Energy balance: explaining its links to cancer prevention

07 November 2018 | Science and research

We’ve published, today, the full version of our report into Diet, nutrition and physical activity: Energy balance and body fatness – the determinants of weight gain, overweight and obesity. Susannah Brown, one of our senior scientists, explains its key findings.

What is ‘energy balance’, and what is this report about?

Being in energy balance means matching the amount of calories you put into your body, through what you eat and drink, to the amount of calories your body uses up – through things like your normal bodily functions but also physical activity and exercise. If this is matched, long term, this is weight maintenance and your body weight stays the same.

Our report looks at the diet and activity factors that might influence energy balance. 

How is obesity related to cancer?

Our recent global cancer report showed that greater body fatness, including weight gain, increases the risk of 12 types of cancer. So it’s important we understand more about what factors can influence weight gain, overweight and obesity.

What does this new report say about screen time and obesity, and how is this linked to cancer?

We found strong evidence that spending more time in front of the television or on a computer (at work or at home) increases the risk of weight gain, overweight and obesity, which increases the risk of 12 cancers. This finding was particularly strong in children.

Obviously, just looking at a screen won’t lead to weight gain, but being inactive (sedentary) over long periods of time can shift your energy balance. Being sedentary can also interfere with your appetite, making it harder to recognise when you are full. 

This can be compounded by adverts for ‘junk’ food and drink that you may see during screen time, which are often targeted directly at kids. It’s also quite common to snack while watching screens – being distracted can lead to unconsciously eating more.

So is screen time the most important factor for obesity risk?

Our expert panel looked at research from around the world, reviewing multiple factors to do with diet and activity. They are confident that the links identified are to do with patterns of factors, rather than one single factor alone.

For example, spending more sedentary time in front of a screen, in combination with frequently eating ‘fast foods’, drinking sugary drinks and having a diet high in fat, sugars and meat, is more likely to lead to weight gain, overweight and obesity than any factor on its own.

However, diet and activity aren’t the only things that can influence energy balance, and ultimately body weight. For example, both genetics and wider environmental factors have roles to play.

Is it just about personal choice and responsibility?

People can take positive steps to help reduce their cancer risk, including maintaining a healthy weight. We have an online Cancer Health Check to support people in making changes that feel right to them.

But obesity is a complex issue influenced by many factors beyond individual control, such as the availability of different types of foods and how easy your neighbourhood makes it to be physically active. Changing these upstream factors through public health policy is critical to address the multiple drivers of weight gain, overweight and obesity across different communities and that’s why WCRF continues to call on governments to prioritise cancer prevention through the development and implementation of effective policies to address the rising burden of cancer in the UK and worldwide. 

Susannah Brown | 07 November 2018

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