BMI – Severely Underweight
If your Body Mass Index score comes in at less than 16, you’re considered severely underweight by current World Health Organisation standards. Being severely underweight can be a sign of serious malnutrition or other major health issues - including eating disorders such as anorexia nervosa or bulimia.
There are several medical reasons why a person might be excessively thin. These include hyperthyroidism, diabetes, tuberculosis, depression, HIV/Aids or cancer. Some medications can suppress appetite and excessive exercise (with an inadequate diet) can also cause weight loss.
Medical conditions like cystic fibrosis and coeliac disease can also affect weight, as can enzyme deficiencies and too much stress . If your BMI indicates you’re severely underweight, seek medical advice. The old saying “you can’t be too rich or too thin” isn’t true: being too thin can be dangerous to your health. Consult your doctor for more information.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI – Underweight
A Body Mass Index measurement of less than 18.5 falls into the Underweight category. Being underweight could mean your body isn’t getting the nutrition it needs to function in a healthy manner. It may also mean that medical issues (which you might not even be aware of) are possibly contributing to the problem.
Some people seem to have trouble putting on weight – even when they want to. While there can be many reasons for this, chronic thinness can sometimes be a clue that an underlying medical condition is at fault. Being underweight can be a symptom of hyperthyroidism, cancer, diabetes, HIV/Aids or tuberculosis.
Your mental state can also lead to weight fluctuations: depression and stress can trigger weight loss if left untreated. If you’re underweight, your health professional might also test you for cystic fibrosis, coeliac disease or enzyme deficiencies. Consult your doctor for more information.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI – Normal Range
If your BMI measurement is above 18.5 but below 25, the World Health Organisation considers you to be in the Normal Range weight category.
With studies showing that Australia’s obesity rates are rising faster than anywhere else on the planet , having a BMI in the normal range is good news – up to a point. It doesn’t mean you can forget about proper diet, exercise and healthy lifestyle habits – it just means you’re currently within normal weight parameters for your height.
You should routinely check your BMI, especially if you’re close to either end of the ‘normal’ scale. And of course, it’s quite possible to have a healthy-looking weight but still be affected by an entire range of medical problems. Smoking, excessive alcohol consumption, dubious nutrition and an aversion to exercise can affect your health and longevity at any weight, so don’t become too complacent!1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI – Overweight
A Body Mass Index measurement of 25 to 29.99 is categorised as Overweight by the World Health Organisation. This weight category is also sometimes referred to as ‘pre-obese’, as it sits between Normal Range and Obesity Class 1.
Being overweight is a sign that you should take action to improve your health. Steady weight gain should be managed as early as possible because it affects your energy levels, fitness status and overall wellbeing.
If you’re overweight, you’re more at risk from health issues such as heart disease, type-2 diabetes, gall bladder disease, some cancers, sleeping problems, high blood pressure and much more.
Going on a ‘crash diet’ is not the way to deal with weight gain. Success is more about changing shopping and eating habits and becoming more consistently active. Check out this Healthy Weight website for ideas and consult your doctor for more information.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI – Obese Class 1
A Body Mass Index measurement of 30 to 34.99 indicates that a person falls into the Obesity Class 1 category.
Obesity rates in Australia have more than doubled in the past 20 years, and obesity has now overtaken smoking as the leading cause of premature death and illness in this country. It’s currently the largest single threat to public health in Australia.
Being obese isn’t just about how a person looks – it’s about their susceptibility to long-term medical problems. Obesity is associated with a whole range of serious health issues including chronic kidney disease, cardiovascular disease, asthma, hypertension and stroke, just to name a few.
If your BMI reading is over 30, this means you are clinically obese . The good news is that there are many positive strategies you can pursue to get back to a healthy weight. Consult your doctor for advice.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI – Obese Class 2
A Body Mass Index measurement of 35 to 39.99 represents the Obese Class 2 weight category.
More than 5 million Australians are obese (BMI exceeding 30) and it’s predicted that if current trends continue, our children, by the time they reach 20 years of age, will have a shorter lifespan than previous generations, due to obesity.
Obesity is certainly a major health issue, but it’s one that can be fixed. Consuming a wide variety of foods from the 5 food groups is a great start – and you should aim for 2 serves of fruit and 5 serves of veggies each day. Cut right down on salty, sugar-laden, fatty foods. Drink water instead of soft drinks – you’ll save lots of money and bypass lots of calories. Move more, sit less and think about the importance of portion control. Consult your doctor for further information.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
BMI ‐ Obese Class 3
A Body Mass Index measurement in excess of 40 indicates a weight category of Obese Class 3. The World Health Organisation defines obesity within three levels: Class 1 (BMI of 30 - 34.99), Class 2 (BMI of 35 – 39.99) and Class 3 (BMI over 40), the most severe.
At Obese Class 3, the human body is at serious risk from a range of health complications. Some of these risks are associated with the weight itself (breathlessness, sleep apnoea, fatigue, social isolation, etc.) while others are associated with the metabolic consequences (type 2 diabetes, hypertension, insulin resistance, atherosclerosis, etc.).
This level of obesity takes a long time to develop, so returning to a healthy weight takes time as well. But by making the right lifestyle choices and accessing helpful online information resources, it’s never too late to trim down. Consult your doctor for more information.1http://apps.who.int/bmi/index.jsp?introPage=intro_3.html
Body Mass Index (BMI) is a useful way of measuring whether you’re in a healthy weight range for your height. BMI helps in assessing your risk for chronic disease, but should never be used in isolation. It’s important to understand other risk factors including waist circumference. While you can’t do much about your family history, age, gender or ethnic background, other common risk factors can be proactively controlled - including smoking, high blood pressure, physical inactivity, unhealthy diet, diabetes and high cholesterol.
Our handy BMI tool works by dividing your weight in kilograms by your height in metres squared. This gives you a better idea which category your body currently falls under: Severely Underweight, Underweight, Normal, Overweight, Obese Class 1, Obese Class 2 or Obese Class 3.
BMI is an estimate only and does not factor in age, ethnicity, body composition or gender. It should not be used for children or pregnant women. Before making any major dietary or lifestyle changes, you should always speak to your doctor, health practitioner or accredited dietitian.
There’s plenty you can do to take action against your personal health risks, and checking your BMI measurement is a great first step.