used and what should we use instead?

First: What is BMI?

BMI is an internationally recognized screening method for classifying people into one of four weight categories: underweight (BMI less than 18.5), normal weight (18.5 to 24.9), overweight (25.0 to 29.9), or Obesity (30 or more).

This is a value that is calculated from a person’s mass (weight) divided by the square of their height.

Who invented BMI?

In 1832, Belgian mathematician Lambert Adolphe Jacques Quetelet (1796-1874) developed BMI as a mathematical model to represent the physical characteristics of an average Western European man.

It was originally called the Quetelet Index and was never intended as a medical assessment tool. The Quetelex index was renamed the “Body Mass Index” in 1972.

WhatIs the BMI incorrect?

It is simply not possible to use a mathematical formula to provide a complete picture of a person’s health.

BMI does not measure excess body fat, just “overweight”.

It does not distinguish between excess body fat or bone mass or muscle, and does not interpret fat distribution (which is an indicator of health, including type 2 diabetes, metabolic disorders and heart disease).

It also cannot detect the difference between social variables such as gender, age and ethnicity.

Because Quetelet’s formula only used Western European men, the results are not applicable to many other groups, including non-European ethnicities, postmenopausal women, and pregnant women.

The medical profession’s overreliance on BMI can be detrimental to patient health because it ignores much of what makes us healthy and focuses only on mass.

Rather than viewing BMI as a primary diagnostic test for determining a person’s health, it should be used in conjunction with other measurements and considerations.

Because researchers know that belly fat around our vital organs poses the greatest health risk, waist circumference, waist-to-hip ratio, or waist-to-height ratio provide more accurate measurements of health.

Waist circumference: is an effective measure of fat distribution, especially for athletes who have less fat and more muscle. When combined with BMI, it is most useful as a predictor of health.

For optimal health, waist circumference should be less than 94 cm for men and 80 cm for women, measured halfway between the bottom of your ribs and your hip bones.

Waist to Hip Ratio: Calculates the percentage of your body fat and how much is stored in your waist, hips and buttocks.

This is the waist circumference divided by the hip circumference. According to the World Health Organization, it should be 0.85 or less in women and 0.9 or less in men to reduce health risks.

It is particularly useful in predicting health outcomes in older people because the aging process changes the body proportions on which BMI is based. This is because as we age, fat mass increases and muscle mass decreases.

Waist to Height Ratio: Height divided by waist circumference. It is recommended to keep a person’s waist circumference less than half their height.

Some studies have found this measure to be most highly correlated with health predictions.

Body composition and body fat percentage can also be calculated through skinfold measurements by assessing specific locations on the body (e.g., abdomen, triceps, or quadriceps) with a skin caliper.

These more formal tests may be combined with a review of lifestyle, diet, physical activity, and family history.

What makes us healthy besides weight?

A diet containing whole grains, low-fat protein sources such as fish and legumes, eggs, yoghurt, cheese, milk, nuts, seeds and plenty of fresh fruit and vegetables reduces our risk of cardiovascular disease.

Limiting processed foods and sugary snacks, as well as saturated and trans fats, can help us manage weight and ward off diet-related illnesses.

Being physically active most days of the week improves overall health. This includes two strength training sessions per week and 2.5 to five hours of moderate cardio activity or 1.25 to 2.5 hours of vigorous cardio activity.

Weight is just one aspect of health and there are far better measurements than BMI.

Written by Rachael Jefferson-Buchanan. The conversation.

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