If you are obese or overweight, you have an increased risk of developing various health problems. A realistic aim for many people is to lose 5-10% of your weight over three months. This is often about 5-10 kg. (10 kg is about one and a half stone.) This modest amount of weight loss will greatly reduce your increased health risks. The best chance of losing weight, and keeping the weight off, is to be committed to a change in lifestyle. This includes eating a healthy diet and doing some regular physical activity.

Are you obese or overweight?

Body mass index

Your body mass index (BMI) is a good estimate of how much of your body is made up of fat. It relates your weight to your height. You can work out your BMI by dividing your weight (in kilograms) by the square of your height (in metres).

So, for example, if you weigh 70 kg and are 1.75 metres tall, your BMI is 70 / 1.75 x 1.75, which is 22.9. Alternatively, your practice nurse can measure and weigh you, and tell you your BMI.

BMI	Classed As	Health Risk
Less than 18.5	Underweight	Some health risk
18.5 to 24.9	Ideal	Normal
25 to 29.9	Overweight	Moderate health risk
30 to 39.9	Obese	High health risk
40 and over	Very obese	Very high health risk

Waist size

Your increased health risk is greater when the extra fat is mainly around your waist ('apple shaped'), rather than mainly on your hips and thighs ('pear shaped'). As a rule, a waist measurement of 102 cm or above for men (92 cm for Asian men) and 88 cm or above for women (78 cm for Asian women) is a significant health risk.

In short, the heavier you are, the longer your carry the extra weight, and the more the fat is around your waist, the greater your health risk.

How common is obesity and overweight?

More than half the adults in the UK are heavier than recommended. About 2 in 5 adults are overweight, and about a further 1 in 5 are obese. The number of obese people in the UK is rising, particularly among young adults. Since 1980, the number of obese adults in the UK has nearly tripled. This has been called the 'obesity epidemic'.

What are the benefits of losing weight?

It is difficult to measure how much 'quality of life' is improved if you lose some weight. Many people feel better, and have more energy. Some people notice an improvement in their self-esteem.

There are also definite health benefits from losing some weight. Many diseases are more common in obese and overweight people, and you are less likely to develop them if you lose some weight. They include: diabetes, high blood pressure, stroke, heart problems, some types of cancer, arthritis of the back and legs, gallstones, menstrual problems, incontinence of urine, breathing problems, some complications of pregnancy, and depression.

What is more, for most obese or overweight people, much of the health benefits come with losing the first 5-10% of your weight. This is often about 5-10 kg. (10 kg is about one and a half stone.) If you are obese, on average, if you reduce your weight by 10%:

You are much less likely to develop the conditions listed above, such as diabetes.

If you already have high blood pressure, osteoarthritis, or diabetes, these conditions are likely to improve. If you are taking medication for these problems, you may need a reduced dose.

Your chance of dying at any given age is reduced by about 20%. This is mainly because you are less likely to die from heart disease, stroke, diabetes, or obesity related cancers.

What is the cause of being overweight or obese?

In some respects, the cause sounds simple. You put on weight if the amount of energy in the foods and drinks that you eat is greater than the amount of energy that you use. Energy from foods and drinks that you do not use is converted into fat, and stored in the body.

A common wrong belief is to think that if you are overweight or obese, you have a low metabolic rate. (Your metabolic rate or 'metabolism' is the amount of energy that you need to keep your body's functions going.) In fact, if you are obese or overweight you have a normal, or even high, metabolic rate (as you use up more energy carrying the extra weight).

The reasons why 'energy taken in' may not balance 'energy used up', and result in weight gain, include the following.

Food and drink intake

Most people in the UK live where tasty food can be found at almost any time of day or night. Many of the foods that we eat are those with the most energy (fatty and sugary foods). Although our body gives us a feeling of fullness after eating enough (satiety), we can easily ignore this feeling if we are enjoying tasty foods. In short, many people simply eat more than their body needs.

Remember too: alcohol contains a lot of calories, and heavy drinkers are often overweight.

Activity and exercise

Most people in the UK do not do enough physical activity. Less people have jobs which are energetic than previously. The variety of labour saving devices and gadgets in most homes, and the overuse of cars, means that most people need to use-up much less energy compared to previous generations. The average person in the UK watches 26 hours of television per week, and many even more (the 'couch potato' syndrome).

A lack of physical activity by many people is thought to be a major cause of the increase in obesity in recent years.

Inheritance

You are more likely to be obese if one or both of your parents are obese. This may be partly due to learning bad eating habits from overeating parents. However, some people inherit a tendency that makes them prone to overeat. Therefore, for some people, part of the problem is genetic.

It is not fully understood how this 'genetic factor' works. It has something to do with the control of appetite. When we eat, certain hormones and brain chemicals send messages to parts of the brain to say that we have had enough, and to stop eating. In some people, this control of appetite and the feeling of fullness (satiety) may be faulty, or not as good as it is in others.

If you do inherit a tendency to overeat, it is not inevitable that you will become overweight or obese. You can learn about the power of your appetite, ways to resist it, be strict on what you eat, and do some regular physical activity. However, you are likely to struggle more than most people to prevent or overcome weight gain.

Medical problems

Less than 1 in 100 obese people have a 'medical' cause. Conditions such as Cushing's disease and an underactive thyroid are rare causes of weight gain. Some medicines such as steroids, some antidepressants, sulphonylureas and sodium valproate may contribute to weight gain. If you give up smoking, your appetite may increase.

