Can drinking one less bottle of coke a day halve obesity?

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Hello, and welcome to the last in this series of More Or Less.

We are your ever-watchful guide to statistical wisdom and numerical tomfoolery.

And I'm Tim Harford.

This week, is the secret to halving obesity rates really just a matter of cutting back back on one fizzy drink a day?

How many new babies in the City of London have a foreign-born parent?

And since fewer than one baby a week is actually born in the City of London, how much should we care?

Electricity in the UK is more expensive than almost anywhere else.

Why?

And is it anything to do with windmills?

And we help out Start the Week with a claim about churches.

But first, many of you got in touch by emailing more or less at bbc.co.uk to ask about a claim made by Health Secretary Wes Streeting.

Discussing new standards to encourage food manufacturers and supermarkets to offer healthier food and thus cut the calories consumed by consumers, part of the government's 10-year health plan, he told Radio 4's Broadcasting House, For people who are obese, all it takes in terms of calorie reduction per day is the equivalent of a bottle of Coke, 216 calories, and we'd halve obesity rates.

Sounds pretty easy, right?

Well, not so fast.

This 216 calorie claim comes from research by Nestor, a charity that supports innovation in the UK.

And strictly speaking, Nestor's research covers not just obese people, as Wes Streeting said, but also people who are overweight but not obese.

If they all cut 216 calories on average, then rates of obesity would be halved.

At least, that's the idea.

And this idea came from modelling how much weight we'd all have to lose to get our wastes back to the size they were in the early 1990s, when obesity was about half what it is now.

That research involves a lot of assumptions, but the most important bit is the calculation that tells you how much weight you will lose if you eat and drink fewer calories each day.

For this, as they say in their paper, we defer to Hall et al.

2011 for full details of the model.

So we thought we'd defer to Hall as well, and that's Dr.

Kevin Hall, who recently retired in protest from the National Institutes of Health in the United States.

He figured out the weight loss model on which the Nesta calculation is based.

Yeah, if you want to know...

In theory, how much body weight would be expected to be lost as a result of that constant change in calories in the diet, then this is the tool that will allow an accurate assessment of that.

Kevin's model was an improvement on the simple calculations that we used before it because it took into account how the energy needs of the body change as people lose weight.

When you cut calories in the diet, the number of calories that the body uses changes in response.

And as you lose weight, the number of calories reduces.

So far, so good.

Now, the 216 calorie claim involves some simplifications.

It assumes the population is just maintaining their weight overall, not gaining weight, which would obviously offset the reduction.

But in general, says Kevin.

As far as I can tell, they've accurately implemented the model that we published in 2011.

But does that model work?

Well, it works well when you control what people eat.

So, in the way that these studies have been validated over years is that when we have really good measurements about what people eat, then the predicted weight losses match very closely on average with the simulated weight losses.

The challenge is what happens in the real world when you institute a intervention to try to change people's calorie intake.

The problem with these calculations isn't that they're wrong exactly, it's that they miss out a variable that turns out to have a huge effect, appetite.

When it comes to losing weight, your physiology is not your friend, as Kevin and colleagues demonstrated in a neat study in 2016.

They used a drug usually used for treating diabetes to secretly lower participants calorie intake.

They basically peed out the calories.

The researchers found that as these unwitting dieters lost weight, their appetite increased to counteract the weight loss.

As they lost weight, they gradually ate more and more calories.

And what we realized was that as people lost weight, for every kilogram of weight that they lost, they wanted to be eating about 95 calories per day above their baseline weight stable amount.

So what that means is that as people lose more and more weight, a constant intervention is fighting a greater and greater battle against the physiology that's increasing appetite.

And so as a result, what you get is instead of a constant cut in calories, you get a sort of exponential waning of that over time, even when the intensity of the intervention, be it surgery or drugs or a really intensive dietary intervention on lifestyle, that waning is to be expected because of the basic physiology of appetite control.

He found that to maintain a steady rate of weight loss with a fixed reduction of calories consumed each day, you have to put up with increasing levels of hunger as your pesky appetite strains to get you back to where you started.

If you're able to, for whatever reason, have a certain level of hunger that you're willing to live with over time, and that allows you initially to cut a certain number of calories from your diet, then yes, you'll begin to lose weight.

But for that same given level of hunger or the same amount of effort that you're putting into keeping that reduction in calories, in fact, your calorie intake will climb over time.

And eventually you'll rebalance at a level which gives you much less weight loss than if you had not accounted for that increase in calorie intake over time.

People turn out to be incredibly bad at figuring out how many calories they're eating and keeping track of the level of your own hunger over time is also nigh on impossible.

So people eat more calories as they lose weight until the effects level out, which means that the effect of any weight loss intervention is much smaller than you think it's going to be from the calorie maths.

I mean, much smaller.

My back-of-the-envelope calculations, based on what we've kind of updated since 2016 in the model versus what was in the 2011 model, is that you would only expect about 20%

of the predicted weight loss for a given intervention.

What you'd need to have is at the outset of the intervention, more like above a thousand calories per day cut, because that will eventually basically wane to something like the 216 calorie per day number after about a year.

So the problem is not that the 216 calories is the wrong number, it's that if you aim for cutting 216 calories from your daily intake, eventually you become so hungry that you're not cutting many calories at all.

The overall impact on your weight is the equivalent of cutting 40 calories a day, but sticking with it.

Kevin's research is about obesity interventions such as diets, drugs, and surgery.

