Being too light or too heavy can increase our chances of ill health. BMI is a measure of weight in relation to height and can be a useful indicator of health – current wisdom says a BMI of 18.5 to 24.9 is healthy. It doesn’t, however, take into account body composition. Some experts say BMI leads short people to believe they’re thinner than they are and tall people to believe they’re fatter. ‘But it’s still an indicator of how you’re doing,’ says HFG expert Professor David Haslam, chair of the National Obesity Forum. ‘If your BMI goes up or down from your norm, it’s handy to know and ask yourself why.
‘Recent studies also show that, as we age, being a bit heavier and maintaining weight can be better for our health,’ adds David. ‘Those aged 70 and over are better off with a BMI of between 20 and 30, as weight loss can lead to a reduction in muscle mass and bone density.’
Calculate it by taking your weight in kg and dividing it by your height in metres squared – or simply download a free BMI calculator for an iPhone, iPad or iPod touch via nhs.uk/tools.
BMI and weight alone can’t identify how much of your body is muscle, fat, bone or water. One way to measure these is by Bioelectrical Impedance Analysis (BIA), which uses electrodes to estimate your total body water, then fat-free body mass and body fat (the most accurate BIA devices are known as tetrapolar and have at least four electrodes). Ideal levels of body fat are 18–24% for men and 18–30% for women.
We like the Tanita body composition BIA scales, which have inbuilt electrodes in the foot sensor pads. Many gyms now have scales that measure the amount of fat you have, as well as your weight.
Too much fat around your abdomen increases the risk of several diseases, including type 2 diabetes and heart disease. There are two quick measurements you can take at home:
Waist size This is a measurement of the widest part of your waist, where your belly button is. A healthy waist measurement for men should be no greater than 94cm (37in) and for women, no more than 80cm (31.5in). Above this you have a higher risk of health problems – and the further away from these measurements your waist is, the greater the risk.
Waist-to-hip ratio Your waist should be smaller than your hips for optimal health. Measure your waist, then your hips (around the widest part) and divide your waist measurement by your hip measurement. A ratio of 1 or more in men or 0.85 or more in women indicates you’re carrying too much fat around your middle.
Can you move in all the ways you want to? Are you able to twist your torso and look behind you? Flexibility is important for our bodies, to help prevent strains and protect against joint pain. A good gym will have a range of flexibility tests, but here’s one you can do at home:
Sit down with your legs stretched out in front of you with your feet flat against a wall. How close your fingers can get to the wall gives you a measure of how flexible you are. If you can get your palms on the wall touch, it’s a top score; if your fingers reach, that’s good; average is 1cm–12cm away (men) or 1cm–10cm (women); poor is over 13cm away (men) or over 11cm (women).
The best time to measure your resting heart rate (RHR) is first thing in the morning before you get out of bed. The NHS states that most adults have an RHR of 60–100 bpm. The fitter you are, the lower it is (some athletes may have an RHR of 40–60bpm or lower!) Your risk of cardiovascular disease and death from other diseases reduces as your heart rate decreases. If you think your RHR is consistently under 40 or over 120bpm, see your GP – although this could just be normal for you.
Find the pulse on the inside of your wrist and put your index and middle finger on the thumb side. Count the beats for one minute (bmp) (or 30 seconds, then multiply by two).
There are smartphone apps that let you keep track of your heart rate at various times of day. We like Azumio Instant Heart Rate.