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Healthy weight for adults


Expert reviewer, Mr Paul McArdle, Registered Dietitian
Next review due July 2023

If you weigh too much or too little, it can increase your risk of several health conditions, including heart disease, diabetes and cancer. It’s a good idea to keep an eye on your weight to make sure you stay within a healthy range.

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

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How does my weight affect my health?

If you’re overweight or obese, it can increase your risk of developing a whole range of health problems. These include conditions such as:


On the other hand, being underweight and not having an adequate diet is associated with:

  • osteoporosis 
  • poor muscle strength
  • reduced immune function – so you're more likely to get infections
  • increased risk of heart problems
  • fertility problems

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

What is a healthy weight?

The most common way of measuring if you're a healthy weight for your height is to calculate your body mass index (BMI). It can also be useful to look at your waist circumference, which gives a better idea of where you store fat on your body. 

BMI (body mass index)

BMI is used to estimate if you're a healthy weight for your height.

You can work out your BMI using our BMI calculator.

BMI is classified as follows.

  • Less than 18.5 = underweight
  • 18.5–24.9 = healthy weight
  • 25–29.9 = overweight
  • 30– 39.9 = obese
  • Over 40 = morbidly obese

As your BMI increases, so does your risk of various diseases.

Limitations of BMI

Knowing your BMI is a simple way to learn more about your weight, but it isn’t perfect. BMI isn't always very accurate in certain groups of people or because of other factors that you need to take into account.

  • Children. Children’s weight changes a lot as they grow. The BMIs of children are usually compared to others in the same age group, to get an idea of whether they’re higher or lower than average.
  • Your personal circumstances. BMI only takes into account your height and weight – not your age, how much exercise you do or your gender. So, it can overestimate a BMI in some people and underestimate it in others. For example, as you get older, proportionally, you lose muscle and gain fat, so that can skew the result.
  • Having a lot of muscle. You may have a very high BMI if you weigh more because you have a lot of muscle, but have very little body fat.
  • Certain ethnic groups including people of Black African, African–Caribbean and Asian descent. In these groups, your risk of health problems such as type 2 diabetes is greater at a lower BMI. Your risk is classed as increased if you have a BMI of 23, and high if your BMI is 27.5.

Body shape and waist circumference

Where you store fat on your body is also an important indicator of whether or not your weight is a risk to your health. Storing fat around your tummy (abdomen) is thought to be worse for your health than storing it around your thighs and bottom.

Your waist circumference gives you a good indication of how much fat you store around your abdomen (tummy).

Here’s how to measure your waist circumference properly.

  • While you’re standing, put a tape measure around your middle. Place it midway between your hipbones and the bottom of your rib cage (usually about level with your belly button).
  • Keep the tape snug around your waist but don’t pull it in.
  • Breathe out and measure your waist.

Here’s how to tell if your waist circumference is putting you at risk of health problems.

Low risk of health problems due to weight

  • Waist circumference in men = less than 94cm (37 inches)
  • Waist circumference in women = less than 80cm (31 inches)

High risk of health problems due to weight

  • Waist circumference in men = 94–102cm (37–40 inches)
    For Asian men, this is 90cm (35 inches) or more
  • Waist circumference in women = 80–88cm (31.5–35 inches)

Very high risk of health problems due to weight

  • Waist circumference in men = more than 102cm (40 inches)
  • Waist circumference in women = more than 88cm (35 inches)

If you’re not sure whether you’re a healthy weight, check with your practice nurse at your GP surgery.

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How to maintain a healthy weight

How much you weigh is mainly determined by the balance between what you eat and drink, and how active you are. The energy that food provides and which you use up when moving or even sitting still is measured in calories. 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. And some medical conditions can also affect your weight. If you're currently over or underweight, you'll need to make some changes to get to your ideal weight.

If you’re overweight or obese

If you're overweight, it will really benefit your health if you try to reach a healthy weight for you. To lose weight, you'll need to use up more calories than you take in. This means reducing how much you eat and drink, as well as increasing how much activity you do.

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 much activity you do. The recommended target to maintain your weight is to do 30 minutes of moderate-intensity activity at least five times a week. You may need to do more than this to lose weight; particularly if you don't reduce the amount you eat enough. 

If you’re underweight

There are lots of reasons why people might be underweight. There could be an underlying medical reason or you may just find it hard taking the time to make healthy, nutritious meals. Being underweight can also be the result of a mental health condition, such as depression and anxiety.

Being underweight means you might not be getting all the nutrients, vitamins and minerals that your body needs to be healthy. Try to increase your calorie intake through eating a balanced and nutritious diet. You might need to eat nutritious snacks in between meals, and take higher fat options (such as full-fat milk) until you reach your ideal weight.

Unexplained weight loss, or inability to put on weight, can sometimes be a symptom of an underlying health problem. If you have concerns about losing weight unintentionally, contact your GP.



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Related information

Tools and calculators

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    • Nutrition support. Oxford handbook of nutrition and dietetics. Oxford Medicine Online. oxfordmedicine.com, published online April 2020
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    • Obesity. Oxford handbook of nutrition and dietetics. Oxford Medicine Online. oxfordmedicine.com, published online April 2020
    • Food labelling, functional foods, nutrigenetics, and nutrigenomics and food supplements. Oxford handbook of nutrition and dietetics. Oxford Medicine Online. oxfordmedicine.com, published online April 2020
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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, July 2020
    Expert reviewer, Mr Paul McArdle, Registered Dietitian 
    Next review due July 2023

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