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Obesity in adults

Obesity is a condition in which excess body fat affects a person's health. It usually happens because a person eats too many calories (energy) and doesn't do enough physical activity. Obesity increases the risk of a number of health problems including cancer, heart disease and type 2 diabetes.


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.

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.

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.

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.

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.

If you have a BMI of:

  • 23 to 24.9 - you're classed as overweight
  • 25 to 29.9 - you're classed as obese
  • ·over 30 - 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.

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.

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.

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, or counsellor.


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. 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.

Further Information
  • Statistics on obesity, physical activity and diet: England, 2010. The Information, accessed 7 February 2011
  • Background to obesity. National Obesity, accessed 7 February 2011
  • Obesity. Clinical Knowledge, published September 2007
  • Eating well. British Dietetic, accessed 7 February 2011
  • BMI calculator. British Dietetic, accessed 7 February 2011
  • Waist circumference. National Obesity, accessed 7 February 2011
  • R u ready? British Dietetic, accessed 13 May 2011
  • Managing your weight. British Heart, accessed 8 February 2011
  • Simon C, Everitt H, van Dorp F. Oxford handbook of general practice. 3rd ed. Oxford: Oxford University Press, 2010: 180
  • Healthcare professionals. Treatment. National Obesity, accessed 8 February 2011
  • Families. Healthy eating tips. National Obesity, accessed 8 February 2011
  • Options for support. British Dietetic, accessed 13 May 2011
  • Krukowski RA, Smith West D, Harvey-Berino J. Recent advances in internet-delivered, evidence-based weight control programs for adults. J Diabetes Sci Technol 2009; 3(1):184–189
  • The gastric band. Weight Loss, accessed 8 February 2011
  • The gastric bypass. Weight Loss, accessed 8 February 2011
  • Families. What your doctor can offer. National Obesity, accessed 8 February 2011
  • Need to lose weight? British Dietetic, accessed 8 February 2011
  • Start active, stay active: a report on physical activity from the four home countries’ Chief Medical Officers. Department of Health,
  • Keeping going. British Dietetic, accessed 8 February 2011
  • Gastric band. British Obesity Surgery Patients, accessed 8 February 2011

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