Healthy weight for adults

There are several different ways of working out whether you are a healthy weight. The most commonly used measurement is body mass index (BMI). Your waist circumference and body shape can also indicate whether you may be at an increased risk of developing health problems.

If you are not sure whether you are a healthy weight, check with a doctor or nurse.

BMI

BMI takes into account your weight and height and is, in general, a good indicator of how much body fat you have.

To find out your BMI, calculate your weight in kilograms divided by the square of your height in metres.

Using this system, if your BMI is:

• less than 18.5, you are underweight
• between 18.5 and 22.9, you are a healthy weight
• between 23 and 24.9, you are overweight
• between 25 and 29.9, you are obese
• over 30, you are morbidly obese

If your BMI is 23 or over, it is a good idea to try to lose excess weight in order to prevent serious health problems from developing. Your health may be already at risk if you have a BMI of 25 or more.

BMI does not apply to everybody, for example, it is not used for pregnant women or children. Children’s weight changes a lot as they grow, so their age and sex are taken into account when working out whether or not they are a healthy weight. BMI cannot be applied to pregnant women as they are gaining weight because of their growing baby.

BMI may also be unsuitable for people with a lot of muscle. For example, athletes and people who play a lot of sport may have a BMI of over 25 but have very little body fat.

If you belong to certain ethnic groups (for example, if you are of Asian descent), the BMI ranges above may not be appropriate for you. Speak to a doctor for more information.

Body shape and waist circumference

Where you store fat on your body is an important indicator of whether or not your weight is a risk to your health – this may be a better measure in people who do a lot of sport. Storing fat around your abdomen (tummy) and waist (apple-shaped) is thought to be worse for your health than storing it around your thighs and bottom (pear-shaped). If you are apple-shaped, you are at a higher risk of developing coronary heart disease, diabetes and high blood pressure (hypertension).

If you are carrying excess fat around your abdomen, it is possible that your waist circumference is greater than is healthy. According to the World Health Organization, men with a waist measurement of 102 cm (40 inches) or more, and women with a waist measurement of 88 cm (34.5 inches) or more, have the greatest risk to their health. Again, these guidelines may vary from country to country.

Your weight is determined to some extent by your genes and how easily you put on weight, but also by the balance between what you eat and drink and how active you are. The energy that your food provides, which you use up walking, running or even sitting still, is measured in calories.

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

But what does this mean for you, and what changes can you make if you weigh too much or too little?

If you are a healthy weight

Aim to maintain your weight through a combination of eating a healthy, balanced diet and doing regular physical activity.

A healthy, balanced diet means basing your meals around starchy foods, preferably wholegrain varieties, eating lots of foods high in fibre and at least five portions of fruit and vegetables a day – aim for these food groups to make up two-thirds of your diet. Try to limit how much you eat of foods that contain lots of fat, sugar and salt. Do not skip meals as your body will respond by storing fat to prevent against starvation. Instead, eat regular meals, especially breakfast, and make sure your portion sizes are appropriate.

Try to do some physical activity every day. The World Health Organization recommends the healthy level of physical activity for adults is 150 minutes (two and a half hours) of moderate exercise over a week in bouts of 10 minutes or more. You can do this by carrying out 30 minutes on at least five days each week. Alternatively, you can do 75 minutes of vigorous intensity activity over the course of a week.

It is important that you include at least two weekly activities to build up muscle strength, such as exercising with weights. Try to spend as little time as possible being inactive.

If you are overweight or obese

Your risk of health problems such as heart disease, diabetes and cancer is higher if you are even a little overweight and the more overweight you are, the greater your risk of these diseases. This risk increases even further if you do not do any physical activity.

Losing excess weight and getting active will be very beneficial for your health. To lose weight, you need to burn off more calories through physical activity than you take in from food and drink. The best way to do this is by increasing how much exercise you do and reducing how much you eat.

Eat a healthy, balanced diet and cut down on foods containing fat and sugar. If you do not exercise, start by building physical activity into your usual daily routine, for example, walking to work instead of driving or taking the stairs instead of the lift. Gradually increase how much you do until you reach the weekly recommendation of 150 minutes.

If you are underweight

There are many reasons why you may be underweight. These include medical conditions, such as anorexia nervosa, in which you have a distorted idea of your body shape and weight, and try to limit how much you eat (or stop eating completely) and over-exercise. You may also be at risk of malnutrition if you have a long-term medical condition such as cancer or chronic obstructive pulmonary disease (COPD). Older people may be underweight through not eating enough, possibly because they find it difficult to prepare or eat meals, or they have a reduced appetite.

If you have a very restricted diet, you may not be getting all the vitamins and minerals that your body needs to be healthy. This can lead to health problems such as heart arrhythmia (palpitations) and osteoporosis. Try to increase your calorie intake through eating a balanced and nutritious diet, in order to gain weight and get back into a healthy weight range for your height. A doctor or a dietitian may give you advice and information about how to do this.

Unexplained weight loss or being unable to put on weight can sometimes be a symptom of an underlying health problem. If you find it difficult to put on weight or if you have lost a lot of weight in a short time, see a doctor.

Further information

• International Obesity Taskforce
  www.iaso.org/iotf
• World Health Organization
  www.who.int

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