Obesity is when a person is carrying too much body fat for their height and sex. A person is considered obese if they have a Body Mass Index (BMI) - weight in kilograms divided by their height in metres squared - of 30 or greater. Obesity can happen when you eat more calories than you burn off over a period of time.
The rate at which you burn off calories from food and drink is known as your metabolic rate. This is often faster during growth spurts and
puberty, but reaches a fairly steady rate by adulthood. People who are very active generally have a higher metabolic rate than those who
are inactive because they burn off calories faster through energetic activity. For example, a labourer working on a building site may need
as many as 4,000 - 5,000 calories a day to keep an even weight. In contrast, an office worker who uses a car to get to work, and does
not exercise, may only need 1,500 calories a day.
If the amount of calories provided by your daily food intake is more than the calories that you burn off, your body will store the extra energy as fat. This is the body's way of protecting itself in case of starvation. However, starvation in developed countries is extremely rare, and this insurance against 'hard times' is hardly ever needed.
Most of us have more food than we need, and much of it is higher in calories than the human body was originally designed to cope with. Fast foods, high calorie snacks, and large portions all mean it is easy to take in more energy than we need. Obesity has now become one of the most serious medical problems of the western world.
Obesity can be measured in different ways. An easy way is to simply step on the scales and compare your actual weight with your ideal weight. Any health or diet book will give this information.
The most scientific way to measure your weight is to calculate your Body Mass Index (BMI). This is your weight in kilograms divided by your height in metres squared (see the 'diagnosis' section on how to work out your BMI). In the UK, people with a BMI between 25 and 30 are categorised as overweight, and those with an index above 30 are categorised as obese. People with a BMI of 40 or more are described as morbidly obese.
Your BMI, waist circumference, and ethnic group, may all help your GP, or practice nurse, to assess your risk of developing obesity-related health problems, such as heart disease. Most modern gyms, and some weighing scales, can electronically measure the percentage of your body weight that is fat, and can compare this with what would be ideal for you, depending on your height, age and sex.
Obesity is fast becoming the developed world's biggest health problem, with over 9,000 deaths a year in England being caused by obesity alone. Adult obesity rates have almost quadrupled over the last 25 years, and two thirds of UK adults are now considered overweight or obese. Of these, 22% of men and 23% of women are obese. This means that they are at least two to three stone overweight and putting their health at serious risk.
According to figures from the National Audit Office, being obese can take up to nine years off your lifespan. It also makes you far more likely to develop a range of health-related problems, including:
- heart disease
- high blood pressure
Combined with a lack of exercise, obesity contributes to one third of cancers of the colon, breast, kidney and stomach.
Being a little bit overweight tends not to cause too many noticeable problems, but once you are carrying a few extra stones, symptoms will affect your daily life. Day-to-day, obesity causes problems, such as shortness of breath. However, the long-term health risks that you cannot see are far more serious, such as heart-related illnesses.
The immediate symptoms of obesity include:
- sweating a lot
- difficulty sleeping
- inability to cope with sudden physical activity
- feeling very tired every day
- back and joint pains
In the longer term, obesity greatly increases your risk of:
- high blood pressure
- heart disease and stroke
- high cholesterol levels (fatty deposits blocking up your arteries)
- breast cancer in women
- gall bladder disease
- gastro-oesophageal reflux disease (when acid from the stomach flows up into the gullet) and associated problems
- arthritis of the back, hips, knees and ankles
- diabetes, and difficulty controlling existing diabetes
- polycystic ovarian syndrome (PCOS - multiple cysts within the ovaries)
- reduced life expectancy
In addition to the immediate and short-term problems of obesity, many people may also experience psychological problems, such as:
- having low self-esteem (self-worth) - or poor self image
- having low confidence levels
- feeling isolated in society
- having reduced mobility leading to a poor quality of life
Obesity does not just happen overnight - it develops gradually from poor diet and lifestyle choices and, to some extent, from your genes.
Lifestyle choices are an important factor in influencing your weight. Eating more calories than you need may be down to poor food choices - for example, eating high fat, processed, or fast food - rather than filling up on fruit, vegetables and unrefined carbohydrates, such as wholemeal bread and brown rice. Alcohol also contains a lot of calories, and heavy drinkers are often overweight.
Bad eating habits also tend to run in families - rather than inheriting a slow metabolism, the habits learned from your parents can be an important factor. Childhood obesity is a strong indicator of weight-related health problems in later life, showing that learned unhealthy lifestyle choices continue into adulthood.
Lack of physical activity
Lack of physical activity is another important factor that is related to obesity. Many of us have jobs that involve sitting at a desk for most of the day, and we rely heavily on our cars to get around. When it is time to relax, we tend to watch TV, or play computer games, and rarely take any regular exercise. If we are not active enough to use up the energy provided by food, the extra calories are stored as fat instead.
Some people tend to stay the same weight for years without much effort, whereas others find they put on weight quickly if they are not careful. This could be due in part to your genes - scientists have discovered certain genes that make you feel hungrier, or make it take longer for you to feel full.
