Nutritionist Rose Carr and HFG dietitian Zoe Wilson get to the bottom of what a ‘healthy weight’ really means.
Knowing what your ideal healthy weight should be can be confusing – and at the end of the day, it’s different for all of us. To help you figure out what’s best for your individual health, we take a look at what a ‘healthy weight’ really is. We also decipher whether you can still be healthy while technically overweight, or, on the flipside, whether you can be slim or within a healthy weight range, but unhealthy. To sort the facts from the fiction, read our answers to some of the most commonly asked questions on this tricky topic.
What is our weight comprised of?
Our bodies and our weight are made up of different tissues, which scientists divide into two groups: lean, or fat-free, mass (which includes our muscles, bones and organs) and fat mass. Having either very high or very low fat mass can cause health problems, so it is important to know what a healthy fat mass is for your body, rather than just relying on your total weight as an indicator of your health.
How are body composition and fat mass measured?
Scientists have developed many ways to measure fat mass. Unfortunately, the most reliable methods (such as underwater weighing and body scanning techniques) involve very high-tech and expensive machines, so are generally only used in research labs. Other simpler, less expensive measures are used to get an approximation of body composition. These include skinfold thickness tests using callipers; bioelectrical impedance; the Body Mass index (BMI, see box right), and other body measurements, such as waist circumference and waist-tohip ratio.
So what is a ‘healthy weight’?
The healthy weight range is where there is the least risk of developing weight-related health problems or diseases. It has nothing to do with appearance or what looks best. BMI is generally accepted as a measure of healthy weight, although it’s a less accurate reflection for certain groups of people (see above). BMI is a calculation of the ratio between your weight and height, and is used to estimate the amount of body fat we carry. Another accepted method for determining healthy weight is waist circumference (see over for more detail).
A 2010 study published in the New England Journal of Medicine pooled data from studies involving over 1.4 million Caucasian adults aged 19 to 84 in the USA. It confirmed the association between a BMI above 24.9 and an increased risk of death from disease, and that the least risky BMI range was 20.0 to 24.9. Above 24.9, the risk increased slowly at first, then sharply. As BMI increased past 25 there was a higher risk of developing high blood pressure, type 2 diabetes and cardiovascular disease. A BMI below the healthy weight range can also increase the risk of other health problems, such as osteoporosis and infertility.
Calculate your BMI
BMI = weight (kg) / height (m)²
The BMI cut-off points below are based on associations between weight, chronic disease and mortality, and have been adopted for use internationally by the World Health organisation (WHO). BMI values and their associated risk of developing obesity-related health consequences are:
Less than 18.5 = underweight (low risk of obesity-related health consequences but may increase risk of other health problems)
18.5–24.9 = healthy weight range
25.0–29.9 = overweight (increased risk)
30.0–34.9 = obese class 1 (moderate risk)
35.0–39.9 = obese class 2 (severe risk)
More than 40.0 = obese class 3 (very severe risk)
When is BMI not useful?
While BMI is a reasonable approximation, it has limitations – such as not taking into account age, gender, body type and ethnicity. BMI is a useful initial screening tool to identify people who may have a weight-related problem, but it is not a diagnostic tool. It cannot be used on its own to determine how healthy or unhealthy you are. Other measures, such as blood pressure or fasting blood glucose, are used to see whether someone has any health issues related to being outside of the healthy weight range. Athletes or physically fit people with high muscle mass, women who are pregnant or lactating, and growing children are specifically advised not to use BMI as an indicator of healthy weight. If you fall into one of these groups, then speak with your doctor. You can try other methods, including skin fold testing with a health professional such as an exercise physiologist or a dietitian, or taking your waist measurement.
Other measures of a healthy weight
This may be a better indicator of your health risk as it can determine whether or not you store your fat around your middle (which means a higher risk of certain health problems, see right) rather than around your hips. Use a tape measure and place around the smaller circumference of your natural waist, usually just above the belly button. For the general population, the recommended waist measurement and corresponding risk of obesity-related health consequences are:
While being overweight does carry an increased risk of some health-related problems and diseases, in short – yes, you can be overweight and still healthy. If your BMI is outside the healthy weight range, but you’re physically fit and active and follow a healthy diet, you could be healthier than a person who is within the healthy weight range, but not fit or active and has an unhealthy diet. Your doctor can help evaluate your overall health and what your healthy weight should be. Measures such as your cholesterol level, blood pressure and fasting blood glucose (your blood sugar level before you have eaten anything) will give a more accurate picture of your health than a simple BMI measure. So, it’s best to see your GP if you have any concerns.
Is it possible to be slim, but unhealthy?
