BMI: Is it the be all and end all
How do you measure health? We look at BMI and some other indicators of your health status.
Your BMI is calculated by dividing your weight in kilograms by your height in metres squared.
To calculate your BMI, click here
“Typically we say a healthy BMI is between 18.5–24.9kg/m2,” explains Bupa dietitian Rosalyn D’Angelo. She notes however that an individual’s BMI isn’t always an accurate representation of their weight or health.
For example, BMI tends to overestimate obesity among shorter people and underestimate it among taller people. Therefore, D’Angelo explains, BMI shouldn’t be used as a guide for adults who are very short (less than 150cm) or very tall (more than 190cm).
“What the BMI equation does not look at is body composition, or body shape. We say that BMI is an approximate measure of your total body fat – and it is better used on a population level – not to assess an individual,” says D’Angelo.
“We know that muscle is very heavy and many elite athletes who carry more muscle than your average adult would be classified as ‘obese’ by the BMI equation, but we know that they are probably not at risk of obesity-related chronic diseases.”
It can also be an inaccurate measure for pregnant women, children, and older people. For some ethnic groups, including people of Asian, Aboriginal or Torres Strait Islander descent, the range that indicates a healthy weight may need to be adjusted.
A different measure
“Your waist circumference is a strong predictor of your health risk,” offers D’Angelo and a complements your BMI score.
She explains that the fat we carry around our hips and thighs is ‘subcutaneous fat’ (the fat that sits just below the skin), whereas the fat around the waist is called ‘visceral fat’ and stores around our vital organs, such as our pancreas, stomach and intestines.
“This visceral fat doesn’t just sit there,” says D’Angelo. “We call it ‘metabolically active’ as it releases nasties called ‘cytokines’ that cause inflammation. We know that excess fat around the waist can increase your cholesterol levels, blood sugar levels and blood pressure. This in turn can increase your risk of chronic diseases such as type 2 diabetes and heart disease.”
She advises men should aim for a waist circumference of less than 94cm and women of less than 80cm. Men with a waist circumference above 102cm and women who are above 88cm have a substantially greater risk.
“It is important to look beyond your BMI and also ‘know your numbers’,” says D’Angelo. “There are healthy ranges set for a range of different risk factors for chronic disease.” She lists the following as the main ones to monitor.
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You get four cholesterol readings from a fasting cholesterol test:
• Total cholesterol
• HDL ‘good’ cholesterol.
• LDL ‘bad’ cholesterol.
If you have a family history of heart disease it is especially important that you know how your cholesterol is looking.
Diet and lifestyle changes can improve cholesterol levels, but they are also influenced by genetics. So find out what you can do to help keep your levels in a healthy range.
Blood glucose levels
Glucose is a type of sugar. Your body uses glucose as fuel for energy, with a hormone called insulin helping cells to take in glucose from your blood. There are tests to check how much glucose is in your blood stream in a fasting state and the results can be an indicator of having or developing type 2 diabetes.
While diet and lifestyle habits can affect blood pressure, also to can stress and underlying medical conditions. So it’s important to know what your blood pressure is, and, if it’s high, have a chat with your doctor about what you can do to lower it.
Interestingly, many people’s blood pressure can go up at the doctor’s because they’re anxious. We call this ‘white coat hypertension’. A 24-hour blood pressure monitor can give you a clearer picture of what’s really going on with your blood pressure, if your doctor wants to know more.
D’Angelo notes the importance of staying in touch with your GP throughout life: “Don’t just go to the doctor when you get sick. Get your screening tests done. A blood test only takes a few minutes. Prevention is much better than cure.”
Aim for a healthy weight
“Excess weight can affect you in many ways such as worsening the symptoms of asthma, increasing your risk of sleep apnoea, and the extra weight can put extra pressure on your joints,” says D’Angelo. “So even if all your blood test results are within range, there are still plenty of reasons to ensure you’re a healthy weight.”