So you think you’re fat?
There are various ways of assessing whether you need to lose weight. Which are reliable?
Six ways to measure up
- BMI (Body Mass Index). This is used to classify people as underweight, healthy, overweight or obese. It’s your weight in kilograms divided by the square of your height in metres.
‘BMI is a useful tool and when combined with measuring your waist circumference, it can help indicate future health risks’, says Allison Clark, Dietician and Spokesperson for the BDA (British Dietetic Association).
A muscular person might have a healthy BMI when their body fat is healthy, as muscle weighs more than fat. BMI also fails to take a person’s body shape into consideration – for example, a slim woman with a podgy stomach might have a healthy BMI but the fat she carries could still be a risk to hear health. New information from NICE (the National Institute for Health and Care Excellence) also reveals that the level of body fat varies within ethnic groups.
- Waist circumference. To measure yours, feel your hip bone on one side. Move upwards until you can feel the bones of your bottom rib. Halfway between the two is your waist. For women an ideal measurement is less than 32 inches, high is 32 to 25 inches and very high is more than 40 inches.
Professor David Haslam from The National Oesity Forum, says: ‘Waist circumference is the best measure of assessing someone’s weight related health.’
‘If you don’t measure properly you could get a wrong reading. Also, if you suffer with MPS or OBS bloating you could get inaccuracies. So meaure yourself after your period, or first thing in the morning when your waist tends to be flattest, ‘ says Allison Clark.
- New Trefethen BMI. Professor Nick Trefethen, Professor at Numerical Analysis at Oxford University, recently devised a new formulation (1.3 x weight divided by height to the power of 2.5), which is designed to be more accurate than the current BMI.
There don’t seem to be any as yet.
This method hasn’t been accepted by the health profession. Professor Haslam says: ‘This adds nothing of clinical relevance.’
- Waist to hip ratio. Storing a lot of excess fat around your abdomen, rather than on your bottom or thighs, can increase your risk of Type 2 diabetes or heart problems. To calculate your waist to hip ratio, measure your hips, measure your waist and divide the waist result by the hip result. A ratio of 0.85 or more in women is a problem.
NHS choices says this is a simple way to work out the risk of your health.
‘This requires more than one measurement and a calculation and so is more error-prone, ‘ says Professor Haslam.
- BIA (bioelectrical impedance analysis) – a painless low electric current is sent through the body to compute how much body fat you have. Machine prices vary hugely and health professionals tend to think the more expensive machines (we’re talking thousands of pounds) are more accurate. These are available to use in clinics and some gyms.
‘Good quality machines can give an accurate reading of your total body fat,’ says Professor Jimmy Bell, Professor of Biochemistry at Imperial College, London.
‘ These machines can’t specifically tell you where fat is stored in your body, and it’s the whereabouts that can be problematic,’ he adds.
- BVI (body volume index scanner). This creates a 3D visual of your body so your shape and weight distribution can be measured precisely.
‘A BVI scan works out where the weight and fat are distributed. Depending on where the weight and fat actually are on your body is the only real way to tell whether you have a health risk or not,’ says Richard Barnes of Select Research, one of the creative team behind BVI.
BVI scanners aren’t readily available at the moment but this is soon set to change with the introduction of a remote scanner via a webcam.
Is measuring dangerous?
Food psychologist Dr Christy Fergusson thinks potentially yes. She says: ‘Getting caught up with looking at the scales or working out your BMI is not an accurate way of measuring how healthy you are. It can also create obsessive behaviour.’ She recommends: ‘Notice how your clothes are fitting and how you look and feel. For example, how is your digestive system and what are your energy levels like?
‘If your waistband is tight or you feel sluggish, look for ways to get healthier, such as doing a bit more exercise. Small changes can give big results without making you feel overwhelmed.’
Are you fat on the inside?
We’re all so obsessed with weight loss, but what about internal fat? Could you be thin on the outside but fat on the inside with ‘hidden’ fat around and inside your internal organs? This issue has been linked to health problems such as heart disease and diabetes. Scans can show how much internal fat you have, but they’re pricey and not readily available. Professor Jimmy Bell says: ‘These scanning procedures are not necessary for the average person.’
Instead he suggests you measure your waist, and if you’re worried about having too much internal fat do more exercise and reduce the amount of refined carbohydrates you eat (such as white bread, pasta and rice).
Do you feel yourself constantly checking the scales? Have you considered how much internal body fat you may have?