Obesity

On this page

Overview

The term obese describes a person who has excess body fat.

In the UK it's estimated that around 1 in every 4 adults and around 1 in every 5 children aged 10 to 11 are living with obesity.

How to tell if you're living with obesity

The most widely used method to check if you're a healthy weight is body mass index (BMI).

Body mass index (BMI)

BMI is a measure of whether you're a healthy weight for your height. You can use the NHS BMI healthy weight calculator to find out your BMI.

For most adults, if your BMI is:

  • below 18.5 – you're in the underweight range
  • 18.5 to 24.9 – you're in the healthy weight range
  • 25 to 29.9 – you're in the overweight range
  • 30 to 39.9 – you're in the obese range
  • 40 or above – you're in the severely obese range

If you have an Asian, Chinese, Middle Eastern, Black African or African-Caribbean family background you'll need to use a lower BMI score to measure overweight and obesity:

  • 23 to 27.4 – you're in the overweight range
  • 27.5 or above – you're in the obese range

BMI score has some limitations because it measures whether a person is carrying too much weight but not too much fat. For example, people who are very muscular, like professional sportspeople, can have a high BMI without much fat.

But for most people, BMI is a useful indication of whether they're a healthy weight.

Waist to height ratio

Another measure of excess fat is waist to height ratio, which can be used as an additional measure in adults who have a BMI under 35.

To calculate your waist to height ratio:

  • Find the middle point between your lowest rib and your hip bone. This should be roughly level with your belly button.
  • Wrap the tape measure around this middle point, breathing naturally and not holding your tummy in.
  • Take your measurement and divide it by your height, measured in the same units (for example, centimetres or inches).

For example, if your waist is 80cm and you are 160cm tall, you would calculate your result like this: 80 divided by 160, which equals 0.5.

A waist to height ratio of 0.5 or higher means you may have increased health risks.

Risks of living with obesity

Obesity is a serious health concern that increases the risk of many other health conditions.

These include:

Living with overweight and obesity can also affect your quality of life and contribute to mental health problems, such as depression, and can also affect self-esteem.

Causes of obesity

Obesity is a complex issue with many causes. Obesity and overweight is caused when extra calories, particularly those from foods high in fat and sugar, are stored in the body as fat.

Obesity is an increasingly common problem because the environment we live in makes it difficult for many people to eat healthily and do enough physical activity.

Genetics can also be a cause of obesity for some people. Your genes can affect how your body uses food and stores fat.

There are also some underlying health conditions that can occasionally contribute to weight gain, such as an underactive thyroid gland (hypothyroidism), although these types of conditions do not usually cause weight problems if they're effectively controlled with medicines.

Some medicines can also make people more likely to put on weight, including steroids and some medicines for high blood pressure, diabetes or mental health conditions.

Treating obesity

The best way to treat obesity is to eat a healthy reduced-calorie diet and exercise regularly.

To do this, you can:

  • eat a balanced calorie-controlled diet as recommended by a GP or weight loss management health professional (such as a dietitian)
  • take up activities such as fast walking, jogging, swimming or tennis for 150 to 300 minutes (2.5 to 5 hours) a week

You may benefit from joining a local weight management programme with group meetings or online support. Your GP can tell you about these.

You may also benefit from receiving support and counselling from a trained healthcare professional to help you better understand your relationship with food and develop different eating habits.

If you're living with obesity and lifestyle and behavioural changes alone do not help you lose weight, a medicine called orlistat may be recommended.

If taken correctly, this medicine works by reducing the amount of fat you absorb during digestion. Your GP will know whether orlistat is suitable for you.

A specialist may prescribe other medicines called liraglutide or semaglutide. They work by making you feel fuller and less hungry.

For some people living with obesity, a specialist may recommend weight loss surgery.

Other obesity-related problems

Living with obesity can cause a number of further problems, including difficulties with daily activities and serious health conditions.

Day-to-day problems related to obesity include:

  • breathlessness
  • increased sweating
  • snoring
  • difficulty doing physical activity
  • often feeling very tired
  • joint and back pain
  • low confidence and self-esteem
  • feeling isolated

The psychological problems associated with living with obesity can also affect your relationships with family and friends, and may lead to depression.

Serious health conditions

Living with obesity can also increase your risk of developing many potentially serious health conditions, including:

Obesity reduces life expectancy by an average of 3 to 10 years, depending on how severe it is.

Outlook

Managing a complex issue like obesity can be hard. Losing weight takes time and commitment.

The healthcare professionals involved with your care can provide encouragement and advice about how to mange your weight, build healthy lifestyle habits and maintain weight loss achieved.

