What causes obesity?

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  • Obesity and excess weight are caused by there being more calories in what someone eats and drinks than they burn through physical activity
  • The world around us makes a big difference because it makes healthy choices more difficult
  • Making healthy choices for yourself and your family is important, but we also need the Government to help make it easier for us all

Why are more people obese now?

Obesity is a complex issue with many causes, but one of the biggest influences is the world we live in.

While we might think we’re in control of what we eat, we’re probably all being influenced more than we realise. Whether we’re at work, in a restaurant or in a supermarket, when unhealthy options are the easiest, cheapest or only things available, weight gain then becomes more likely.

Over time food has become cheaper, larger, tastier and more calorific and advertising and marketing more sophisticated. For example, adverts, price promotions on unhealthy foods and where products are placed in a store all have an impact. Selling food and drink is a big business and millions are spent every year on influencing us to eat more unhealthily.

This is creating what is known as an ‘obesogenic environment’ – where trying to be healthy gets harder and harder.

What could make a difference?

Although there are small things we can do to help us make healthy choices (and you can find some tips at the bottom of this page) we also need the government to help make it easier.

There’s a long way to go but we are seeing changes. Thanks to the sugar tax, brought in early this year, companies are already reducing the amount of sugar in some drinks.

The government has also released its updated childhood obesity plan which includes a bold aim to halve childhood obesity by 2030. Part of the plan is to tackle how junk food is marketed at children and families, something Cancer Research UK has been campaigning for since 2016.

But it’s not yet a done deal. So read about our campaign to get the Government to restrict junk food ads on TV before 9pm here.

How does food marketing 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. Our research has found that children who remember seeing one junk food ad on TV a day could eat an extra 18,000 calories in a year - or almost 350 calories a week.

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.

How can I be a savvy shopper?

  • Plan your meals and write a list

Spending a little bit of time each week to plan your meals and write a shopping list, can help you get more healthy foods in, dodge impulse shopping and avoid falling back on convenience foods.

  • Don’t go shopping on an empty stomach

Even if it’s just a piece of fruit on your way to the supermarket, it could help avoid extra snacks ending up in your shopping basket. 

  • Check the labels

Checking the nutrition information panel can help you work out where sugar, fat and salt might be hidden. You can even download a label reading app such as FoodSwitch or Change4Life Food Scanner. 

  • Pile up the fruit, veg, wholegrains and pulses

By eating more foods that are high in fibre (like wholegrain bread or oats) - you’ll feel fuller for longer on fewer calories. And the more your plate is filled up with these foods, the less room there is for the unhealthy ones.

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).

Butland, B. et al. Foresight. Tackling obesities: future choices. Project report. (Government Office for Science, 2007).

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

Guy’s and St Thomas ’ Charity. Breaking down the challenge of inner-city childhood obesity. https://www.gsttcharity.org.uk/sites/default/files/Bite_Size_Report.pdf

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...

Boyland, E. J., Harrold, J. A., Kirkham, T. C. & Halford, J. C. G. Persuasive techniques used in television advertisements to market foods to UK children. Appetite 58, 658–664 (2012).

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For most adults a BMI of

  • 25 to 29.9 means they are overweight
  • 30 to 39.9 means they are obese
  • 40 or above means they are  very obese