Obesity, weight and cancer risk

Be a healthy weightOur research shows that being overweight or obese is a cause of at least 12 types of cancer, which is why we recommend that people maintain a healthy weight to reduce their risk of cancer.

On this page:

> Being a healthy weight
> What is a healthy weight?
> What’s the science behind obesity and cancer?
> How many adults in the UK are overweight or obese?
> How many children aged 2-15 in the UK overweight or obese?
> Tips to help you stay a healthy weight

Being a healthy weight

After not smoking, being a healthy weight is the most important way you can protect yourself against cancer.

There’s strong evidence that being overweight or obese is a cause of at least 12 different types of cancer, which include:

It’s not just cancer that’s affected by obesity. Being a healthy weight can also help to reduce your risk of heart disease and type 2 diabetes.

What is a healthy weight?

Your weight is a balancing act between the energy you put in (calories from foods and drinks) and the energy you use (for normal bodily functions and what you burn during physical activity).

The average adult man needs around 2,500 calories a day and an average woman needs about 2,000 calories. If you eat or drink more than your body needs, you will put on weight. The reverse is also true: if you regularly use more energy than you take in, you will lose weight.

  • You can check your body mass index (BMI) to find out whether you’re a healthy weight for your height.
  • Measuring your waist is a good way to check if you are a healthy shape. Having a healthy waist measurement is linked to a lower risk of cancer, heart disease and type 2 diabetes.

What’s the science behind obesity and cancer?

Our research shows that there are several reasons for the link between body weight and cancer.

For example, we know that fat cells release hormones such as oestrogen. Excess oestrogen can increase the risk of some cancers, like breast and womb cancer, and promote their growth.

Storing too much fat can cause insulin resistance (where insulin becomes less effective at controlling blood sugar levels), which encourages the body to produce growth hormones. High levels of these hormones can promote the growth of cancer cells.

Body fat also stimulates an inflammatory response. Inflammation can promote the growth of cancer by encouraging cancer cells to divide. This inflammatory response may underpin the wide variety of different cancers that have been linked to obesity.

How many adults in the UK are overweight or obese?

Overweight = BMI between 25 and 29.9, while Obese = BMI of 30 and over. In all countries, men are more likely than women to be overweight.

NationOverweight %Obese %Overweight and obese combined % *
England362864
Wales362561
Scotland352863
Northern Ireland382765

How many children aged 2–15 in the UK are overweight or obese?

Children who are overweight or obese are likely to continue to be so in adulthood, and we know that overweight and obesity in adulthood increases cancer risk.

NationOverweight %Obese %Overweight and obese combined % *
England121628
Wales151934
Scotland151429
Northern Ireland17825

Tips to help you stay a healthy weight

Following four simple steps can make all the difference. If you’re overweight, losing even a few pounds will make a positive difference to your health.

1. Reshape your plate

Feel fuller on fewer calories by swapping high-calorie processed foods such as biscuits, cakes, crisps and fast foods like pizza, chips and burgers, for fibre-rich wholegrains, vegetables, pulses and fruit.

> Read about high-calorie foods and cancer prevention

> Get inspired by our healthy recipes

2. Keep an eye on portion sizes

Too much of almost any food can cause you to gain weight. So only eat when you’re hungry and opt for smaller serving sizes to make it easier to control how much you’re eating.

3. Read food labels

Food labels include lots of useful information to help us make healthier choices. Use the front-of-pack traffic light label to see, at a glance, if a food is high, medium or low in fat, sugar and salt. You can also use food labels to compare calorie content and see how many servings are in a pack.

> Our guide makes sense of food labelling

4. Be more active

Cutting down on screen time (time spent doing sedentary activities like watching television or using a computer) and keeping active can help you to maintain a healthy weight.

> Why not sign up for a running event to help keep you motivated?

> Get inspired with tips on moving more


*Obesity statistics come from the Health Survey for England 2019, the National Survey for Wales 2019-20, the Scottish Health Survey 2020, and the Health Survey Northern Ireland 2019-20