What are the health risks of obesity?

obese man xray Obesity can increase the risk of heart disease and diabetes among others

The number of people with obesity in the UK has more than trebled in the last 25 years. Doctors now say that the condition is reaching 'epidemic' proportions. Why are they so concerned?

What is obesity?

A person is considered obese if they are very overweight with a high degree of body fat.

Some experts believe obesity is responsible for more ill health than smoking. Being significantly overweight is linked to a wide range of health problems, including:

The impact of obesity in the UK

  • A Government report recently claimed that obesity will cost the NHS £6.4bn per year by 2015
  • In England data from 2011 shows that 24.8% of adults (16 or over) and 16.3% of children (2 -15) are obese
  • In Scotland data from 2010 shows 27.4% of adults and 14% of children are obese
  • Obesity is most prevalent in the North East of England and in the West Midlands

The most common way to assess if a person is obese is to check their body mass index. BMI is calculated by dividing your weight in kilograms by your height in metres squared.

If your BMI is above 25 you are overweight. A BMI of 30-40 is considered obese, while above 40 is very obese. A BMI of less than 18.5 is underweight.

Another useful method is to take a waist measurement because fat in the centre of the body (apple-shaped obesity) is much more strongly linked to health risks than fat more widely distributed on the arms and legs. Women with a waist of 80cm or greater and men with a waist of 94cm or greater are more likely to develop obesity-related health problems.

A new way of calculating BMI has recently been proposed as the standard assessment is less accurate for extremes of height - the short and the tall. The new calculator hopes to correct this.

Why do people become obese?

On average a physically active man needs around 2,500 calories per day, while a woman needs 2,000. If we eat any more, the extra energy is stored for later use, mostly as fat.

This mechanism was life-saving during our hunter-gatherer days when food was often scarce. However, the boom in plentiful, cheap food, coupled with a general decrease in physical activity, means that those stores of fat are rarely called on. Instead they continue to grow.

Michael Mosley

Could science improve the nutrition of millions?

So why don't people just stop eating foods high in fat and sugar if they know they can cause physical problems? Scientists are still searching for the answers, but it appears that our brains have been wired to encourage the consumption of calorie-rich foods, even at the expense of good health. Quite simply, these foods bring us pleasure.

One recent study revealed that an area of the brain related to addiction and reward - the nucleus accumbens - lights up when a participant is shown calorie rich, fatty foods compared to healthy food.

Another area of the brain associated with pleasant tastes and reward, called the orbitofrontal cortex, is activated when we eat fatty foods.

Childhood obesity

Obesity experts say parents are struggling with a multitude of problems when it comes to their child's weight.

They range from a lack of education about food, limited cooking skills, limited money to buy healthy food, long working hours, easy access to snack food and pester power.

Why do parents let their children get fat?

At the same time, people are increasingly living more sedentary lifestyles and therefore burning fewer calories.

Studies have also shown that housewives in the 1950s were significantly slimmer than women today. This could be because their daily lives involved much more physical activity, including walking more and having fewer labour-saving devices.

Therefore, some scientists argue that the rise in obesity is a result of our bodies' inability to adapt to the changing environment.

According to the NHS, another reason obesity is on the rise is because unhealthy eating habits are often passed down through families, due to a lack of good food education.

Unless obesity is tackled, the government predicts that 60% of men, 50% of women and 25% of children in Britain will be obese by 2050.

Obesity expert Dr Tony Goldstone explains why fat is bad for your health, and how even small amounts of exercise can be good for you

For more information on symptoms and treatments, please visit NHS Choices

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