What causes obesity?

  • Obesity and excess weight is caused when extra calories are stored as body fat and build up over time.
  • The world around us makes a big difference to our weight. It makes being healthy more difficult. 
  • Eating more healthily and being active when you can is important. But we also need the government to help make it easier for all of us to do this.

Calories in our food and drink give us energy. We use this energy up when we are active. If we take in more calories than we burn off, the extra calories are stored as body fat.

Storing more body fat causes us to gain weight, and too much can lead to overweight and obesity.

But it’s not as simple as eating too much and moving too little. Obesity is a complex issue with many root causes, and one of the biggest influences is the world we live in.


The world around us affects how healthy we are

There are things we can do to be healthier. But while we might think we’re in complete control of what we eat, we’re probably all being influenced more than we realise. It could be at work, in a restaurant or in a supermarket.

When unhealthy options are the easiest, cheapest, or only thing available, weight gain becomes more likely.

The world around us makes it more difficult to be a healthy weight.

  • Confusing food labels, and more fat, sugar and salt in our food make it harder to find healthy options.
  • Unhealthy food adverts and 2 for 1 deals everywhere mean we can’t avoid seeing unhealthy food.
  • Checkout deals, bigger portions and fast food on the go all tempt us to eat more.



Why are more people obese now?

Over time food has become cheaper, larger, tastier and more calorific. At the same time food advertising and marketing has become more sophisticated. For example, adverts, price promotions on unhealthy foods and where products are placed in a store all have an impact on our behaviour.

Selling food and drink is a big business. Millions are spent every year on influencing us to eat more unhealthily.

This makes it harder and harder to be healthy and is one of the main reasons that more people are obese now.


How does food marketing and advertising affect children?

Studies have shown children who are exposed to more junk food marketing are at higher risk of being overweight or obese.

Junk food adverts appear up to 9 times every hour at children’s peak viewing times. Research has found that children who remember seeing junk food ads on TV eat more calories through snacking.

It isn’t the only factor, but junk food advertising aimed at children plays a part and NHS figures show childhood obesity levels in England have reached the highest on record.

We need to stop the flow of aggressive advertising and put children's health first.


What can reduce obesity?

There are some things we can do to help us form healthy habits. But we also need the government to help make it easier for everyone to be healthy.

The government launched a new obesity strategy in 2020. They want to halve childhood obesity by 2030. Their plan includes commitments on:

  • restrictions on junk food marketing on TV and online
  • restrictions on how and where unhealthy food and drink can be promoted in stores

Cancer Research UK has been campaigning for more protection for children and families from junk food advertising since 2016.

It's not a done deal and there's a long way to go, but we are seeing changes in the right direction.

Find out more about what changes you can make to be healthier.


Smith R, Kelly B, Yeatman H, Boyland E. Food Marketing Influences Children's Attitudes, Preferences and Consumption: A Systematic Critical Review. Nutrients. 2019;11.

Thomas, C., Hooper, L., Rosenberg, G., Thomas, F. & Vohra, J. Under pressure: new evidence on young people’s broadcast marketing exposure in the UK. 1–4 (2018).

Townshend, T. & Lake, A. Obesogenic environments: Current evidence of the built and food environments. Perspect. Public Health 137, 38–44 (2016). http://journals.sagepub.com/doi/pdf/10.1177/1757913916679860

Impact on Urban Health. Breaking down the challenge of inner-city childhood obesity. https://urbanhealth.org.uk/insights/reports/bite-size

Department of Health. Healthy Lives , Healthy People : A call to action on obesity in England. CoIlege Dep. Heal. 51 (2011). doi:https://www.gov.uk/government/uploads/system/uploads/attachment_data/fil...


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