What does Body Mass Index (BMI) mean?
Doctors use a measure called the body mass index (BMI) as a guide to whether someone is a healthy weight for their height. It is not perfect, but it is a useful guide for most people.
BMI divides an adult’s weight in kilograms by their height in metres squared. Use the BMI calculator on the NHS website to find out what range your weight is in.
For people who are Black, Asian or belong to another ethnic minority group the risk of type 2 diabetes and other long term conditions starts to increase at a BMI of 23. Even though this is in the healthy range, it is a good idea to keep an eye on your weight if your BMI is 23 or more.
If you are experiencing symptoms like fluid retention in the abdomen (ascites) this will affect your weight and your BMI can be misleading. Speak to your doctor or dietitian for advice including how to reduce your symptoms through diet.
Understanding weight gain and weight loss
Energy balance, calories and weight
To reach and stay at a healthy weight you need to balance the energy you get from your food and drinks with the energy you use.
Energy is measured in calories. If you take in fewer calories than your body uses you will lose weight. And if you take in more calories than you use you will put on weight.
The amount of energy your body needs is affected by:
- whether you are a man or a woman
- how old you are
- how much you weigh and how muscular you are
- how physically active you are
As a rule of thumb a healthy man uses about 2,500 calories a day. And a healthy woman uses about 2,000 calories a day.
If you are overweight, aim to lose weight steadily. Losing 0.5 to 2lb (0.25 to 1kg) a week is a safe and realistic goal.
There is some evidence that very low calorie diets can be used to treat or manage metabolic disease (including NAFLD). Talk to your doctor before starting to follow a diet with very low calorie intake or that cuts out certain types of food altogether.
If you have a BMI of 35 or more and are struggling to lose weight ask to be seen by specialist weight management services. They have access to more specialist teams and will consider a wide range of treatments that may include medicines or surgery.
Lose weight sensibly – make small changes for good
For most people it is healthier to lose weight steadily over time. To lose weight you need to use more calories than you take in. There are 2 ways to do this. Eat a healthy, balanced diet. And be more physically active.
They are big changes and it can feel overwhelming. But you don’t have to make them all in one go. You can break them both down into small changes that build up over time. Don’t put pressure on yourself to be perfect. Think about how far you’ve come, take it one step at a time and keep going.
There are lots of small ways to start losing weight. The best tips are the ones that work for you and you can stick with. Be realistic and make one or two changes at a time. Once they have become part of your normal life, add another small change.
Thinking about your eating habits generally can be a good place to start.
- Plan your meals in advance so you stay on track and have the food and drinks you need to hand.
- Start your day with a healthy breakfast such as porridge, reduced sugar cereal or scrambled eggs on wholegrain toast. It will give you energy and keep you going until lunchtime.
- If you tend to get hungry between meals, swap snacks like chocolate and crisps for healthier options such as a piece of fruit, a handful of nuts, or natural or Greek yoghurt.
- Eat at about the same times each day.
- Don’t eat on the go. Take your time and focus on your meal.
- Think about your drinks too.
Most importantly, enjoy your food. Make sure you include dishes you like. Share meals with family and friends. And remember you can have a treat every now and then.