Obesity in adults

About obesity

If you regularly take in more calories (energy) than you use up, the extra energy is stored in your body as fat. You will start to gain weight and eventually become obese.

The number of obese adults in the UK has tripled since 1980. In 2008 around seven out of 10 men and six out of 10 women in the UK were either overweight or obese.

Complications of obesity

If you're obese, you're at risk of developing health problems. These include:

  • type 2 diabetes
  • high blood pressure
  • aching joints and osteoarthritis
  • coronary heart disease
  • some types of cancer
  • sleeping problems, such as snoring and sleep apnoea
  • back pain
  • breathlessness

Women who are obese are more likely to have problems during and after pregnancy. If you're obese, it can cause low self-esteem and poor body image.

Causes of obesity

Eating an unhealthy diet and lack of exercise are the main causes of obesity. Fatty foods, sweet foods and sugary drinks can cause weight gain if you eat or drink them often. This is because they contain lots of calories. Large portion sizes can increase your chances of becoming obese.

If you were overweight or obese as a child, or if other people in your family are, you're more likely to be obese as an adult. Genetic factors could play a role in this.

Occasionally medical conditions and medicines can make you put on weight.

Diagnosis of obesity

If you think you're overweight or obese, you should visit your GP. He or she will ask you about your symptoms and may check your weight and height to calculate your body mass index (BMI). This is used to work out if you're a healthy weight for your height. You can calculate your BMI by dividing your weight by your height, then dividing the answer you get by your height again. To work out your BMI, see our BMI calculator.

If you have a BMI of:

  • 25 to 29.9 - you're classed as overweight
  • 30 to 39.9 - you're classed as obese
  • over 40 - you're classed as severely obese

These BMI ranges aren’t appropriate for everyone. For example, if you have a lot of muscle, your BMI may not be an accurate measurement of whether you need to lose weight.

If your BMI is less than 35, your GP may also measure your waist. Carrying extra weight around your middle (an 'apple shape'), rather than your hips and thighs (a 'pear shape'), puts you at higher risk of obesity-related diseases. Your health may be at risk if you're a man with a waist measurement of 94cm (37 inches) or more, or a woman with a waist measurement of 80cm (32 inches) or more.

For certain ethnic groups, for example people of Asian descent, waist size is a better measure of the obesity-related health risks than BMI.

Your GP may measure your blood pressure and offer a blood test to check your cholesterol and blood sugar levels. If you have health problems related to obesity, your GP will provide the treatment you need.

Treatment of obesity

Losing weight takes time and effort so think about why you want to lose weight and whether you’re ready to make changes.

If you have decided that you’re ready to change, the best way to achieve a healthy weight is to improve your diet and eating habits. At the same time you need to increase the amount of physical activity you do.

You're more likely to keep the weight off for good if you lose weight slowly. This allows time for new, healthier eating habits to become part of your everyday life. It's important that you're realistic about the amount of weight you want to lose. The recommended rate of weight loss is 0.5 to 1kg (1 to 2 lbs) per week.

A healthy, balanced diet

It's important that you follow a balanced diet and control portion size to maintain a healthy weight.

  • Base your meals on starchy foods such as potatoes, pasta, bread and rice. You should choose wholegrain varieties if you can.
  • Try to limit the amount of food high in fat and sugar, such as cakes, biscuits and butter. You should cut off any visible fat on meat and choose lean options.
  • Introduce more fruit and vegetables into your diet so that you eat at least five portions a day. You could snack on fruit during the day and have a portion of vegetables with your evening meal.
  • Aim for at least two portions of fish a week, including one of oily fish such as salmon, mackerel, or fresh tuna.
  • Alcohol is high in calories and increases your appetite, so reducing the amount you drink can help control your weight.
  • Water is the best drink. You could try flavouring water with low-calorie squash or ice and lemon. Remember that fizzy drinks contain lots of sugar.
  • It's fine to snack, but choose healthy options such as fruit and low-fat yoghurts. Snacking can help you manage your appetite so that you eat smaller portions at main meals.

Fad diets

A fad diet involves eating a very limited range of foods. These diets aren't healthy and although they may lead to short-term weight loss, you will always put the weight back on as soon as you return to your usual diet. There is no quick fix for losing weight.

Commercial weight-loss programmes

There are several commercial weight-loss programmes that can help you manage your weight. Slimming clubs are useful for people who like group meetings and prefer weekly support.

There are a range of online diet programmes available, which can help you lose weight and maintain your weight loss. These may be more suitable if you’re too busy to attend a group but you would benefit from social support via web chats and online discussion forums.

Talk to your doctor or practice nurse about which options would best suit your individual needs and fit in with your lifestyle.

Physical activity

You should aim to do some physical activity every day. The recommended healthy level of physical activity 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.

It’s 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.

Moderate means your breathing is faster, your heart rate is increased and you feel warmer. At this level of activity, your heart and lungs are being stimulated and this goes towards making you fitter. You may need professional supervision and if you're unsure about starting to exercise, get advice from your GP.

