and with it long-term conditions like diabetes and heart disease

that can plague adult health.

But maps like these could help us turn the tide

by helping us understand how influences from our environment

shape what we buy and eat.

Junk food is in the spotlight in many places

where children and families spend their time.

The reality is that unhealthy food is sometimes much cheaper

and much more available, especially

in areas of low income.

It's not only schools, it's not on at home.

Children might hang around with their friends

around the schools, so the environment around schools

is extremely important.

Researchers at Guy's and St Thomas' Charity are gathering

social, demographic, and economic data

at the neighbourhood level and then mapping it against obesity

rates across two London boroughs.

The result is a clear picture of what's really behind childhood

obesity numbers.

Most people think that childhood obesity

is about poor parenting and a lack of individual willpower,

when rather this is a societal issue.

Kids from a lower income background

are about three times more likely to be obese than kids

from a wealthier background.

Indeed, when you plot childhood obesity on a map,

it tracks one to one with areas of lower average income.

Healthier food costs more than unhealthy food.

But that's not the only reason income

and obesity are so closely linked.

Those who earn less have less access

to transport so they're more reliant on the shops

nearest to home.

And because some shops stock more healthy food than others

the type of shop available on people's doorsteps

will determine what they can buy.

Even in neighbourhoods where household incomes are roughly

the same.

In Peckham Rye, 65 per cent of shops

were displaying fresh produce, whereas it was 23

per cent in Camberwell Green.

I guess that's just one example of how one area might have

an abundance of nutritious food versus unhealthy

and another might have the reverse.

Which again will be one factor driving a difference

in child obesity rates.

And if you compared them again to an area which

had higher average income you'd probably

see an even bigger change in the food options available.

Where fresh food just isn't an option for the poorest

families, local schemes can be supported

to make it more accessible and affordable.

Guys and St Thomas' Charity approached us

because we work with local children's centres

to identify families who could benefit from free vouchers

to go and buy more fruit and veg.

For one voucher you get two mango, like one pound.

We accept that as a currency.

So just bring one voucher.

We give you two mango.

And it's really good.

We eat more fruits and vegetables daily so

that's the best advantage of the voucher.

We're seeing around about a 65 per cent increase

in the amount of meals that people

cook from scratch using the raw ingredients that they

can buy here from the market.

So that means they're eating less unhealthy food,

they're spending more time cooking

and eating together as a family, and all of that

has got to help them and benefit them in the long term.

Providing easier access to fresh food will work for some

neighbourhoods but not all of them.

Another data set reveals where parents are working the most

hours over a given week.

Time pressure affects almost every household

but for some it can be the last hurdle that prevents parents

cooking healthy meals at home.

If you're time constrained and you have less time

to travel to that supermarket, is the beef more further away

from your home to outsource healthier foods.

You also don't have time to cook at home.

So you will rely on ready-made meals,

on things that you can easily buy at the end of the day

if you're working two shifts.

And again this is going to impact

more disproportionately the households on lower incomes.

Healthier takeaways could soon offer more nutritious

meals for homes where fast food has become a necessity rather

than a luxury.

But changing what kids eat at home can only help so much.

Children buy their own food before and after school.

And in many cases, this is where they're

most at risk from unhealthy influences on our high streets.

If you take the bus home from school, where the bus stop is

might be where you also socialise

with people which might be where you also have something to eat.

So whatever happens to be there providing

food in an attractive way really influences what you eat there.

Teenagers, particularly in the bit of London where we work,

don't have a great deal of spaces to hang out.

Fast food takeaways are a place where teenagers hang out.

So that's another area to focus on, as well.

So these are all the different parties,

the different partners, that we need to be involved.

Reining in unhealthy advertising and providing more safe spaces

for teenagers after school would mean redesigning the towns

and cities we live in.

It's a massive task that won't be possible without government

intervention.

But there's already evidence of how small design tweaks can

change shopper behaviour, particularly in the grocery

stores and supermarkets where families spend the majority

of their food budgets.

Chocolates, things that are bad for you,

are really the things that you see first

when you go into a corner shop.

So those are the things that pop up first into your mind.

So they are going to influence your decisions.

You do really struggle to find a healthy product.

Sometimes its shelved at the back

and it's not at your height, it's not really at the bottom

or at the top.

So you know, your access to not only

it's less salient visually, but also it's harder for you

to reach out for those things.

If they come to pick up nuts or the salt-free on the top,

it's sold down the bottom.

But it keeps improving sales, specifically

for the cereal bars.

So when we change the cereal bars here, the sales nearly 50

per cent up.

You got to keep trying to do it.

I lost it, still I make money so I'm happy to do that.

The results from these schemes could persuade big businesses

and policymakers to take action against childhood obesity

at a national level.

If that's by changing our urban environments

to make healthy food the easiest option,

data could be the tool to show us how.