17th January, 20215 min read

What are the health risks of being overweight or obese?

Medical reviewer:
Dr Ann Nainan
Dr Ann Nainan
Daniel Piggott
Daniel Piggott
Last reviewed: 30/12/2020
Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

Being overweight or obese means weighing more than is thought of as healthy, and happens when you build up too much body fat. It’s a common problem in many parts of the world, and unfortunately, it increases your chances of having certain health conditions.

But taking steps to keep to a healthy weight can help prevent these conditions, as well as improving your overall health. Read on to learn how to work out if you’re overweight or obese, what health conditions you might be more likely to get, and what you can do to reduce your risk.

How do you know if you’re overweight or obese?

Not sure if you’re overweight or obese? Body mass index (BMI) is the most commonly used way to check if your weight is healthy.

Your BMI is your weight in kilograms divided by your height in metres squared.

Your BMI score will tell you which of these 5 weight categories you’re in:

  • below 18.5 – underweight
  • between 18.5 and 24.9 – healthy weight
  • between 25 and 29.9 – overweight
  • 30 to 39.9 – obese
  • over 40 – extreme obesity

What health problems are more likely if you’re overweight or obese?

Being overweight or obese means you’re more likely to have high blood pressure (hypertension), which puts a strain on your heart and blood vessels. If it’s not treated, high blood pressure increases your risk of:

  • heart disease, such as coronary heart disease, which can lead to a heart attack
  • vascular disease, which can either affect the blood vessels or the blood supply to the brain and cause a stroke
  • kidney disease, when the kidneys stop working properly

A high BMI also increases your risk of:

Your sexual and reproductive health can be affected, too. Being overweight or obese increases your chances of being unable to have children (infertile), and you’re more likely to have complications during pregnancy, such as gestational diabetes.

Why does being overweight or obese make some health problems more likely?

The reasons for your weight affecting your health are complex and varied.

For example, if you have a high BMI you’re more likely to have high blood pressure. This puts a strain on your heart, blood vessels and blood (cardiovascular system), as well as your lungs and airways (respiratory system). This can then cause damage to those parts of your body – such as your heart, for example.

When one part of your body (such as your heart) works less well, other parts (such as blood vessels) have to work harder – which creates a ‘snowball effect’. Over time, this can lead to damage and changes to other body parts, and more health problems.

The fact that your body contains more fat and carries more weight when you’re overweight or obese also plays a part in increasing the risk of cancer, type 2 diabetes and high cholesterol, and problems with your joints.

Man measures his abdomen with a measuring tape

Is being obese a bigger risk than being overweight?

Having a high BMI increases your risk of high blood pressure, heart disease, stroke and type 2 diabetes. The risk may be even higher if you’re obese, but being overweight still increases the likelihood of these problems.

What can you do to reduce the risk?

Having a BMI in the ‘healthy weight’ range will reduce your risk of the health conditions above. If you’re overweight or obese, making changes to your lifestyle can help you lose weight and keep it off.

The two most effective ways to lose weight are:

  • eating a healthy diet – generally, to lose weight in a safe way, you should reduce your daily food intake by about 600 calories. The best way to do this is by eating a balanced diet
  • taking regular exercise – to maintain a healthy weight, everyone should aim for at least 150 minutes of moderate exercise (or 75 minutes of vigorous exercise) per week. However, to prevent obesity or avoid regaining weight after being obese, you may need to exercise for longer every day. Speak to your doctor before starting an exercise regime.

For more ideas, you can read these tips on how to lose weight safely.

If a healthy diet and regular exercise isn’t possible, or isn’t helping you lose weight, speak to your doctor. They may suggest medication to help you lose weight and reduce your risk of health problems.

Young overweight woman running

Key points

  • if you’re overweight or obese, it usually means you have a high body mass index (BMI)
  • being overweight or being obese increases your risk of several health conditions, including heart disease, stroke and type 2 diabetes
  • the biological reasons for this increased risk are varied and complex
  • a healthy diet and regular exercise can help you keep to a healthy weight and lower your risk
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