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Healthy weight for adults Q&As

Published by Bupa's health information team, September 2008.

Answers to questions about healthy weight for adults

This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.

 

How can I calculate my BMI?

Body mass index (BMI) is the measurement often used to work out if someone is underweight, a healthy weight, or overweight. It's calculated using your height (in metres) and your weight (in kilograms).

Explanation

To work out your BMI, divide your weight in kilograms (kg) by your height in metres, and then divide your answer by your height in metres again.

For example, if you're 1.6 metres tall and weigh 65kg, your calculation would be:

  • weight (65) ÷ height (1.6) = 40.625, and then 40.625 ÷ (height) 1.6 = 25.4
  • your BMI is 25.4

To work out your BMI accurately and easily, see our BMI calculator.

If you have a BMI of:

  • less than 18.5 - you're underweight
  • in the range 18.5 to 24.9 - you're a healthy weight
  • in the range 25 to 29.9 - you're overweight
  • in the range 30 to 39.9 - you're obese
  • over 40 -you're morbidly obese (morbidly obese means that the amount you're overweight is harmful to your health)

It's important to remember that BMI doesn't apply to you if you're:

  • pregnant/breastfeeding
  • under the age of 16

If you're in an ethnic minority group, or you're either very muscular or don't have much muscle, your BMI may not be an accurate indicator of how your weight is likely to affect your health. Your GP will be able to tell you if BMI is an appropriate measurement for you.

If you're in any way concerned about your BMI, talk to your GP.

Further information

Sources

  • Simon C, Everitt H, Kendrick T. Oxford Handbook of General Practice. 2nd ed. Oxford: Oxford University Press, 2007:230-231
  • BMI classification. World Health Organization (WHO). www.who.int, accessed 2 June 2008
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I'm pregnant - how much extra should I eat and how much weight should I gain?

There are no set guidelines about how much weight you should put on during pregnancy because all women have very different metabolic rates, put weight on in different places and maintain different levels of physical activity during pregnancy. However, if you were a healthy weight before getting pregnant, you can expect to put on between 10 and 12.5kg (22 to 28lb) during the course of your pregnancy.

Explanation

Pregnancy and body mass index (BMI)

When you first see your midwife after learning you're pregnant (your "booking" appointment), he or she may measure your weight and height and calculate your BMI. If you're underweight or obese at the beginning of your pregnancy, you may need additional care during your pregnancy. This is the only time in your pregnancy that your BMI will be calculated. You won't normally be routinely weighed during your pregnancy unless your midwife has particular cause for concern over your weight.

Weight gain in pregnancy

According to the Department of Health and the Royal College of Midwives, most women gain between 10 and 12.5kg (22 to 28lb) during pregnancy. However, this varies a lot from woman to woman and you may gain more or less than this and still be healthy. If you're concerned that you may be putting on too much or too little weight during your pregnancy, talk to your GP or midwife.

Eating in pregnancy

In general, when you're pregnant you should aim to eat the same healthy diet that you would if you weren't pregnant, making sure you get the right balance of fruit and vegetables, carbohydrates, proteins, dairy products, fats and sugars. Your midwife may advise you to increase your intake of folic acid and iron, which are particularly important for both you and your baby during pregnancy.

When you're pregnant, you don't have to "eat for two". In fact, you don't need to increase the amount of calories you're taking in until the last three months of pregnancy, and even then the Department of Health recommends that most pregnant women only need an extra 200 calories per day. However, if you're expecting more than one baby, or are doing a lot of exercise during your pregnancy, you may need more than 200 extra calories to keep you and your baby healthy: if you do little exercise, you may need fewer. The general advice is to eat according to your appetite, but try to eat more healthy foods and fewer unhealthy foods (for example, replace sugary snacks with fruit). If you're unsure about how much extra you should be eating, talk to your GP or midwife.

Further information

Sources

  • Williamson C. Maternal nutrition guidance: keeping the proportions. Midwives 2006; 9(9):346-349. Royal College of Midwives. www.rcm.org.uk
  • Antenatal care. National Institute for Health and Clinical Excellence (NICE), 2008, 62. p48,50,51. www.nice.org.uk
  • Department of Health. The Pregnancy Book, 2007:8-12. www.dh.gov.uk
  • When you're pregnant. Food Standards Agency. www.eatwell.gov.uk, accessed 6 June 2008
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I'm underweight - how can I gain weight safely?

If your body mass index (BMI) is less than 18.5 you're regarded as being underweight. If you're underweight and not sure if you need to put on weight, talk to your GP.

Explanation

Whether you're trying to gain weight, lose weight or maintain a healthy weight, the important thing is to get the right balance between the amount of energy you take in (eat or drink) and the amount you burn off (physical activity).

If you're trying to gain weight you may want to increase the amounts of carbohydrates (such as pasta, cereals and potatoes) you're eating as these will provide you with more energy. When you're trying to gain weight, you don't want to put on just fat, you also need put on weight in the form of muscle. Eating more protein (found in meats, fish and eggs) will help you do this in combination with the right kinds of exercise.

When trying to put on weight you shouldn't stop exercising. Being physically active is beneficial for your health, and a specific workout may even help you put on weight. If you go to a gym, talk to one of the fitness instructors there who will tell you which kinds of exercises are most suitable for you. He or she may work out an exercise schedule for you. You can also ask your GP what exercise will help you put on weight.

Keep a food and exercise diary - write down everything that you eat and drink and how much/what types of exercise you're doing. This is a good way of finding out:

  • if you're eating too little food
  • whether you're getting a healthy, balanced diet
  • whether you're doing the right kind of/too much exercise

If you're still not sure if your lifestyle is healthy or not, you can show your diary to your GP. He or she will be able to tell you whether you're eating and exercising in a healthy way. If your GP feels that you need to change what you're doing, he or she will either advise you on how to do so or refer you to a dietitian or nutritionist.

If you make these changes to your diet and exercise patterns but are still losing weight or aren't putting any weight on, you should talk to your GP. He or she may want to check whether this is being caused by an underlying health problem (such as hyperthyroidism, type 1 diabetes or infection) which needs to be treated.

Further information

Sources

  • Height/weight chart. Food Standards Agency. www.eatwell.gov.uk, accessed 2 June 2008
  • Sport and exercise. Food Standards Agency. www.eatwell.gov.uk, accessed 9 June 2008
  • Keeping going. British Dietetic Association. www.bdaweightwise.com, accessed 2 June 2008
  • Simon C, Everitt H, Kendrick T. Oxford Handbook of General Practice. 2nd ed. Oxford: Oxford University Press, 2007:297
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Related topics

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This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: September 2008

 

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