It's important that you find an activity you enjoy to help you stay motivated. If you find exercise boring on your own, invite a friend to join in with you or join a local club.


If you have been following a healthy diet and increasing your physical activity, but have still not seen any improvement in your weight, your GP may prescribe a medicine called orlistat to help you lose weight. Orlistat stops your body absorbing all the fat from your food. It’s recommended for people with a BMI of 30 or higher. Your GP may prescribe you orlistat if your BMI is 27 or higher and you also have health problems associated with obesity.

Your GP will discuss any potential benefits and limitations of the medicine. You will also be given information about patient support programmes. It’s important that you have regular follow-up appointments with your doctor.

Orlistat is also available over the counter. You need to talk to your pharmacist before he or she will sell it to you.

In January 2010 the European Medicines Agency suggested that the obesity medicine sibutramine (Reductil) may increase the risk of non-fatal heart attacks and strokes. The medicine has now been withdrawn.


Occasionally, surgery is recommended for obesity. The most common types of surgery are gastric bypass and gastric banding. They involve reducing the size of the stomach so that you eat less, or bypassing part of the gut so that your body absorbs less food. Surgery is recommended for people with obesity who:

  • have a BMI of 40 or higher, or have a BMI between 35 and 40 with a disease that could be improved with weight loss (eg diabetes or high blood pressure)
  • have tried other suitable ways of losing weight without any success
  • are fit for surgery
  • commit to a long-term treatment programme

If you have a BMI of 50 or more, surgery may be the first option. If your GP recommends surgery, he or she will refer you to a specialist. The specialist will talk to you in more detail about the benefits and limitations of the surgery. After the operation, you will work with a specialist obesity team who will help you to make changes to your diet.

Can I take orlistat for obesity if I'm pregnant?


No, you shouldn’t take orlistat if you're pregnant or breastfeeding.


There is very little research into the effects of weight-loss medicine and pregnancy. Doctors don’t recommend that you take it when you're pregnant because your growing baby may not receive the right nutrition.

You shouldn’t take orlistat while breastfeeding because doctors don’t know whether or not it passes to your baby in the breast milk.

If you are sexually active, make sure that you use contraception while taking orlistat. If you take the contraceptive pill and you find that orlistat gives you diarrhoea, use additional contraception such as condoms.

If you are planning to have a baby, or you have become pregnant while taking weight loss medicine, talk to your GP or pharmacist.

I'm finding it difficult to change what I eat - is there anyone who can help me?


Yes, talk to your GP if you're having problems improving your diet, or reducing how much you eat. He or she can refer you to a dietitian, nurse, counsellor or local weight-management group.


You may find that a weight-management group or slimming group gives you the advice, support and motivation that you need. Alternatively, there may be a practice nurse who can advise you on diet and exercise, and keep you going with your weight loss.

For some people, a counsellor or psychologist can help by giving individual advice and exploring your emotional relationship with food. He or she can help you find new ways to deal with your feelings.

A registered dietitian can give you advice on all aspects of your diet. He or she must be qualified to university degree level and registered with the Health Professionals Council to use the title dietitian.

It’s best to talk to your GP about your options.

I lose weight but always put it back on. How can I prevent this?


There are a number of things you can do to keep weight off permanently. Eating a healthy, balanced diet and keeping physically active will help you to lose excess weight. You will need to continue these habits to maintain a healthy weight.


It's important that you have a realistic goal for weight loss. You should aim to lose weight slowly and steadily. An achievable weight loss is five to 10 percent of your current weight over a period of six months. This reduces your risk of heart disease, stroke, diabetes and some cancers.

Making small changes to your diet will help to reduce your weight. To lose weight you need to eat fewer calories. It's recommended that you eat about 500 to 600 fewer calories each day to lose 0.5kg per week.

Physical activity combined with healthy eating can help you lose weight and keep it off. Aim to do some physical activity every day. The recommended healthy level of physical activity is 150 minutes (two and a half hours) of moderate exercise over a week in bouts of 10 minutes or more. One way to do this is by carrying out 30 minutes on at least five days each week.

It’s 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.

It can help to weigh yourself regularly to see your progress. Measuring your waist is also helpful. If you weigh yourself every day, you will see your weight going up and down as a result of fluid changes. Therefore, don't weigh yourself more often than once a week.

If you have good support from those close to you, you're more likely to continue with a healthy diet and lifestyle. Talk to your family and friends about the things they can do to help you lose weight.

Once you have reached your target weight, keep up the good habits you have started.

How much weight will I lose with a gastric band?


This will depend on a number of factors including how much physical activity you do and what you eat after surgery.


If you're overweight or obese, you may find it very difficult to lose weight. Your GP may recommend you have surgery. Losing excess weight is very important because it will reduce your risk of health problems including diabetes, heart disease and high blood pressure.

Some people don't lose any weight after a gastric band operation, whereas others lose weight but put most of it back on. However, on average, you will lose around half of the excess fat within two years. After surgery you will need to eat a strict diet. You're more likely to lose weight if you follow this diet, increase your physical activity, regularly attend follow-up appointments with the healthcare team, and keep in contact with a support group.