Healthy weight for adults

Your health expert: Christina Merryfield, Senior Specialist Dietitian, Cromwell Hospital
Content editor review by Pippa Coulter, March 2023
Next review due, March 2026

Keeping to a healthy weight will help to lower the risk of various health conditions.

Here we explain how to work out whether or not you’re a healthy weight and what changes to make if you’re not.

How weight affects health

If you’re overweight or obese, your risk of developing associated health problems may be increased. These include conditions such as:

You may also be more likely to have trouble with symptoms like breathlessness and lower back pain. Being obese can also make operations and having an anaesthetic more risky.

Being underweight may be caused by not getting enough of the right nutrients in your diet. This can also increase your risk of certain health problems, such as:

  • reduced muscle strength
  • increased risk of illnesses and infections
  • increased risk of some heart conditions
  • fertility problems
  • slower wound healing

Keeping to a healthy weight will reduce your chance of developing these health problems.

What is a healthy weight

A healthy weight for you will depend on your height and other factors, such as whether you have a lot of muscle. The most simple and straightforward way of measuring if you’re a healthy weight for your height is to calculate your body mass index (BMI). It’s also useful to look at your waist circumference and how this compares to your height (your waist-to-height ratio). This gives a better idea of where you store fat on your body.

BMI (body mass index)

BMI can give an estimate of whether you’re a healthy weight for your height.

You can work out your BMI using our BMI calculator.

Your BMI will fall into one of the following categories.

  • Less than 18.5 = underweight
  • 18.5–24.9 = healthy weight
  • 25–29.9 = overweight
  • 30 and above = obese

These categories may not be accurate for everyone. This includes if you have a Black African, African–Caribbean, Asian or Middle Eastern background. We describe more on this below.

Limitations with BMI

Knowing your BMI is a simple way to learn more about your weight, but it isn’t perfect. It can’t tell you whether you’re a healthy weight on its own. BMI only looks at your height and weight. It doesn’t take into account other factors like your age, sex, ethnicity and amount of body fat. This means it isn’t always very accurate or as useful in certain groups of people. These include the following.

  • Children. Children’s weight changes a lot as they grow. A child’s BMI is assessed by comparing it to data on others in the same age group. This gives an idea of whether it’s higher or lower than average.
  • Having a lot of muscle. This can mean you weigh more, giving you a higher BMI, in the overweight or obese category. But you may actually have very little body fat – so your weight is still healthy for you.
  • Older people (over the age of 65). You may lose muscle mass as you get older. This may result in you having a low or a healthy BMI, when your body fat is actually high. On the other hand, maintaining a slightly higher BMI when you’re older can help to protect against certain health problems.
  • Certain ethnic groups including people of Black African, African–Caribbean, Asian and Middle Eastern descent. In these groups, your risk of health problems such as type 2 diabetes is greater at a lower BMI. You’re classed as overweight if you have a BMI of 23 to 27.4, and obese if your BMI is 27.5 or above.

Waist circumference and waist-to-height ratio

Where you store fat on your body is an important indicator of whether your weight is a risk to your health. Storing fat around your tummy (abdomen) is worse for your health than storing it around your hips and thighs.

Your waist-to-height ratio (how your waist circumference compares to your height) gives you a good indication of how much fat you store around your tummy. This is something you can work out yourself.

Measuring your waist circumference

First of all, you need to measure your waist circumference properly.

  • While you’re standing, wrap a tape measure around your middle. The correct place to measure your waist is midway between the top of your hips and the bottom of your rib cage. This is usually just above your belly button.
  • Keep the tape snug around your waist but don’t pull it in.
  • Breathe out naturally and measure your waist.

Calculating waist-to-height ratio

Measure your height using the same units (either centimetres or inches). You can use an online tool if needed to convert your measurements to the same units. To work out your waist-to-height ratio, divide your waist measurement by your height measurement. Use a calculator or your phone to do this (waist ÷ height = ratio). The answer should be a decimal number. Here is how waist-to-height ratio affects your health risks.

  • 0.4 to 0.49 = healthy amount of fat around your middle, no increased health risks
  • 0.5 to 0.59 = increased fat around your middle, increased health risks
  • 0.6 or more = high amount of fat around your middle, further increased health risks

A good way to think of it is that you should try to keep your waist to half your height (this gives you a waist-to-height ratio below 0.5). These categories are the same no matter what sex and ethnicity you are. They also apply to people with high muscle mass.

Waist circumference and health risks

Guidelines have previously recommended just looking at waist circumference to measure tummy fat. Using this system, people were classed as having a higher risk of health problems if they had a waist circumference of:

  • 90cm or more for men of African–Caribbean, South Asian, Chinese and Japanese origin
  • 94cm or more for men of white European, Black African, Middle Eastern and mixed origin
  • 80cm or more for women of any background

Some people may still use these measurements to assess health risks. But waist-to-height ratio is now thought to give you a better idea.

