What causes obesity?

The world around us affects how healthy we are

While we might think we’re in control of what we eat, we’re all being influenced by the world around us more than we realise. It could be while we are on the go, when eating in a restaurant, or when doing a food shop.

Sometimes unhealthy options are the easiest, cheapest, or only things available. This can lead to weight gain over time.

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 offers encourage us to eat more unhealthy foods.

• Bigger portions and fast food on the go tempt us to eat more and in bigger amounts.

We know that keeping a healthy weight is more difficult for some groups than others. Some people may live in areas that make it more difficult to keep a healthy weight. Healthier food options may be harder to access. There may also be more fast food outlets nearby or fewer places to be active. Some things can also make healthy habits harder to maintain. For example, stress, the cost of activities, certain types of jobs, and long working hours. 

Our health inequalities article explains why it’s harder for some people to eat healthily, because of things outside their control.  

The world around us also affects how active we are. Increased use of cars or public transport and more jobs where we sit still, can mean that we are moving less.

Find out more about how being active helps to keep a healthy weight.

Why are more people overweight or obese now?

In the UK, almost 7 in 10 adults (aged 16+) are overweight or obese. The proportion of people who are overweight or obese in the UK has increased in recent decades.  

Over time, food has become available in bigger portions with more calories. There are also new ways in which people can access fast food. Such as through delivery apps and more food outlets on our high streets. Food advertising and marketing has also become more sophisticated. Food adverts, price promotions, and where products are in a store, all have an impact on our behaviour. Shifts in society over the years may also mean people spend more time sitting. For example, at work, during travel and in leisure time.   

These things can make it harder to be healthy. This is one of the main reasons that more people struggle to maintain a healthy weight.  

What can reduce overweight and obesity?

We need the government to help make it easier for everyone to be healthy. 

Cancer Research UK has been campaigning since 2016 for Government-led change.

Since then, government has:

• Restricted junk food marketing on TV and online.  

• Restricted how and where unhealthy food and drink can be promoted in stores. For example, in England and Wales, junk food is now banned from being sold at shop checkouts or through ‘buy-one-get-one-free’ type deals. Similar rules are coming into force in Scotland in October 2026. 

• Required large restaurants, cafes, and takeaways in England to show calories in foods.   

• Introduced a tax on sugary soft drinks. This encourages companies to reduce the sugar in their drinks. 

• Started a new Better Health campaign to support people in creating healthier habits. 

In 2025, the UK Government published their 10 Year Health Plan for England. This includes their ambitions for reducing overweight and obesity across the population. We’ll be working hard to make sure the government fulfils these commitments.  

There’s still a long way to go for changes across the UK, but we are seeing steps in the right direction. 

Find out more