To maintain a healthy weight, you need to balance the amount of calories you consume through food and drink with the amount of calories you burn through physical activity.
To lose weight in a healthy way, you need to use more energy than you consume by eating a healthy, balanced diet with fewer calories while increasing your physical activity.
A body mass index (BMI) above the healthy weight range, or too much fat around your waist, can increase your risk of serious health problems like heart disease, type 2 diabetes, stroke and certain cancers.
Use the BMI calculator below to find out if you are a healthy weight.
To work out your BMI:
divide your weight in kilograms (kg) by your height in metres (m)
then divide the answer by your height again to get your BMI
if you weigh 70kg and you're 1.75m tall, divide 70 by 1.75 – the answer is 40
then divide 40 by 1.75 – the answer is 22.9
your BMI is 22.9kg/m2
For most adults, an ideal BMI is in the 18.5 to 24.9 range.
If your BMI is:
below 18.5 – you're in the underweight range
between 18.5 and 24.9 – you're in the healthy weight range
between 25 and 29.9 – you're in the overweight range
between 30 and 39.9 – you're in the obese range
Overweight and Obesity
Being overweight or obese can have a serious impact on health. Carrying extra fat leads to serious health consequences such as cardiovascular disease (mainly heart disease and stroke), type 2 diabetes, musculoskeletal disorders like osteoarthritis, and some cancers.
What is not widely known is that the risk of health problems starts when someone is only very slightly overweight, and that the likelihood of problems increases as someone becomes more and more overweight. Many of these conditions cause long-term suffering for individuals and families.
The good news is that overweight and obesity are largely preventable. The key to success is to achieve an energy balance between calories consumed on one hand, and calories used on the other hand.
To reach this goal, people can limit energy intake from total fats and shift fat consumption away from saturated fats to unsaturated fats; increase consumption of fruit and vegetables, as well as legumes, whole grains and nuts; and limit their intake of sugars. And to increase calories used, people can boost their levels of physical activity - to at least 30 minutes of regular, moderate-intensity activity on most days.
Why waist size matters
Measuring your waist is a good way to check you're not carrying too much fat around your stomach, which can raise your risk of heart disease, type 2 diabetes and stroke.
You can have a healthy BMI and still have excess tummy fat – meaning you're still at risk of developing these diseases.
If your BMI is below 18.5, this suggests that your weight may be too low.
Being underweight isn't good for your health.
Weighing too little can contribute to a weakened immune system, fragile bones and feeling tired.
Why are you underweight?
Have you felt unwell? There might be an underlying medical cause for your low weight, such as an overactive thyroid.
Have you been finding it difficult to make time to have a healthy, balanced diet with regular meals?
Have you lost your appetite, perhaps because you're worried or stressed?
Have you been trying to lose weight?
If you feel anxious or worried when you think about food, or feel that stress or low self-esteem are affecting the way you eat, you may have an eating disorder.
If you think you may have an eating disorder, talk to someone you trust and consider speaking to your GP, because help is available.
If you're concerned about someone else, find out how you can support them.
Being underweight isn't good for you. It could cause:
Nutritional deficiencies: if you're underweight, it's likely that you're not consuming a healthy, balanced diet, which can lead to you lacking nutrients that your body needs to work properly. Calcium, for example, is important for the maintenance of strong and healthy bones. If you don't get enough calcium, you risk developing osteoporosis (fragile bone disease) in later life. If you're not consuming enough iron, you may develop anaemia, which can leave you feeling drained and tired.
Weakened immune system: your immune system isn't 100% when you're underweight, so you're more likely to catch a cold, the flu or other infections.
Fertility problems: women who are underweight can find that their periods stop.