Reasons for weight gain or loss

Changes to your weight are mainly down to the balance between calories you take in through food and drink, and calories you use in activity. Put simply, you'll:

  • gain weight if you take in more calories than you use up
  • lose weight if you use up more calories than you take in
  • maintain your weight if you balance the calories you take in with the calories you use up

Other factors can also make a difference – for instance, your genetic make-up can sometimes make you more likely to put weight on. Other things that can affect your weight include the following.

  • Getting older. As you get older, you lose muscle mass and gain body fat instead. Your metabolism also slows down and you have lower energy requirements. This makes it easier to put on weight.
  • Menopause. Weight gain during menopause may be partly due to falling levels of the hormone oestrogen in your body. This is in addition to the changes that happen to your body as you get older, described above.
  • Malnutrition in old age. Although weight gain is common as you age, people in the oldest age groups (above 75) are also at risk of becoming underweight. This may be due to difficulty eating, cooking and preparing food. Older people may also be more likely to have a poor appetite and to have health conditions.
  • Medicines. Certain medicines, including steroids, some types of contraceptives and some antidepressants can cause an increase in weight. Other medicines may reduce your appetite, change your taste or affect your digestive system, leading to weight loss.
  • Medical conditions. Conditions that affect hormone levels, such as polycystic ovary syndrome and underactive thyroid can cause weight gain. Meanwhile, living with a long-term health condition like diabetes or kidney disease can be associated with weight loss. Digestive problems, depression and cancer can also cause weight loss.

Reaching a healthy weight

If you're currently over or underweight, making some changes to get to your ideal weight will really benefit your health.

If you’re overweight or obese

If you’re overweight, aim to reach a healthy BMI and waist-to-height ratio by losing weight gradually. A good target to aim for is losing about 0.5 to 1kg (1 to 2lb) a week. To lose weight, you'll need to use up more calories than you take in from food and drink. Reducing your calorie intake and increasing how much activity you do can both help.

It's worth thinking about the following points.

  • What you eat. Eating foods high in fat and sugar will make you more likely to put on weight.
  • How much you eat. Many people eat much larger portion sizes than they need.
  • How you eat. Eating quickly or when you’re doing other things, like watching TV, can result in overeating. Try to eat slowly, focusing on your food.
  • How much alcohol you drink. Alcohol is high in calories and can contribute to weight gain.
  • How much activity you do. Looking for ways to be more active can help you to lose weight and keep it off.

If you’re underweight

Being underweight means you might not be getting all the nutrients, vitamins and minerals that your body needs to be healthy. To put on weight, you will need to try to increase your calorie intake by eating a balanced and nutritious diet. Healthy ideas to boost your calorie intake and increase your weight include the following.

  • Try to eat little and often. Aim to have nutritious snacks in between meals, like cheese and crackers, creamy yogurt, flapjacks, nuts and seeds.
  • Avoid low fat and diet versions of foods and drinks. Go for higher fat options of milk, cheese, cream and other foods until you reach your ideal weight.
  • Foods that are high in protein can help to build you up. These include meat, fish, eggs, nuts, beans, pulses and meat-free protein alternatives.
  • Add cheese to sauces, potatoes and vegetables, and milk powder to mashed potato, puddings and soups to increase energy and protein.
  • Have milky drinks, like hot chocolate, malted drinks, smoothies and milkshakes.
  • Have some ready meals and other foods that are easy to snack on for times when you don’t feel up to preparing food.

If you have a health condition, talk to your doctor or a dietitian first before making any changes to your diet.

Your body mass index (BMI) can usually give you a good idea of whether you’re a healthy weight for your height. Our BMI calculator can tell you what the ideal weight is for you. It is best to look at your BMI together with your waist-to-height ratio to see whether your weight affects your health.

See our section on how to find out your ideal weight for more details.

You can work out your body mass index (BMI) and see whether it is healthy using our BMI calculator. The categories for having a healthy BMI or being overweight or obese are the same for adults of all ages. They can be different for different ethnic groups, though. See our what is a healthy weight section to find out more.

Body mass index (BMI) isn’t a very accurate way of assessing weight in certain groups of people. If you’re very muscular, this can give you a high BMI, even if you have little body fat. It can be more useful to look at your waist-to-height ratio. For more information, see our section on what is a healthy weight.

If you need to lose weight, it’s best to do so gradually. You can do this by reducing your calorie intake and increasing how much activity you do. Aim for a weight loss of around 0.5 to 1kg (1 to 2lb) a week. See our reaching a healthy weight section for more information.

Your metabolism tends to slow down as you get older. Your energy requirements are also usually lower than when you were younger (you need fewer calories from food). If you carry on eating the same amount of food, this means you may put on weight. See our section on reasons for weight gain or loss to find out more.

Your waist-to-height ratio measures how your waist circumference compares to your height. It’s good to aim for a waist-to-height ratio of below 0.5. This means your waist should be no more than half your height. You can find out how to calculate your waist-to-height ratio in our section on what is a healthy weight.

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