How can I lose weight?

Another leaflet in this series called 'Weight Reduction - How to Lose Weight' provides more details. Below is a brief summary of the principles in losing weight.

Motivation is crucial

No weight-loss plan will work unless you have a serious desire to lose weight. You may not feel that being overweight or obese is a problem to you, and have little motivation or desire to lose weight. That is fine, so long as you understand the health risks.

Current food intake

It is helpful to know exactly how much you currently eat. An estimate is often inaccurate. Therefore, a detailed diary of every amount of food and drink that you have over an average week is more helpful. You can discuss this with a nurse or dietician. The number of calories that you eat in a typical week can then be calculated. The simple fact is that, to lose weight, you must eat less than your current food intake.

Eat a healthy balanced diet

Another leaflet in this series called 'Healthy Eating' gives more details. Briefly a healthy diet means:

• AT LEAST five portions of a variety of fruit and vegetables per day.
• THE BULK OF MOST MEALS should be starch-based foods (such as cereals, wholegrain bread, potatoes, rice, pasta), plus fruit and vegetables.
• NOT MUCH fatty food such as fatty meats, cheeses, full-cream milk, fried food, butter, etc. Use low fat, mono-, or poly-unsaturated spreads.
• INCLUDE 2-3 portions of fish per week. At least one of which should be 'oily' (such as herring, mackerel, sardines, kippers, pilchards, salmon, or fresh tuna).
• If you eat meat it is best to eat lean meat, or poultry such as chicken.
• If you do fry, choose a vegetable oil such as sunflower, rapeseed or olive oil.
• Try not to add salt to food, and avoid foods that are salty.

It is best to eat three healthy meals each day, including breakfast. Eat each meal slowly. Don't skip meals. Skipping meals will just make you feel more hungry, make you think more about food, and you are more likely to overeat in the evening. Do not snack between meals. Cut back on alcohol if you drink a lot.

Physical actvity

If you are able, aim to do at least 60-90 minutes of moderate physical activity on at least five days a week. (All adults should aim for at least 30 minutes on five days a week. However, 60-90 minutes is recommended if you are overweight or obese and are aiming to lose weight.) Moderate physical activity includes: brisk walking, jogging, dancing, swimming, badminton, tennis, etc. In addition, try to do more in your daily routines. For example, use stairs instead of lifts, walk or cycle to work or school, etc. See separate leaflet called 'Physical Activity for Health' for details.

Be realistic

Some people aim to get down to a 'perfect' weight. However, if this target is too low, you may become fed up about poor progress, and give up. As mentioned, in most cases most health benefits come from losing the first 5-10% of your weight (often about 5-10 kg). Also, to diet for 3-4 months is the most that many people can manage. It is difficult to remain motivated after this. To lose 5 kg is considered good. To lose 10 kg is excellent. (10 kg is about one and a half stone.)

Lose weight gradually

It is best not to lose weight too fast. If you lose more than a kilogram per week, you may lose muscle tissue rather than fat. It is best to lose an average of ½-1 kg per week (about 1-2 lb per week). To do this you need to eat 500-1000 calories per day less than you did before your diet. You will lose 6-12 kg if you keep this up for three months. Don't be disheartened by minor increases or levelling off in weight for a few days. Look for the overall trend over several months.

Depression or other mental health problems

These may cause you to eat for comfort, or to binge eat. This may lead to weight gain, which may make you more depressed, and so on. See a doctor if you feel that you have depression or another mental health problem. Treatment often helps.

Other general points

The first kilogram is the easiest to lose. This is because you lose water from your body at first as well as fat. It is important to be aware that the initial kilogram or so may seem to fall off, but then the weight loss commonly slows down. Regular weighing, advice, and encouragement by a nurse or dietician is often helpful.

Special diets which are often advertised are not usually helpful. This is because after losing weight, if your old eating habits remain, the weight often goes straight back on. It is usually not a special diet that is needed, but changing to a normal healthy balanced diet - for good.

Medical treatments

Medicines to help with weight loss are an option in some cases. They may help, but they are not wonder-drugs, and you still need to eat less. Doctors are given guidelines on when to prescribe these medicines.

Counselling is sometimes useful, but may not be available in all areas. This may be done 'one-to-one', or in a group setting. The kind of topics discussed may include:

• how to choose meals that are lower in fat and calories.
• how to recognise and resist cues that may make you want to eat when you are not hungry.
• tips on how to reduce the number and size of meals.
• how to eat more slowly.
• how to separate eating from other activities, such as eating in front of the TV.

Surgery is an option if you are very obese. Results are usually good.

Keeping the weight off

Many people lose weight but, at the end of the 'diet', the weight goes back on. To keep the weight off, it is vital that you have a permanent change in your attitudes and lifestyle. This usually means

• keeping to a healthy diet.
• exercising regularly, if possible.
• possibly, a change for the whole household. It is difficult for one member of a household to shop and eat differently to the rest. It is best that the whole household eat a healthy diet.

It does not mean less enjoyment of food. However, it may take a while to learn to enjoy different foods, meals, and recipes.

Some people need more support to keep to a reduced weight than when they were actually dieting and losing weight. A local support group may be useful for this.