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Reviewed by Dr Roger Henderson, GP
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What is obesity?
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| You are apple-shaped if fat is on the stomach. |
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Obesity is more than just a few extra pounds.
Obesity is the heavy accumulation of fat in your body to such a
degree that it rapidly increases your risk of diseases that can damage your
health and knock years off your life, such as heart disease and
diabetes.
The fat may be equally distributed around the body or
concentrated on the stomach (apple-shaped) or the hips and thighs
(pear-shaped).
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Test yourself
Are you apple or pear shaped? Use
to find out.
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For medical purposes, the body mass index (BMI) is used to
determine if your weight is in the healthy range.
Doctors use BMI because it compares your weight against your
height.
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Work out your BMI
Use our
BMI calculator.
Otherwise, take your weight (kg) and divide it by the square
of your height (m).
For example, if you weigh 80kg and are 1.7m:
1. Multiply your height by itself 1.7x1.7=2.89
2. Divide your weight by this figure.
3. 80 ÷ 2.89= 27.7kg/m2.
27.7 is the BMI.
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You are in the normal range if your BMI is between 18.5 and 25
(kg/m2).
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You are overweight if your BMI is between 25 and 30.
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You are obese if your BMI is 30 or higher.
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You are morbidly obese if your BMI is 40 or higher.
How common is obesity?
Around one in four men and one in three women in the UK are
overweight, according to government statistics.
While slightly more women than men are obese (24 per cent versus
23 per cent), in the last ten years there has been a greater increase in the
number of men who are obese.
The Department of Health predicts that if this trend continues,
by 2010 around 6.6 million men will be obese compared to 6 million
women.
Stomach obesity, where weight is concentrated on the tummy, is
the most common type of obesity and affects 30 per cent of adult
men.
Obesity and stomach obesity are rapidly increasing, especially
in young people.
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Children and BMI
The BMI figures used in this article apply to adults
only.
Doctors use special charts to work out BMI for children to
take account of differing rates of growth and development.
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Around one in three children between the ages of 2 and 15 are
overweight. While in total more girls than boys are overweight, a greater
number of boys are obese.
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14 per cent of boys are overweight.
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17 per cent of girls are overweight.
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19 per cent of boys are obese.
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18 per cent of girls are obese.
Government statistics also show that children are more likely to
have a weight problem if one parent is overweight, and this risk is increased
if both parents are overweight or obese.
What problems can obesity cause?
Psychologically, being overweight can affect your body image
and damage self-esteem. In some cases this can cause social anxiety and
depression.
Common physical problems include:
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difficulties breathing
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difficulties walking or running
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increased sweating
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pain in the knees and back
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skin conditions such as acne
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gallstones.
The following medical conditions are also more common in obese
people than in those of normal weight:
These conditions are often known as obesity-related diseases
and are some of the most common causes of death before the age of 75. This is
why obesity increases your risk of mortality.
What causes obesity?
Obesity can be hereditary, so some people are at increased
risk.
Genetic factors can affect appetite, the rate at which you burn
energy (metabolic rate) and how the body stores fat. Examples of genetic
diseases are polycystic ovary syndrome (PCOS) and hypothyroidism.
But even if your genes make weight gain more likely, it is not
inevitable that you will be overweight.
Obesity develops from:
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overeating
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irregular meals
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lack of daily physical activity.
This is why obesity has trebled since 1980, when only 6 per cent
of men and 8 per cent of women were obese. In this time our lifestyles have
changed rapidly, with the ready availability of convenience foods and car
journeys replacing walks to work and school.
It is lifestyle that determines how the genes
develop.
Medicines such as antidepressants, corticosteroids and oral
contraceptives can also cause weight gain.
When is obesity dangerous?
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UK clothes size
For women, the waistline target of 80cm means you should
comfortably fit into a size 16.
Dress size 14 16 18 20
Waist (cm) 79 84 89 95
Dress size 22 24 26
Waist (cm) 101 107 113
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If you have a BMI of more than 25, you should lose weight. The
same is true if you carry too much fat around the middle because this increases
your risk of heart disease and diabetes.
Your waist should be no more than 102cm/40" (men) or 88cm/35"
(women), with stricter targets for Asians of less than 90cm/35" (men) and
80cm/32" (women).
To reduce your risk of cardiovascular disease further, you
should watch your waistline and make sure it's no more than 94cm/37" (men) and
80cm/32" (women).
How is obesity treated?
Initially, your doctor will suggest you
lose weight through a
change in diet and an increase in physical exercise.
Clinical guidelines are to aim for a weight loss of between 5kg
and 10kg (11-22lb) over three months. This equals about 0.5kg or 1lb per
week.
If you are obese, losing this amount will have a positive effect
on your risk of cardiovascular disease and diabetes by reducing blood pressure,
blood sugar (glucose) and cholesterol levels.
A dietitian can help you lose weight by giving nutritional
advice on buying and preparing foods and designing a weight-loss
plan.