Completing a weight management programme, regularly monitoring your weight, setting realistic goals, and involving your friends and family with ways to lose weight can also help.

It's important to remember that losing what seems like a small amount of weight, such as 3% or more of your original body weight, and maintaining this for life, can significantly reduce your risk of developing obesity-related complications like diabetes and heart disease.

Causes

Obesity is a complex issue with many causes. It's caused when extra calories are stored in the body as fat.

If you consume high amounts of energy, particularly found in high fat and high sugar foods, and do not use all of the energy through physical activity, much of the extra energy will be stored in the body as fat.

Calories

The energy value of food is measured in units called calories. The average physically active man needs about 2,500 calories a day to maintain a healthy weight, and the average physically active woman needs about 2,000 calories a day.

This amount of calories may sound high, but it can be easy to reach if you eat certain types of food. For example, eating a large takeaway hamburger, fries and a milkshake can total 1,500 calories – and that's just 1 meal.

As well as this, many people do not meet the recommended physical activity levels for adults, so excess calories consumed end up being stored as fat in the body.

Diet

Diet and lifestyle factors contribute to development of obesity and overweight. Some of the most common ones are:

  • eating large amounts of processed or fast food – this is food that's high in fat and sugar
  • drinking too much alcohol – alcohol contains a lot of calories
  • eating out a lot – food cooked in a restaurant may be higher in fat and sugar
  • eating larger portions than you need
  • drinking too many sugary drinks – including soft drinks and fruit juice
  • comfort eating – some people may comfort eat due to many other factors affecting their life such as low self-esteem or low mood

Changes in society have also made it more difficult to have a healthy diet. High calorie food has become cheaper and more convenient, and is heavily advertised and promoted.

Physical activity

Lack of physical activity is another important factor related to obesity. Many people have jobs that involve sitting at a desk for most of the day. They also rely on their cars, rather than walking or cycling.

For relaxation, many people tend to watch TV, browse the internet or play computer games, and rarely take regular exercise.

If you are not active enough, you do not use the energy provided by the food you eat, and the extra energy you consume is stored by the body as fat.

The Department of Health and Social Care recommends that adults do at least 150 minutes of moderate-intensity aerobic activity, such as cycling or fast walking, every week. This does not need to be done all in a single session, but can be broken down into smaller periods. For example, you could exercise for 30 minutes a day for 5 days a week.

If you're living with obesity and trying to lose weight, you may need to do more exercise than this. It may help to start off slowly and gradually increase the amount of exercise you do each week.

Genetics

There are some genes associated with obesity and overweight. In some people, genes can affect how their bodies change food into energy and store fat. Genes can also affect people's lifestyle choices.

There are also some rare genetic conditions that can cause obesity, such as Prader-Willi syndrome.

Certain genetic traits inherited from your parents – such as having a large appetite – may make losing weight more difficult, but they do not make it impossible.

In many cases, obesity is more to do with environmental factors, such as not having easy access to healthy food, or unhealthy eating habits learned during childhood.

Medical reasons

In some cases, underlying medical conditions may contribute to weight gain. These include:

However, if conditions such as these are properly diagnosed and treated, they should pose less of a barrier to weight loss.

Certain medicines, including some steroids, medications for epilepsy and diabetes, and some medications used to treat mental illness – including some antidepressants and medicines for schizophrenia – can contribute to weight gain.

Weight gain can sometimes be a side effect of stopping smoking.

Diagnosis

Body mass index (BMI) is widely used as a simple and reliable way of finding out whether a person is a healthy weight for their height.

For most adults, having a BMI of 18.5 to 24.9 is considered to be a healthy weight. A BMI of 25 to 29.9 is considered to be overweight, and a BMI over 30 is considered to be obese.

While BMI is a useful measurement for most people, it's not accurate for everyone.

For example, the normal BMI scores may not be accurate if you're very muscular because muscle can add extra kilos, resulting in a high BMI when you are not an unhealthy weight. In such cases, your waist circumference may be a better guide.

What's considered a healthy BMI is also influenced by your ethnic background. The scores mentioned above generally apply to people with a white background. If you have an ethnic minority background, the threshold for being considered overweight or obese may be lower because you may be at risk of getting conditions such as type 2 diabetes at a lower BMI.

Find out what your body mass index (BMI) is by using our BMI calculator.

Although the BMI calculator can be used to work out your child's BMI, you should speak to your GP if you're concerned about your child's weight.

Visiting your GP

If you're living with overweight or obesity, visit your GP for advice about losing weight safely and to find out whether you have an increased risk of health problems.