In less than one out of every 100 cases, there is a medical reason for obesity. Conditions such as Cushing's syndrome (over-production of steroid hormones in the body) and an under-active thyroid gland are rare causes of weight gain. Certain medicines, including some steroids and antidepressants, can contribute to weight gain. Also, taking the contraceptive pill and quitting smoking may increase your appetite.
Body Mass Index (BMI) is currently used as the most accurate and reliable way of measuring how overweight you are.
You can work out your own BMI using this calculation:
- measure your height in metres and multiply the number by itself - this is the squared figure
- measure your weight in kilograms
- divide your weight by the answer you got in step 1 (squared height)
- the number you are left with is your BMI
For example, if you are:
- 1.65 metres tall (165cm - 65 inches), your squared figure is 2.72
- 58kg in weight
- 58kg divided by 2.72 = 21.3
- therefore your BMI is 21.3
For most people, an ideal BMI is between 20 and 25.
The best way of tackling obesity is to reduce the amount of calories that you eat and exercise more. Any treatment for obesity is aimed at losing the weight to improve your general quality of life, both physically and psychologically (see the 'symptoms' section). This can include increasing your mobility, or helping to improve your self-esteem (self-worth).
Using the food diary technique you can cut out 500 calories per day from what you are eating. Keeping a diary may help to reveal particular times when you overeat, or certain types of food that you are more inclined to binge on.
Try to find other activities to do rather than snacking, such as reading a magazine. Also, be careful not to buy foods that will tempt you, such as high calorie snacks, as this is an obvious way to cut out 500 calories. You should find that you are still able to enjoy a wide range of tasty options, but in moderation (restraining yourself and avoiding excess).
Avoid special diets. Try to change your eating habits for the long term, choosing a healthy balanced diet instead of cutting out particular food groups. For more information on healthy eating see the 'prevention' section.
Increase your exercise
Increase the amount of aerobic exercise you do. You should aim to do a minimum of 30 minutes of moderate intensity exercise on at least five days a week (or more). This can be done in one session, or split into a number of sessions lasting at least 10 minutes. Before starting an exercise programme, you should first seek advice from your GP because some people may not be able to manage this amount of exercise, while others may benefit from doing more.
When choosing a type of exercise, try to pick an activity that you enjoy, such as swimming or gardening. Aim to increase your heart rate so that you break into a light sweat, and are out of breath by the end of the activity. Check with your GP that any planned activity is safe for you.
Control your weight loss
Do not aim to lose weight too quickly, or you could end up losing muscle rather than fat. Aim for half to 1 kg (1 - 2 lbs) per week. This means eating 500 - 1,000 fewer calories than you were eating and drinking before. You should lose 6 - 12 kg if you keep this up for three months.
Losing weight and keeping it off is a long-term commitment. It is not easy, and it is important not to be disappointed with any minor increases along the way. It is better to look at the overall progress, and remember that any weight loss will improve your health.
Always eat three meals a day, especially breakfast. Do not skip meals, as this will only make you feel hungrier, and it is likely you will overeat at your next meal time. If you are on a calorie controlled diet, remember to reduce your alcohol intake as well.
Medication for obesity is only available in extreme cases from your GP. You need to show you can lose weight on a calorie controlled diet before it is considered. Medication is normally one part of a weight-loss programme, and requires a long term change in lifestyle for lasting results.
The part of the brain that controls how hungry we are is called the hypothalamus. It controls the hormones and chemical signals circulating in our blood that influence appetite. Traditional weight-loss drugs contain amphetamine, which is a stimulant that increases the activity of certain brain chemicals. Stimulants increase the amount of noradrenaline and dopamine hormones in your blood, which stops you feeling as hungry. However, they are not suitable for long-term use and can have serious side effects, including high blood pressure, anxiety and restlessness.
Scientists are trying to develop new medications that have fewer side effects by looking at the relationship between your body fat and hunger. Fat produces a hormone called leptin, which makes you feel less hungry.
Your GP may prescribe you with orlistat, which works by blocking the action of body chemicals called enzymes which digest fat. The undigested fat is not absorbed into your body, and is passed out with your faeces (stools). One orlistat capsule is taken with each main meal (a maximum of three capsules a day). You have to have made significant effort to lose weight through diet, exercise or changing your lifestyle before taking it. Even then, it is only prescribed if you have a BMI of 28 or more, and other diseases related to weight, such as diabetes, high blood pressure, or high cholesterol, or a BMI of 30 or more.
Treatment with orlistat must be combined with a low fat diet and other weight loss strategies, such as doing more exercise. Treatment with orlistat should only continue beyond three months if you have lost 5% of body weight, and beyond six months if you have lost at least 10% of body weight.
Side effects of orlistat include fatty smelly stools, urgency to get to the toilet, oily spotting on your underwear, and flatulence. Side effects are much less likely if you stick to a low fat diet. Women taking an oral contraceptive pill are advised to use an additional method of contraception, such as a condom, if they experience severe diarrhoea whilst taking orlistat.
Orlistat is not prescribed to pregnant women, breastfeeding women, and children.