Weight-loss plans are usually based on a low-fat diet of between
1500 and 2000 calories a day, which will result in a weight loss of 5 to 10kg
in more than 90 per cent of obese people.
How do diet and exercise help?
Your body needs a certain amount of energy (calories) each
day. Excess energy is stored as fat. The more active you are, the more calories
your body needs.
By eating less than your body needs and exercising more, you
force your body to use its existing fat stores for energy.
By burning excess fat, you lose weight.
When is medical treatment necessary?
Your doctor will usually only consider medicines for weight-loss
if changes to diet and exercise are not effective.
Three medicines for weight-loss are available on the NHS:
orlistat (Xenical),
sibutramine (Reductil) and
rimonabant
(Acomplia).
You will still need to follow a calorie-controlled diet and
start an exercise plan while taking these drugs.
Treatment with Xenical and Reductil will only be continued after
three months if you have lost 5 per cent of your body weight in that
time.
While these medicines can help you to lose weight, there may be
a gradual reversal of any weight loss after you stop treatment. To help avoid
this, you will need to continue with changes to your diet and exercise
levels.
Medicines for obesity are not yet recommended for young people
under the age of 18 because we have no knowledge of possible negative effects
on puberty and later eating behaviour.
Orlistat (Xenical)
Xenical reduces the amount of fat
that is absorbed from the bowels.
Your doctor can prescribe this drug if you are obese, or if
your BMI is higher than 28 and you have a related risk factor such as high
blood pressure, high cholesterol or diabetes.
Common side-effects include headache, urgent or increased need
to open the bowels, flatulence (wind) with discharge, and oily or fatty
stools.
Sibutramine (Reductil)
Reductil acts on chemicals in the
brain called serotonin and noradrenaline to make you feel fuller for
longer.
Your doctor can prescribe this drug if you are obese or have a
BMI higher than 27 with a risk factor for heart disease, and you haven't been
able to lose weight through lifestyle change within the last three
months.
Common side-effects include loss of appetite, constipation,
dry mouth and problems sleeping.
Rimonabant (Acomplia)
Acomplia is a new drug that blocks
CB1 receptors in the brain and fat tissues that control appetite and the desire
for sweet and fatty foods. This reduces appetite and cravings for these types
of foods.
A doctor can prescribe this drug if you are obese or have a
BMI higher than 27 with a risk factor for heart disease. The NHS guidelines say
it should only be given to people who’ve tried Xenical and Reductil and they
haven’t worked.
Common side-effects include nausea, nose and throat
infections, and psychological problems such as depression and anxiety. For this
reason, this medicine isn’t suitable for people who are vulnerable to mental
health problems.
What about weight reduction surgery?
You can be considered for weight-loss surgery if you are
morbidly obese, or if you have a BMI between 35 and 40 and have a risk factor
for an obesity-related disease.
This type of surgery is known as bariatric surgery.
Gastric banding
Gastric banding or 'lap banding' limits the capacity of the
stomach so you feel full after eating a small amount of food.
Keyhole surgery is used to tie an inflatable band around the
top part of the stomach, creating a small pouch at the top. This limits the
amount of food your stomach can hold.
Food then slowly passes from the pouch into the lower part of
your stomach and on into your digestive system.
The operation is reversible.
Gastric bypass
Gastric bypass is permanent surgery on the stomach to reduce
the length of the digestive tract and stop food being absorbed.
A small pouch is created at the top of the
stomach.
Part of the intestine is then grafted to the top of this pouch
so food bypasses the stomach and much of the intestine, meaning it can't be
digested.
Gastric balloon insertion
Gastric balloon insertion is a less permanent type of surgery.
It is not widely available on the NHS.
A balloon is placed on the end of a thin, flexible tube called
an endoscope. It is inserted into your stomach via your mouth.
Liquid or air is then pumped into the balloon so it partially
fills the stomach. This creates a feeling of fullness.
The balloon is usually removed after six months.
Complications of weight-loss surgery include the usual risks of
surgery and long-term digestive problems such as nausea, heartburn, vomiting
and diarrhoea.
After surgery your body absorbs less food, but it will also
absorb less vitamins and nutrients. This means you are at greater risk of
diseases caused by vitamin and mineral deficiency such as anaemia and
osteoporosis.
In the long term
While plenty of diets and slimming products claim to offer quick
fixes, obesity is not something that can be cured or brought under clinical
control within a few weeks or months.
Treatment such as diet and exercise may need to continue for
years.
Weight-loss plans from a GP or dietician are an effective way to
lose weight, but a greater challenge is to achieve a way of life that maintains
weight and reduces the chances of putting it back on.
This can only be achieved by permanently changing your eating
and exercise habits.
Further information
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BOSPA (British Obesity Surgery Patient Association) has
information on many types of weight-loss surgery: www.bospa.org
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National Obesity Forum:
www.nationalobesityforum.org.uk
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Based on a text by Professor Arne Astrup
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Last updated 30.06.2008
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