Your GP may ask about:

  • your lifestyle – particularly your diet and how much physical activity you do; they'll also ask you whether you smoke and how much alcohol you drink
  • any possible underlying causes for your obesity – for example, if you're taking medication or have a medical condition that may contribute to weight gain
  • how you feel about your weight – for example, if it makes you feel depressed or low
  • how motivated you are to lose weight
  • your family history – as obesity and other health conditions, such as diabetes, are often more common in families

As well as calculating your BMI, your GP may also carry out tests to determine whether you're at increased risk of developing health complications because of your weight.

These could include measuring your:

  • blood pressure
  • glucose (sugar) and cholesterol levels in a blood sample
  • waist circumference (the distance around your waist)

People with very large waists – generally, 94cm or more in men and 80cm or more in women – are more likely to develop obesity-related health problems.

Your GP may also take your ethnicity into account because it can affect your risk of developing certain conditions. For example, some people of Asian, African or African-Caribbean ethnicity may be at increased risk of high blood pressure (hypertension). Healthy waist measurements can also be different for people from different ethnic backgrounds.

After your assessment, you'll be offered an appointment to discuss the results in more detail, ask any questions that you have, and fully explore the treatment options available to you.

Treatment

If you're living with obesity, your GP can offer you for advice about improving your lifestyle and losing and managing your weight safely.

Your GP can advise you about losing weight safely by eating a healthy, balanced diet and regular physical activity.

They can also let you know about other useful services, such as:

  • local weight loss groups – these could be provided by your local authority, the NHS, or commercial services you may have to pay for
  • exercise on prescription – where you're referred to a local active health team for a number of sessions under the supervision of a qualified trainer

If you have underlying problems associated with obesity, such as polycystic ovary syndrome (PCOS), high blood pressure, diabetes or sleep apnoea, your GP may recommend further tests or specific treatment. In some cases, they may refer you to a specialist.

Self-refer for help with your weight

If you need help managing your weight, you might be able to refer yourself directly to services that can help you, without seeing a GP.

To find out if there are any services in your area:

  • ask the reception staff at your GP surgery
  • check your GP surgery’s website
  • search online for NHS weight management services near you

Diet

There's no single rule that applies to everyone, but to lose weight at a safe and sustainable rate of 0.5 to 1kg a week, most people are advised to reduce their energy intake by 600 calories a day.

For most men, this will mean consuming no more than 1,900 calories a day, and for most women, no more than 1,400 calories a day.

The best way to achieve this is to swap unhealthy and high-energy food choices – such as fast food, processed food and sugary drinks (including alcohol) – for healthier choices.

A healthy diet should consist of:

  • plenty of fruit and vegetables
  • meals based on potatoes, bread, rice, pasta and other starchy foods (ideally you should choose high fibre and wholegrain varieties)
  • some milk and dairy foods or dairy alternatives
  • some meat, fish, eggs, beans and other non-dairy sources of protein
  • just small amounts of food and drinks that are high in fat and sugar

Try to avoid foods containing high levels of salt because they can raise your blood pressure, which can be dangerous for people who are already living with obesity.

You'll also need to check calorie information for each type of food and drink you consume to make sure you don't go over your daily limit.

Some restaurants, cafés and fast food outlets provide calorie information per portion, although providing this information isn't compulsory. Be careful when eating out because some foods can quickly take you over the limit, such as burgers, fried chicken, and some curries or Chinese dishes.

Diet programmes and fad diets

Avoid fad diets that recommend unsafe practices, such as fasting (going without food for long periods of time) or cutting out entire food groups. These types of diets do not work, can make you feel ill, and are not sustainable because they do not teach you long-term healthy eating habits.

This is not to say that all commercial diet programmes are unsafe. Many are based on sound medical and scientific principles and can work well for some people.

A responsible diet programme should:

  • educate you about issues such as portion size, making behavioural changes and healthy eating
  • not be overly restrictive in terms of the type of foods you can eat
  • be based on achieving gradual, sustainable weight loss rather than short-term rapid weight loss, which is unlikely to last

Very low calorie diets

A very low calorie diet (VLCD) is where you consume less than 800 calories a day.

These diets can lead to rapid weight loss, but they are not a suitable or safe method for everyone, and they are not routinely recommended for managing obesity.

VLCDs are usually only recommended if you have an obesity-related complication that would benefit from rapid weight loss.

VLCDs should not usually be followed for longer than 12 weeks at a time, and they should only be used under the supervision of a suitably qualified healthcare professional.

Speak to your GP first if you're considering this type of diet.

Exercise

Reducing the amount of calories in your diet will help you lose weight, but maintaining a healthy weight requires physical activity to burn energy.

