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Why body fat is a health risk

Lesley Dobson / 28 November 2016

We read all the time that being overweight is a major health risk – but how does being very overweight affect our bodies, and why it is so dangerous?

health choices
Too many high-fat foods, overeating, and not getting enough exercise are all choices that could have serious consequences for your health.

There’s no easy way to say this, but we are becoming more and more overweight, according to a report from the UN Food and Agriculture Organisation (2013).

One in four British adults is now obese, and the UK is now at the top of Western Europe’s obesity league, with Ireland and Spain coming second and third.

Being overweight or obese has serious health consequences that are directly related to carrying too much weight. The health risks that come with being overweight or obese can change our lives and even kill us. Understanding the effects that being overweight or obese has on our bodies can be a first step towards making change that reduce your weight and improve your health.

Brain tricks for weight loss

How heavy is too heavy?

When your doctor, or other health specialist is trying to find out whether you are a healthy weight for your height, they will probably do this by calculating your Body Mass Index (BMI). This will give a good idea as to whether you are a healthy weight for your height. If you know your height and weight, you can find out your own BMI on NHS UK’s website at

A reliable way of finding out if you have excess fat is to measure your waist circumference. This can be particularly useful for people who are;

  • overweight BMI of 25 to 29.9
  • obese BMI of 30 to 39.9
  • severely obese BMI of 40 or over

You can find the NHS Body Mass Index (BMI) calculator on this NHS Choices web page.

Being overweight, obesity and your heart

Knowing how being overweight or obese links to serious health risks is important in helping to understand why reducing your weight is so vital to your health. Here are some examples of the link between being overweight and obesity, and life-changing health problems.

Being overweight, obesity and high blood pressure

High blood pressure (over 120/80) can increase your risk of health problems. And the higher your blood pressure,  the greater the risk to your health. High blood pressure can cause heart attacks and heart failure. High blood pressure is also one of the chief causes of stroke, kidney disease, and it can also be a cause of dementia.

10 lifestyle changes to help lower your blood pressure

If you have high blood pressure it means that the force at which your blood travels through your arteries is greater than it should be. The healthy level for blood pressure is below 120/80. If your blood pressure is from 120/80 to 140/90 or above, see your doctor for advice on how to bring your blood pressure down.

Obesity causes high blood pressure because the body has more fat tissue. This means the body needs a greater supply of oxygen and nutrients, and so needs more blood vessels, and more blood to pump through them.  This puts more pressure on the heart and on the walls of the arteries, which results in high blood pressure.

10 blood pressure-lowering foods

Being overweight, obesity, cholesterol and coronary heart disease

Cholesterol can be bad for your health. The unhealthy type of cholesterol is known as LDL (short for low-density lipoproteins). When you have too much LDL in your blood stream it can result in fatty deposits attaching to the walls of your arteries. These are known as atheroma (or plaques), and they cause a condition called atherosclerosis.

(HDL, or high-density lipoprotein is better for our health as it carries cholesterol from the cells, back to your liver. Here it passes out of our bodies as waste.)

What you need to know about cholesterol

Atherosclerosis causes narrowing and hardening of your arteries, and this can reduce the amount of space your blood has to flow through. If this happens,  it means that your heart, brain and other organs won’t receive enough vital oxygen-carrying blood. The pain this causes is known as angina.

In the worst cases, when your arteries are completely blocked, this will probably cause severe health problems, including strokes and heart attacks. These conditions can cause serious, life-changing health problems, and can kill you.

Being overweight or obese puts you at risk of developing atherosclerosis. Other risk factors include having an unhealthy diet that contains too many high-fat foods, over eating, and not getting enough – or any – exercise. All these factors also increase your risk of being overweight or obese.  

10 superfoods that help lower bad cholesterol

Being overweight, obesity and type 2 diabetes

Obesity is one of the main causes of type 2 diabetes. Being overweight or obese can dramatically increase your risk of developing type 2 diabetes. This is because being obese can mean that your body can become resistant to the hormone insulin. This is important, because insulin regulates your blood sugar. When your body develops insulin resistance, your blood sugar rises.

Obesity is clearly linked to your risk of developing type 2 diabetes, so being even moderately obese can increase your likelihood of becoming diabetic.

What you need to know about type 2 diabetes

Overweight, obesity and cancer

Being overweight or obese can really increase your risk of developing cancer. In fact, more than one in 20 cancers diagnosed in the UK may be linked to excess weight.

The extra fat that overweight or obese people have in their bodies, doesn’t just increase your weight, it is actively harmful. This fat creates hormones (including oestrogen, testosterone and insulin) and proteins (also known as growth hormones), that change how our bodies’ cells behave. These changes can increase our risk of developing cancer and other diseases.

These hormones and proteins travel around our bodies in our blood stream, so putting us at greater risk of developing different types of cancer in different locations.

Belly fat – found in people who have large tummies (known as being ‘apple shaped’), has been linked to a number of cancers, including bowel, kidney, oesophageal, pancreatic and breast cancer.

Eight ways to reduce belly fat

According to research carried out in this field, these are some of the cancers that are found more commonly in people who are overweight or obese;

  • breast cancer (in women who have been through the menopause)
  • bowel cancer
  • womb cancer
  • oesophageal (food pipe) cancer
  • gastric cardia cancer (a form of stomach cancer)
  • pancreatic cancer
  • kidney cancer
  • liver cancer
  • also probably gallbladder, ovarian and aggressive prostate cancers

Visit our cancer section for more information about cancer

The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.