Sibutramine is another type of medication that may be prescribed to help you lose weight. One sibutramine capsule is taken once a day. It affects chemicals in the brain called noradrenaline and serotonin to make you feel fuller, or satisfied with less food. Again, you need to have made considerable effort to lose weight before sibutramine is considered. Even then, it is only prescribed if you have a BMI of 27 or more, and other diseases related to excess weight, such as diabetes, high blood pressure, or high cholesterol, or a BMI of 30 or more.
Sibutramine will only carry on being prescribed if you lose at least 2 kg within four weeks, and 5% of your initial weight within three months of starting treatment. People with high blood pressure, heart disease, peripheral vascular disease (narrowing of blood vessels usually in the legs), arrhythmias (abnormal heart rhythms), or a history of strokes, should not take Sibutramine. Side effects are common (affects 1 in 10 to 1 in 100 people), including constipation, dry mouth, difficulty sleeping, and increased blood pressure.
If either orlistat or sibutramine are prescribed for you, you will also be offered advice, support and counselling about diet, exercise and making lifestyle changes.
People with a BMI of 40 or more are described as morbidly obese. At this stage, the problem can be very hard to treat. Surgery may be considered to restrict the amount of food eaten, or to interrupt the digestive process. Surgery may also be an option for people with a BMI of 35 to 40, who have life-threatening cardiopulmonary problems - for example, severe sleep apnoea (a sleep disorder where a person experiences irregular breathing at night), obesity-related heart disease, or diabetes.
Surgery is not considered unless you have made significant efforts with other weight loss techniques first. Operations are only successful if followed up with long term commitment to lifestyle changes. A surgical procedure known as gastric banding is normally preferred in the treatment of morbidly obese people.
Gastric banding is a surgical procedure that involves fitting a band around the upper part of your stomach. Gastric banding is usually only recommended as a last resort for people who are extremely obese (those with a BMI over 30), and whose weight poses a serious health risk, for example from diabetes or heart disease. Gastric banding helps you lose weight by controlling the amount of food that you eat.
Having a gastric band fitted is not suitable for everyone. If you have a particular condition, for example an illness related to your heart or lungs, your GP and surgeon may feel the procedure is too risky to carry out. Gastric banding is normally considered a cosmetic procedure. Therefore, the NHS will not pay for surgery for cosmetic reasons alone. Gastric banding is only available on the NHS if you meet specific criteria as set out by your local Primary Care Trust (PCT).
The best way to prevent becoming overweight, or obese, is by eating healthily and exercise regularly. As obese children also tend to be obese in later life, it is very important for parents to set the right example to their children from an early age.
Fruit, vegetables and unrefined carbohydrates should make up the bulk of your diet. Choose brown and wholegrain carbohydrates, and be sparing with high-fat additions, such as cheese, cream and butter. Aim for five portions of fruit and vegetables a day, and vary the type to get the maximum vitamins possible.
Think about how you prepare food - steaming and grilling are healthier ways of cooking than frying and roasting. Go easy on the amount of butter and oil you add during and after cooking. Try not to overeat - listen to your body and stop when you are full. It can take up to 30 minutes for the stomach to register it is full, so eat slowly and wait before tucking into seconds. Serve food in the kitchen, not from the table where you might be tempted to go back for more. Cut down on high fat snacks, junk food and ready meals, as they are often packed with fat, high levels of sugar and salt, and do not fill you up. Dried fruit, oatcakes, yoghurt and fruit are healthier and will keep you feeling full for longer.
Work out your daily calorie requirement from a calorie counting book, and keep a food diary for a week. Do not change anything about your usual diet, but be ruthless in noting down the amount and type of food and drink you have. From this, you can work out how many calories you have consumed compared with the amount you need. As well as showing you whether you need to cut your calories, keeping a food diary can also help you identify the types of food you are eating too much of. As well as recording what you eat, note down the time, place and how you feel. Mood often plays a big part in what we eat - feeling depressed, bored or tired, can quickly lead to comfort eating. Shopping when you are hungry, not making time to prepare a balanced meal, and stress, can also lead to the wrong food choices being made.
It is recommended that, in general, adults should do at least 30 minutes of moderate intensity exercise, at least five days a week (or more). This can be done in one session, or split into a number of sessions lasting at least 10 minutes. However, before starting an exercise programme, it is important to see your GP for advice as some people may not be able to manage this amount of exercise, and others may benefit from doing more exercise.
Exercise does not just burn up calories. Regular, aerobic exercise increases your metabolic rate, so that even when you are not exercising, your body uses more calories overall. However, this effect is quickly lost once regular exercise stops. Regular exercise increases appetite, but having a faster metabolic rate means that any additional calories are easily burnt off, particularly if you make the right food choices as described above.
Exercising when you are overweight can be tough because the extra weight means your body has to work harder. Stick to activities that increase your heart rate and get you sweaty, and slightly out of breath. If you feel embarrassed about joining a gym, try gardening, swimming, or attending fitness classes specifically designed for people who are overweight. In addition, try to fit more activity into your daily routine. Walk or cycle to work, or take the stairs rather than the lift. If you have never exercised before, a brisk 30 minute walk each day is a really good starting point.
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