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What causes obesity or weight gain?

The amount of energy in food or drink is measured in kilocalories (kcal), commonly called calories. You bring energy (calories) into your body by eating and you burn calories by being active. When you eat and drink more calories than you use up, your body stores the excess calories as body fat. If you regularly eat more calories than you use up, you will start to gain weight.

Keep also in mind that some medications or medical conditions can lead to weight gain.

Speak to your GP if you’re concerned about your weight.

Obesity infographic

How does obesity increase the risk of heart and circulatory diseases?

Being overweight can lead to fatty material building up in your arteries (the blood vessels that carry blood to your organs). If the arteries that carry blood to your heart get damaged and clogged, it can lead to a heart attack. If this happens in the arteries that carry blood to your brain it can lead to a stroke or vascular dementia.

Body fat and body shape

Everyone needs some body fat to stay healthy. But too much, particularly around the waist, puts your health at risk.

We have different types of fat in the body.

Many people tend to worry about the fat they can feel, the one that sits directly under their skin. This is called subcutaneous fat. But it’s visceral fat, the fat that surrounds our internal organs such as our heart and liver, that is the bigger health risk.

Graphic showing fat around the organs

Visceral fat affects how your hormones work and can:
  • raise your blood cholesterol
  • increase your blood pressure
  • increase your risk of developing Type 2 diabetes.
All of these risk factors are closely linked with heart and circulatory diseases.
Carrying weight around your middle can make it harder for your body to use a hormone called insulin, which controls your blood glucose (sugar) levels. This can lead to Type 2 diabetes. Having high levels of glucose in your bloodstream damages your arteries and increases your risk of heart and circulatory diseases.
People who are ‘apple’ shaped (carry excess weight around their middle) are at higher risk than those who are ‘pear’ shaped (carry weight around their hips, thighs and bottom) because the fat sits around their organs.

Apple and pear shaped bodies with visceral and subcutaneous fat

Apple-shaped body with visceral fat around the organs (left) and pear-shaped body with subcutaneous fat under the skin (right).

How do I know if I’m overweight or obese?

There are two measurements commonly used to assess whether you’re overweight – Body Mass Index (BMI) and waist circumference.

Measuring your BMI

The first step to calculating your BMI is to measure your height and weight. Your GP or practice nurse can do this for you if you can’t do this at home.
Your BMI score will place you into one of four categories: underweight, healthy, overweight or obese.
As BMI doesn’t take muscle mass into account, you may find yourself in the overweight or obese category if you’re muscular.
Your ethnicity can also affect your health risk. For example, adults of South Asian and African Caribbean origin may have a higher risk of health problems at BMI scores below 25.
This is why it’s important to use other measurements to assess your health risk, like waist measurement.

Waist measurement

You can measure your waist to see whether you’re carrying too much fat around your middle. A larger waist measurement is often a sign that you have too much visceral fat.
It’s important to note that your waist measurement will not be the same as the measurement you use when shopping for your jeans or trousers.
To measure your waist, you’ll need a tape measure. You should place it halfway between the bottom of your ribs and top of your hips, and hold the tape measure firmly just above your belly button to take the measurement.
The recommended waist measurements are:
  • below 37 inches (94cm) for men
  • below 31.5 inches (80cm) for women.
Adults of South Asian origin are at very high risk of health problems if their waist measurements are higher than the recommended measurements.

What can I do to lose weight or manage my weight?

To lose weight, you may need to change your eating habits and be more active. The best way to do this is to start with small changes – as they add up, you could see some big results. Here are some of the changes you can make to lose weight:

  • Visit our taking control of your weight hub for information and top tips.
  • Eat the right portion sizes
  • Eat a healthier diet
  • Read food labels and avoid things labelled in red
  • Be more active

Visit our healthy living page for more tips on small changes you can make.