As well as helping you maintain a healthy weight, physical activity also has wider health benefits. For example, it can help prevent and manage more than 20 conditions, such as reducing the risk of type 2 diabetes by 40%.

The Chief Medical Officers recommend that adults should do a minimum of 150 minutes moderate-intensity activity a week – for example, 5 sessions of 30-minute exercise a week. Something is better than nothing, and doing just 10 minutes of exercise at a time is beneficial.

Moderate-intensity activity is any activity that increases your heart and breathing rate, such as:

  • brisk walking
  • cycling
  • recreational swimming
  • dancing

Alternatively, you could do 75 minutes of vigorous-intensity activity a week, or a combination of moderate and vigorous activity.

During vigorous activity, breathing is very hard, your heart beats rapidly and you may be unable to hold a conversation. Examples include:

  • running
  • most competitive sports
  • circuit training

You should also do strength exercises and balance training 2 days a week. This could be in the form of a gym workout, carrying shopping bags, or doing an activity such as tai chi. It's also critical that you break up sitting (sedentary) time by getting up and moving around.

Your GP, weight loss adviser or staff at your local sports centre can help you create a plan suited to your own personal needs and circumstances, with achievable and motivating goals. Start small and build up gradually.

It's also important to find activities you enjoy and want to keep doing. Activities with a social element or exercising with friends or family can help keep you motivated. Make a start today – it's never too late.

You may need to exercise for longer each day to prevent obesity or to avoid regaining weight if you've been obese. To prevent obesity, 45 to 60 minutes of moderate-intensity activity a day is recommended. To avoid regaining weight after being obese, you may need to do 60 to 90 minutes of activity each day.

Your GP or weight loss adviser will be able to advise you further about the type of exercise you should do and for how long taking into account your current fitness level and individual circumstances.

Other useful strategies

Evidence has shown that weight loss can be more successful if it involves other strategies, alongside diet and lifestyle changes. This could include things like:

  • setting realistic weight loss goals – if you're living with obesity, losing just 3% of your original body weight can significantly reduce your risk of developing obesity-related complications
  • eating more slowly and being mindful of what and when you're eating – for example, not being distracted by watching TV
  • avoiding situations where you know you may be tempted to overeat
  • involving your family and friends with your weight loss efforts – they can help to motivate you
  • monitoring your progress – for example, weigh yourself regularly and make a note of your weight in a diary

Getting psychological support from a trained healthcare professional may also help you change the way you think about food and eating. Techniques such as cognitive behavioural therapy (CBT) can be useful.

Avoiding weight regain

It's important to remember that as you lose weight your body needs less food (calories), so after a few months, weight loss slows and levels off, even if you continue to follow a diet.

If you go back to your previous calorie intake once you've lost weight, it's very likely you'll put the weight back on. Increasing physical activity to up to 60 minutes a day and continuing to watch what you eat may help you keep the weight off.

Medicine

Many different types of anti-obesity medicines have been tested in clinical trials, but the only ones that have proved to be safe and effective for use on the NHS for weight management are orlistat, liraglutide and semaglutide.

Never take an anti-obesity medicine if it has not been prescribed to you.

These types of medicines may not be safe for you and could cause serious side effects.

Orlistat

You can only use orlistat if a doctor or pharmacist thinks it's the right medicine for you. Orlistat is available on prescription from your doctor, or you can buy it at a lower dose from a pharmacy. Products available directly from pharmacies are Alli and Orlos, which must be taken under the supervision of a pharmacist.

Orlistat works by preventing around a third of the fat from the food you eat being absorbed. The undigested fat is not absorbed into your body and is passed out with your poo. This will help you avoid gaining weight, and may help you to lose weight.

You'll need to start eating a balanced diet and exercising regularly before beginning treatment with orlistat, and continue this during treatment and after you stop taking orlistat.

When orlistat should be used

Orlistat will usually only be recommended if you've made a significant effort to lose weight through diet, exercise or changing your lifestyle.

Even then, orlistat is only prescribed if you have either:

  • a body mass index (BMI) of 28 or more, and other weight-related conditions, such as high blood pressure or type 2 diabetes
  • a BMI of 30 or more

Orlistat is not usually recommended for pregnant or breastfeeding women.

Before prescribing orlistat, your doctor will discuss the benefits and potential limitations with you, including any potential side effects.

Follow your doctor's advice about how to take it, and the instructions that come with your medicine.

How long to take it for

Treatment with orlistat should only continue beyond 3 months if you've lost 5% of your body weight. It usually starts to affect how you digest fat within 1 to 2 days.

If you have not lost weight after taking orlistat for 3 months, it's unlikely to be an effective treatment for you. Ask your doctor or pharmacist, as you may need to stop your treatment.

