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Obesity – Weight Loss – BMI


What is Obesity?

Overweight and obesity are defined by the WHO (World Health Organisation) as abnormal or excessive fat accumulation that may impair health. The most common way a person’s weight can be classified is by using the body mass index (BMI). BMI is a useful measure of whether you are a healthy weight for your height. It is not a definitive measure as people who are very muscular will find their BMI is high, despite being fit and healthy.  Waist measurement can also indicate whether a person in likely to develop obesity related health problems.

Overweight and obesity has become a worldwide health issue. Between 1975 and 2016, obesity has overall nearly tripled with a greatest increase seen in children ages 5-18. In 2016 the WHO estimated 39% of adults as being overweight with 13% being classed as obese. It was also reported that 18% of children between 5-18 years old were overweight with 6% of girls and 8% of boys being obese.

What are the causes of obesity?

Obesity is generally caused by consuming more calories than the calories you burn. When these calories are not burnt off through exercise it is generally stored in the body as fat.  This imbalance between consumption and what the body uses is commonly blamed on the increase and availability of cheap, convenient, calorie dense foods, which are high in fat and sugar, together with people leading more sedentary lives.

Some medical conditions can contribute to weight gain such as, underactive thyroid gland (hypothyroidism) or Cushing’s syndrome, although proper diagnosis and treatment should help control the amount of weight gain.

Medicines such as some antidepressants and those for treating schizophrenia, epilepsy, diabetes can make weight gain more likely but, with help and advice from your health professional, can be managed.

Sometimes people may blame a difficulty in keeping their weight down as “genetic”, but genetic conditions that contribute to weight gain are very rare.  Some people may have ‘inherited’ a large appetite from their parents and although this may make losing weight more difficult, it is not impossible.  Weight gain is more likely to be down to poor eating habits learnt in childhood and lack of exercise.

 What are the risk factors?

If you are overweight or obesity this can greatly increase your chances of developing potentially life-threatening conditions, such as:-

Other serious health conditions are:-

How is overweight and obesity diagnosed?

Checking your BMI is a good and simple way to check whether you are a healthy weight for your height. The BMI ranges are set out as follows:-

18.5 – 24.9 is considered a healthy weight

25 – 29.9 is considered overweight

30 – 39.9 means you are obese

40+ is severely obese

When calculating a child’s BMI their age is also taken into account.

Follow the link below to calculate your BMI.

A BMI may not always be an accurate measurement so if you are muscular then your waist measurement may be a better indicator.  For men a measurement over 94cm and for women a measurement over 80cm suggests you are more likely develop health issues related to your weight.

A healthy BMI and waist circumference may also be influenced by your ethnic background. The above scores and measurements generally apply to people of a white Caucasian background. For example, the threshold for diagnosing obesity in people of south Asian origin is an BMI of 27.5.

If you are concerned about your weight and wish to seek advice about weight loss and/or related health issues, visit your GP who can also run further tests if necessary.  Additional tests could include blood pressure and glucose and cholesterol levels.  Your GP will ask about your lifestyle (diet, exercise, whether you smoke and/or drink), family history and whether you are taking medication which could contribute to your weight gain. Your GP may also ask how you feel about being overweight and what motivation you have to losing weight. Once your test results are in, you can discuss the treatment options available to you.

What treatment is there for obesity?

Your GP will want to deal with any underlying health problems and if necessary refer you for further tests or specific treatment. They will advise you on how to lose weight safely by eating healthy and with regular exercise. Your GP is likely to discuss with you your attitude towards food and weight loss in order to consider the best treatment.


The best way to treat obesity is to eat a balance, calorie-controlled diet as recommended by your GP.  Trying to change your approach to food and having to reduce or cut out some of your favourite foods can be incredibly difficult. Joining a weight loss group can be of great help when trying to stick with a diet. Regular meetings will enable you to receive regular advice, support and encouragement when you need it. Do not be tempted by fad diets promising quick weight loss through fasting and cutting out entire food groups.  Quite often they can make you ill and do not teach you long term healthy eating habits, so you will very likely put the weight back on. Choose a diet programme which considers gradual sustainable weight loss, proportion size and varied, healthy eating.  In exceptional cases your GP may recommend a very low calorie diet if you have an obesity-related complication this should only be followed under supervision from a qualified professional.