Yes it is, and in fact being underweight can be a health risk too. We do need some body fat to be healthy!
Where you store your body fat, how much exercise you do, and your family history are all factors that contribute to how healthy you are, regardless of your weight.
Researchers in Italy were the first to identify what they call ‘normal-weight obesity’. This refers to people who have a BMI within the healthy range, but a higher than normal proportion of body fat, as well as abnormal health indicators normally associated with higher BMI. These indicators may include insulin resistance (an indicator of type 2 diabetes), high cholesterol and high blood pressure.
What we now know is that where you store your fat has different effects on your health. Subcutaneous fat, the fat found just under the skin which we can see and feel, isn’t as bad for our health as visceral fat – which is stored deeper inside the belly and sits around the organs. High amounts of visceral fat are associated with problems such as developing insulin resistance and cardiovascular disease. Scientists in the UK have been conducting MRI scans on people to assess how they store their fat. They found as many as 45 per cent of women with normal BMI scores (20 to 25) actually had higher than normal levels of internal visceral fat. Among men, it was nearly 60 per cent. It seems that people who maintain their weight only with diet and minimal exercise can be at risk of having higher amounts of visceral fat, despite their normal weight.
Your risk of abnormal health indicators is also higher if you have a family history of heart disease or type 2 diabetes. This applies even if you are within the healthy weight range and have regular checkups with your GP to monitor your cholesterol, blood pressure and blood sugar levels.
Is it better to be overweight but fit, or skinny but unfit?
Research has shown that exercising regularly is important in decreasing the amount of visceral fat you have, even if there are no changes in overall weight or BMI. It appears that fitness can counteract at least some of the health risks linked with having high body fat. People who are physically fit and active, but who are in the overweight BMI range, could actually be healthier than people in the healthy weight range who are unfit. However, at BMI 30-plus, some of the health risks from excess body fat may still remain even if we’re physically fit.
A 2010 review compared fit and active obese people (with a BMI of 30–34.9), with unfit and inactive healthy weight people. The authors found the risk of death overall was lower in people with high BMI and good aerobic fitness, compared with those with normal BMI and poor fitness. However, the obese people, even with their high level of physical activity, still had a greater risk for type 2 diabetes and cardiovascular disease, compared to those with a healthy BMI and low physical activity. The Australian Guidelines for Physical activity for adults recommends at least 30 minutes moderate-intensity activity or exercise on most days of the week, with some high-intensity exercise as well if you can.
What’s the best thing I can do if I’m officially overweight?
Losing weight to get into the healthy weight category as defined by BMI is not necessarily viable for everyone. One of the best things you can do is to eat a healthy, balanced diet and be physically active, regardless of your weight (and even if you are already in the normal BMI category). Being active not only helps to avoid weight gain, but also helps reduce the physiological effects of any excess weight. And as an added bonus, it lifts our mood at the same time.
Tips for a more healthy, active you
1. Keep an exercise diary
Researchers have found we often think we’re doing more exercise than we really are. We’re only human, after all! So rather than relying on your memory, keeping a diary of your physical activity each day is a good reality check. You can plan ahead as well as review how much you’re actually doing.
2. Get your heart pumping
Cardiovascular exercise is anything that gets your heart pumping a bit faster. It’s good for your heart and it increases the rate at which you use energy (kilojoules). If the thought of jogging leaves you cold, there are plenty of other alternatives: swimming, dancing, skipping or a gym class will all get your heart rate up; even walking at a faster pace than you usually do will help.
3. Do resistance exercise
Using weights or doing body weight resistance exercises will use and develop muscle strength, which in turn helps to burn more kilojoules. Digging in the garden and lugging bags of compost might give us some resistance exercise, but unless we have a physically active job or hobby, we probably won’t get a lot without making an effort to do some body weight exercise. Try using some weights, a resistance band, or go to a specific gym class.
4. Add incidental exercise
Look for opportunities to increase the amount of movement you do, rather than to lessen it. Wherever you can, use stairs instead of taking a lift; don’t park right where you need to be, but have a short walk instead; go and talk to your co-worker in the far office rather than sending an email; and think of the walk to the printer as a good thing rather than an inconvenience.
5. More is better
Once you’ve got yourself moving on a regular basis think about how you can increase your fitness even more. Can you increase your time spent exercising, the frequency, or the level of exertion? Also, try mixing up the type of exercise you do – you could try a new class at the gym, or give a new sport a go!
Did you know? If you’re overweight, losing just 5-10% of your body weight can reduce your risk of developing a chronic disease by reducing blood pressure, cholesterol and blood sugar levels.