Orlistat and other health conditions

If you're taking medicine for another serious health condition, such as type 2 diabetes, high blood pressure or kidney disease, it may be necessary to change the dose of your medicine. Speak to your GP before starting treatment with orlistat.

If you have type 2 diabetes, it may take you longer to lose weight using orlistat, so your target weight loss after 3 months may be slightly lower.

Side effects of orlistat

Common side effects of orlistat include:

  • fatty or oily poo
  • needing the toilet to poo urgently
  • pooing more frequently
  • an oily discharge from your rectum (you may have oily spots on your underwear)
  • farting (flatulence)

You're much less likely to get these side effects if you stick to a low-fat diet.

If you're taking the oral contraceptive pill and you have severe diarrhoea while taking orlistat, use an additional method of contraception, such as a condom. This is because your body may not absorb the contraceptive pill if you have diarrhoea, so it may not be effective. Check the pill packet for advice.

Liraglutide and semaglutide

Liraglutide (also called Saxenda) and semaglutide (also called Wegovy) are weight loss medicines that work by making you feel fuller and less hungry. They're taken as an injection. Your doctor or nurse will show you how to take it.

Liraglutide is taken once a day, and semaglutide is taken once a week.

You can only take liraglutide or semaglutide if they're prescribed for you by a specialist weight management service. A doctor might recommend that you take one of these medicines if diet and exercise changes have not worked on their own.

You'll need to eat a balanced, reduced-calorie diet and exercise regularly while taking liraglutide or semaglutide.

Before prescribing liraglutide or semaglutide, your doctor will talk you through the benefits and limitations, including any side effects you might get.

When liraglutide should be used

Liraglutide is suitable for adults aged up to 75. It is not recommended if you're pregnant or breastfeeding or have certain health conditions, such as liver or kidney problems.

You'll only be prescribed liraglutide if all of these apply:

When semaglutide should be used

You'll only be prescribed semaglutide if you have health problems due to your weight and you have a BMI of either:

  • 35 or more, or 32.5 or more if you're of Asian, Chinese, Middle Eastern, Black African or African-Caribbean origin
  • 30 to 34.9, or 27.5 to 32.4 if you're of Asian, Chinese, Middle Eastern, Black African or African-Caribbean origin, and you meet other criteria to be treated by a specialist weight management service

It's not recommended if you're pregnant or breastfeeding or have certain health conditions.

How long to take liraglutide or semaglutide for

You'll have a review after taking liraglutide for 3 months, or after taking semaglutide for 6 months. You'll then usually only carry on taking the medicine if you've lost at least 5% of your body weight.

You can take semaglutide for a maximum of 2 years.

Surgery

Weight loss surgery, also called bariatric surgery, is sometimes used to treat people with severe obesity.

Bariatric surgery is usually only available on the NHS to treat people with severe obesity who fulfil all of the following criteria:

  • they have a BMI of 40 or more, or between 35 and 39.9 and have a serious health condition that could be improved with weight loss, such as type 2 diabetes or high blood pressure
  • for people from an Asian, Chinese, Middle Eastern, Black African or African-Caribbean origin, bariatric surgery may be considered for people with a BMI of 37.5 or more, or between 32.5 to 37.4 if they also have another health condition that could improve with weight loss
  • 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

People who have been diagnosed with type 2 diabetes in the last 10 years may be considered for a priority assessment for bariatric surgery if both of these apply:

  • they have a BMI of 30 or more, or are of Asian, Chinese, Middle Eastern, Black African or African-Caribbean origin and have a BMI of 27.5 or more
  • they are receiving, or will receive, assessment in a specialist weight management service

Treating obesity in children

Treating children living with obesity usually involves improvements to diet and increasing physical activity using behaviour change strategies.

The amount of calories your child should eat each day will depend on their age and height. Your GP should be able to advise you about a recommended daily limit, and they may also be able to refer you to your local family healthy lifestyle programme.

Children over the age of 5 should ideally get at least 60 minutes of vigorous-intensity exercise a day, such as running or playing football or netball. Sedentary activities, such as watching television and playing computer games, should be restricted.

Referral to a specialist in treating childhood obesity may be recommended if your child develops an obesity-related complication, or there's thought to be an underlying medical condition causing obesity.

The use of orlistat in children is only recommended in exceptional circumstances, such as if a child is severely obese and has an obesity-related complication.

Bariatric surgery isn't generally recommended for children, but may be considered for young people in exceptional circumstances, and if they've achieved, or nearly achieved, physiological maturity.

Further information

For more information about diet and exercise in children, read:



The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website nhs.uk
Last Updated: 12/12/2024 12:51:18