If it is felt you will benefit from psychological support you can be referred to a trained healthcare professional to help you develop a healthier, more positive attitude towards food and eating.


Taking up a more active life style will help you to burn more calories, lose weight and also provide health benefits.  If you haven’t exercised for some time, walking or swimming can get you gently started.  Your GP or weight loss adviser should be able to advise you on how much and the best type of exercise for you, based on your fitness levels.  Choose an activity you think you will enjoy and so more likely to stick with.

The Chief Medical Officers recommend that each week adults should do at least two and a half hours of moderate exercise which increases their heart and breathing rate, or one hour 15 minutes of vigorous activity which should make you breath hard and your heart beat rapidly.  You should also do strength and balance exercises twice a week.


Though there are many medicines or treatments that claim to aid weight loss, only the drug orlistat has been tested in clinical trials and proved to be safe and effective. Orlistat works by preventing a third of the fat from the food you eat being absorbed as moves through the digestive system.  The undigested fat is then excreted in your stools. Together with a balanced diet and an exercise program, which should be started before treatment begins, you should expect to lose weight. After 3 months you will have a review with your GP.  If you haven’t lost 5% or more of your body weight in this time, you will be advised to stop taking orlistat as it will not be considered an effective treatment for you.  If you have lost weight your GP may suggest taking the medication for 12 months or more.

Orlisat is usually only available on prescription and only recommended if your BMI is 28 or more and you have other weight related health issues such as type 2 diabetes or high blood pressure, or you have a BMI over 30.  You will also have already made efforts to lose weight through exercise and diet.


Surgery used to treat obesity is called bariatric surgery.  Surgery would normally only ever be considered to treat those who are severely obese and is only available on the NHS where the following criteria has been fulfilled: –

  • Have a BMI of 40 or more, or between 35-40 and have a serious health issue such as type 2 diabetes or high blood pressure.
  • All appropriate non-surgical measures have been tried but the person hasn’t achieved or maintained adequate, clinically beneficial weight loss.
  • The person is fit enough to have anaesthesia and surgery.
  • The person has been receiving, or will receive, intensive management as part of their treatment.
  • The person commits to the need for long term follow up.
  • In rare cases surgery maybe recommended as a first treatment if your BMI is 50 or over.

How are children with obesity treated?

As when treating adults with obesity, initial treatment will concentrate on improving diet and increasing exercise.  A GP will be able to advise on diet and recommended daily limits.  They may refer you to a local family healthy lifestyle program. For further advice on how to help your child lose weight and get fit, please follow this NHS link.

Your GP may want to refer your child to a specialist if he/she develops an obesity related complication or they believe there is an underlying medical condition causing your child’s weight issues.

Orlistat is rarely recommended and is only likely to be prescribed if a child is severely obese and has an obesity related complication.

Bariatric surgery is only ever recommended in exceptional circumstances and if the child is physically mature.

How can I prevent becoming overweight or obese?

Overweight or obesity is largely preventable.  As an individual people can take steps to prevent excessive weight gain.

  • Eat a healthy and varied diet
  • Limit intake of calorie dense foods containing high levels of fats and sugars, such as fast food, processed food and sugary drinks.
  • Increase intake of fruit, vegetables, whole grains, nuts and seeds,
  • Regularly exercise

Calorie intake should normally be no more than 2500 calories/day for men and 2000 for women.  If you are trying to lose weight most people are advised to reduce their calorie intake by 600 a day to 1900 calories for men and 1400 calories for women.

If you need to lose weight a good way of keeping a check on your calorie intake is by keeping a food journal. Studies have shown that keeping a food journal doubles your chances of losing weight.  If you don’t like the idea of taking a note book with you everywhere you go, there are also apps, such as MyFitnessPal, which can help you keep a track of your calorie intake and record the exercise you take.

It is quite often difficult to get motivated to exercise, especially if you’ve never really enjoyed taking part in physical activities.  Find something you think you might enjoy, whether it’s walking, swimming, cycling or dancing, there are a lot of clubs and classes around.  Ask a friend or family member to exercise with you. You are more likely to continue with a class or activity if you can mutually support and encourage each other.  Make enquiries at your local library and leisure/sports centre about what is going on locally.  If you are interested in taking up running but are a complete beginner, you may like to click on the following link and check out the NHS couch to 5K running plan.