What are the health risks of being overweight or obese?

If you are overweight or obese, from day to day you may:

  • Feel tired and lacking in energy.
  • Experience breathing problems (for example, shortness of breath when moving around, or not being able to cope with sudden bursts of physical activity like running across the road).
  • Feel that you sweat a lot compared with other people.
  • Develop skin irritation.
  • Have difficulty sleeping.
  • Get complaints from your partner that you snore.
  • Experience back and joint pains which can affect your mobility.

You may also have an increased risk of developing:

  • Impaired glucose tolerance (pre-diabetes).
  • Type 2 diabetes.
  • High cholesterol or triglyceride levels.
  • High blood pressure.
  • Coronary heart disease.
  • Stroke.
  • Sleep apnoea (this is when your breathing patterns are disturbed while you are sleeping, due to excess weight around your chest, neck and airways).
  • Fertility problems.
  • Complications in pregnancy (including an increased risk of high blood pressure during pregnancy, diabetes during pregnancy, preterm labour, Caesarean section).
  • Stress incontinence (leaking urine when you are, for example, laughing, coughing, etc).
  • Gallstones.
  • Cancers (including colon, breast and endometrial (womb) cancer).
  • Gout.
  • Fatty liver.

Many people can also develop psychological problems because of being overweight or obese. For example: low self-esteem; poor self-image (not liking how you look); low confidence; feelings of isolation. These feelings may affect your relationships with family members and friends and, if they become severe, may lead to depression.

Being obese (having a BMI >30) can also affect your overall life expectancy: you are more likely to die at a younger age. An analysis in 2009 of almost one million people from around the world showed that if you have a BMI between 30 and 35, you are likely to die 2-4 years earlier than average. If your BMI is between 40 to 45, you are likely to die 8-10 years earlier than average.

Another analysis showed that if you are a woman who is obese at the age of 40, you are likely to die 7.1 years earlier than average. If you are a man who is obese at the age of 40, you are likely to die 5.8 years earlier than average. If you smoke as well, your life expectancy is reduced even further.

What is the cause of being overweight or obese?

In some respects, the cause sounds quite simple. Your weight depends on how much energy you take in (the calories in food and drink) and how much energy your body uses (burns) up:

  • If the amount of calories that you eat equals the amount of energy that your body uses up, then your weight remains stable.
  • If you eat more calories than you burn up, you put on weight. The excess energy is converted into fat and stored in your body.
  • If you eat fewer calories than you burn up, you lose weight. Your body has to tap into its fat stores to get the extra energy it needs.

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 your body needs to keep 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 may lead to weight gain, include the following.

How much you eat and drink

Most rich people live where tasty food can be found at almost any time of day or night. Many of the foods that people eat are those higher in calories (particularly fatty and sugary foods), so-called energy-dense foods. Although your body gives you a feeling of fullness after eating enough (satiety), you can easily ignore this feeling if you are enjoying tasty foods. Food portion sizes in general have increased. There has also been a tendency to eat out more over recent years. If you eat out, you are more likely to eat food that is more energy-dense than you would eat at home. The amount of processed foods and ready-made meals available has also increased in response to our busy lives. These are often foods that are more energy-dense as well. However, even healthy foods contain calories and can tip the energy balance if we eat too much of them. What you drink is also important. Alcohol and sugary drinks contain a lot of calories. Even fresh fruit juices that you may think are healthy can make up a significant part of your daily calorie intake if you drink too much of them. In short, many people are overweight or obese simply because they eat and drink more than their body needs.

Your physical activity levels

Where does physical activity fit in to your current lifestyle? Most people do not do enough physical activity. Fewer people these days have jobs which are energetic. The variety of labour-saving devices and gadgets in most homes, and the overuse of cars, means that most people end up using up much less energy compared with 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.


You are more likely to be obese if one of your parents is obese, or both of your parents are obese. This may partly be due to learning bad eating habits from your parents. But, some people actually inherit a tendency in their genes that makes them prone to overeat. So, 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 you eat, certain hormones and brain chemicals send messages to parts of your brain to say that you 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. However, if you do inherit a tendency to over-eat, 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. But you are likely to struggle more than most people where your weight is concerned. You may find it more difficult to stop yourself from gaining weight or to lose weight.

Medical problems

Less than 1 in 100 obese people has a ‘medical’ cause for their obesity. For example, conditions such as Cushing’s syndrome and an underactive thyroid are rare causes of weight gain. Women with polycystic ovary syndrome may also be overweight.
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 and, as a result, you may put on weight. People with low mood or depression may also have a tendency to eat more energy-dense ‘comfort’ foods and so gain weight.

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