Healthy weight for adults

Expert reviewer Mr Paul McArdle, Registered Dietitian
Next review due January 2021

Weighing too much or too little can increase your risk of several diseases, 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 (if you don’t get enough calcium in your diet) 
  • 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

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 so as to get an idea of whether they are higher or lower than average.
  • Having a lot of muscle. You may have a very high BMI if 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. You risk is classed as increased at a BMI of 23, and high at a BMI of 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 abdomen ('apple-shaped') is thought to be worse for your health than storing it around your thighs and bottom ('pear-shaped').

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

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).
  • Make sure the tape measure is horizontal and around your waist.
  • Keep the tape snug around your waist but don’t pull it in.
  • Breathe out and measure your waist.

See 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 walking, running or even sitting still is measured in calories. Put simply:

  • you'll gain weight if you take in more calories than you use up
  • you'll lose weight if you use up more calories than you take in
  • you'll 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 lose the excess weight and maintain a healthy weight. To lose weight, you'll need to burn off more calories through physical activity than you take in from food and drink. This means reducing how much you eat, 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 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.

Read our article Losing weight safely for more tips.

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 conditions 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 go for 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 weight loss, contact your GP.

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Related information

Tools and calculators

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  • Reviewed by Pippa Coulter, Freelance Health Editor, January 2018
    Expert reviewer Mr Paul McArdle, Registered Dietitian
    Next review due January 2021