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For decades, body mass index (BMI) has been the most widely used method to determine whether someone is a healthy weight. The simple calculation of weight divided by height can be useful for gaining a snapshot of someone’s health, but some research suggests it does not actually paint a full picture.
According to NHS guidelines, a BMI of 18.5 to 24.9 is healthy – but it seems that, in fact, a significant number of people classified as overweight by their BMI are healthy and vice versa.
“BMI is calculated based on a person’s height and weight and so doesn’t take into account how much fat compared with muscle they have or whether any fat in the body tends to be distributed around the waist area,” says Bridget Benelam of the British Nutrition Foundation.
One 2016 study published in the International Journal of Obesity and led by UCLA found that more than 54 million people in the US have been misclassified as “unhealthy” based on their BMI, when in reality they are “cardiometabolically healthy” judging by other markers including cholesterol, blood glucose and blood pressure.
Conversely, about a quarter of people with a healthy BMI have poor cardiometabolic health. Focusing on BMI as the sole indicator of good health could also contribute to weight stigma.
“Whilst BMI is the gold standard measurement for weight, it’s a limited measure as it neglects key factors; age, gender and ethnicity can all impact weight,” says nutritionist Jenna Hope. “Additionally, BMI fails to differentiate between fat mass and fat-free mass. Fat mass is a more important predictor of health than overall weight.”
If BMI is not an entirely accurate indicator, what tests should you do instead? Well, measuring waist circumference is just as important as stepping on the scales, according to a scientific statement published by the American Heart Association in the journal Circulation in 2021.
A beer belly or so-called middle-aged spread could be a sign of visceral adipose tissue (VAT) – a dangerous kind of abdominal fat that wraps around internal organs. Abdominal obesity can put someone at greater risk of cardiovascular disease even if they aren’t overweight or obese based on their BMI. NHS guidelines say that a waist circumference of 94cm (37in) or more for men and 80cm (31.5in) or more for women increases the risk of heart disease, type 2 diabetes, cancer and stroke, regardless of overall body mass.
Research from Loughborough University in 2017 found that people who carry weight around their middle but have a normal BMI are at increased risk of death by any cause compared with those who are obese but carry their weight elsewhere.
As well as measuring waist circumference, there are tests that can be done easily, at home, which offer insight into your cardiovascular health, musculoskeletal strength and general good health. These are the health tests to try today.
Health tests to try at home
Waist circumference is one way to assess whether a person is at risk of abdominal obesity. Measure your waist with a tape measure. Find the point at the bottom of your ribs and the top of your hips and take a measurement breathing out naturally, without sucking in. According to NHS guidelines, you should try and lose weight if your waist measures more than 94cm (37 inches) for men and 80cm (31.5 inches) for women, regardless of your BMI.
Another way of assessing whether someone has a healthy amount of abdominal fat is waist-to-hip ratio (WHR). Measure your hip circumference by standing straight with your legs together and measuring around the widest part of your hips while breathing out naturally. To calculate your WHR divide your waist measurement by your hip measurement. According to the World Health Organisation, a healthy WHR is 0.9 or less for men and 0.85 or less for women.
Stand up and sit down test
Passing the “sit and rise” test is associated with a lower risk of all-cause mortality, according to data published in the European Journal of Preventive Cardiology in 2012. The test is simple: move from standing to a seated position on the floor, and then back up again, without using your hands, arms or knees to support yourself if possible. This only needs to be done once. In the original study on adults aged 51-80, those who did not pass this test of musculoskeletal strength were almost seven times more likely to die within six years than those who could sit down and stand up unaided.