Body weight can be measured in several ways. One of the most popular methods that show whether or not a person is overweight is the body mass index (BMI). Body mass index is used to determine whether you are in a healthy weight range for your height. It is useful to consider BMI alongside waist circumference. Because, waist measurement helps to assess risk by measuring the amount of fat carried around your middle.
A high body mass index can be an indicator of high body fatness. But it is only an estimate. It doesn’t take into account age, ethnicity, gender and body composition. It gives you an idea of whether you’re ‘underweight’, a ‘healthy’ weight, ‘overweight’, or ‘obese‘ for your height. BMI is one type of tool to help health professionals assess the risk for chronic disease.
Why waist size also matters
Measuring your waist is a good way to check you’re not carrying too much fat around your stomach. This can raise your risk of health problems such as heart disease, type 2 diabetes and stroke. However, you can have a healthy BMI and still have excess tummy fat. This means you’re still at risk of developing these conditions.
To measure your waist:
- Find the bottom of your ribs and the top of your hips.
- Wrap a tape measure around your waist midway between these points.
- Breathe out naturally before taking the measurement.
In women, a waist size of 88 cm (35 in.) or more raises the chance for disease. In men, a waist size of 102 cm (40 in.) or more raises the chance for disease. Waist size cut-off may be lower for some people.
How to calculate Body Mass Index
Body Mass Index is a simple calculation using a person’s height and weight. The formula is BMI = kg/m2 where kg is a person’s weight in kilograms and m2 is their height in metres squared. A body mass index of 25.0 or more is overweight, while the healthy range is 18.5 to 24.9. Body mass index applies to most adults 18-65 years. However, there are loads of online calculators that’ll pump out your BMI once you drop in your stats.
Understanding your BMI result
Use the chart below to locate your height and weight. The shaded regions on the chart correspond to normal and overweight ranges based on body mass index (BMI). Keep in mind that this is only a guide. It is not a tool to determine ideal body weight. It is a tool to help you see whether your weight is increasing your risk for disease.
However, people who are very muscular or those who have very little muscle may not get an accurate BMI by using their height and weight alone. Because, muscle weighs more than fat. Therefore, a muscular person may appear to have a higher BMI. For adults 18 years and older a BMI of:
- below 18.5 (shown in white) is underweight.
- 18.5 to 24.9 (green) is healthy.
- 25 to 29.9 (yellow) is overweight.
- 30 or higher (red) is obese.
Having a BMI over 30 places you at risk for medical conditions such as diabetes, high blood pressure and heart problems. A BMI over 40 indicates that a person is morbidly obese.
For children and young people aged 2 to 18, the BMI calculator takes into account age and gender as well as height and weight. Overweight children are at increased risk of a variety of health conditions, and they’re also more likely to be overweight as adults.
The BMI calculator works out if a child or young person is:
- underweight – on the 2nd centile or below
- healthy weight – between the 2nd and 91st centiles
- overweight – 91st centile or above
- obese – 98th centile or above
A child’s BMI is expressed as a “centile” to show how their BMI compares to children who took part in national surveys.
Getting to a healthy weight
Losing weight in a healthy way is one of the best things you can do for your long-term health. But it takes time and requires commitment. Many weight loss books and crash diets often suggest quick unhealthy ways to lose weight. This won’t help you maintain weight loss in the long-term.
It is all about mindset, don’t think about it as ‘going on a diet’ which is short-term, but as a choice to lead a healthier life. Think about nourishing your body such as with fresh foods, reducing or removing highly processed foods. Also take every opportunity to be as active as you can, to achieve your weight loss goal.