Here he says it is clear you need a big cut in calories to seriously change weights.

But as to whether this also applies to the kind of government policy Labour have announced, which aims to change the products, prices and marketing in supermarkets, it is not yet clear.

That interaction between our food environment and our basic physiology is something that scientists are only beginning to work out.

So the number WesTreating used isn't exactly wrong, but it's certainly not a simple question of just avoiding a bottle of Coke.

When we spoke to Nestor about the figure, they were happy to accept that it is by no means certain that the policies would lead to the suggested weight loss.

But they said, if the effect of the policies is even a tenth of that hoped for, the cost-benefit analysis still makes sense.

Our thanks to Dr.

Kevin Hall.

Matt Goodwin, a political scientist, right-wing pundit and presenter for GB News, recently posted this on the platform formerly known as Twitter.

In the city of London, some 84% of babies now have at least one foreign-born parent.

In Leicester, it's 71%, in Manchester, it's 65%,

in Birmingham, it's 62%,

in Nottingham, it's 57%,

and in Bradford, it's just surpassed 50%.

Some big stats there, but hang on.

Isn't the City of London only 2.9 square kilometres, about the size of a few hundred football fields?

Since most of that space is occupied by skyscrapers, champagne bars and big piles of money, the actual liveable area only houses around 8,000 people.

Possibly not the best place to look at if you want a picture of the whole of London.

That being said, his stats are right.

They're from the Office for National Statistics, People, Population and Community Dataset from 2024.

If you look at their Excel spreadsheet, which we did, you find that, yes, 84% of people born in the City of London were indeed born to one or more foreign-born parents.

To put it another way, 45 babies were born in the City of London and 38 of them had one or more foreign-born parents.

Maybe it would be more useful to give figures for larger areas.

According to the ONS, 68% of the population of London have at least one foreign-born parent, and nearly 40% of the population of England and Wales have at least one foreign-born parent.

What you make of these numbers is a matter of opinion.

Clearly a lot of this is because we've had a lot more immigration over the last couple of decades.

But it is worth remembering that foreign-born doesn't necessarily mean foreign.

Our former Prime Minister Boris Johnson was foreign-born and also painfully English.

The ONS does not report the number of children for which he is responsible.

That is not all for exciting birth-based claims.

Another one that made the the headlines was that the number of births in England and Wales has risen for the first time since 2021.

Lovely.

The surprising demographic behind the first lift-in birth rate in years.

Several news outlets linked the increase in births to fathers over the age of 60.

But is this correct?

It is true that the number of live births has increased by 3,605 since last year.

It's also true that the number of of dads over the age of 60 involved in the production of these babies has gone up from 942 to 1076, that is an increase of 134.

But to put that into perspective, there were 594,677 live births last year.

So those extra 134 are really just a few tiny tadpoles amidst a mass of statistical swimmers.

While both numbers have risen, we cannot say that the majority of births have been jet propelled by geriatric fathers.

Apparently that's not the correct medical term, but it should be.

If you fancy being called a geriatric mother, congratulations, you can earn that title at the age of 35.

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Loyal listener Terry Cooper got in touch to ask us the kind of question that looks quite easy, but really isn't.

Do we have the highest industrial electricity prices in the world?

And if so, why?

Our energy price correspondent Richard Varden, also editor of this program, is on the case.

Hello, Richard.

Hello.

I have not seen you with your energy hat on since 2022.

Yes, the days after Russia's invasion of Ukraine, when gas prices rose hugely and all of a sudden domestic energy bills were at the top of the political agenda.

Since then, gas prices and bills have fallen, but bills are still high when compared to the years before the war.

But is it right that our industrial electricity prices are the highest in the world?

Yes, if you look at the figures the government publishes for electricity prices compared to peer countries, we are top of the charts and number one.

Go us!

Way!

Well hang on, that's actually a bad thing.

Makes British industry less competitive, reduces investment, costs jobs, harms economic growth.

Richard, why are we in the situation?

Well for the answer, I went to friend of the programme Hannah Ritchie, deputy editor of Our World in Data, the all-round experts in international comparisons.

Many other countries have deliberately given tax exemptions or levy exemptions for industrial producers in order to make sure that their industries are cost-competitive.

The UK, we have some exemptions, but they tend to be much, much lower and much, much weaker than in other countries.

So other countries have made a deliberate decision.

We want to prioritise industry, whereas the UK has not done that to the same extent.

But the problem isn't just for businesses.

We have the fourth highest domestic electricity prices.

Electricity prices are just high here.

Now I don't like to ask the obvious question, but I think in this case it's warranted.

Why?

Well a bit of background first.

In 2005 across the whole year we used 35% coal in electricity generation and 4% renewables.

Now we use no coal at all but 35% solar and wind.

This is a big change and we now emit only 20% of the carbon in electricity generation that we did in 2005.

But clearly making this change involves costs.

We've had to build a load of wind turbines and install loads of solar panels.

Also we need other energy sources to be able to keep the lights on when the wind doesn't blow and the sun doesn't shine.

So there are some big benefits but in the UK we've chosen to pay for it by sticking costs on industrial and household electricity bills rather than the government paying for it out of taxation.

Clear enough so far, I have a feeling though that things are going to get a bit more complicated.

Yes, I'm afraid I'm going to have to explain marginal cost pricing and to do this I've come up with a metaphor.

I love a good metaphor.

I'm not sure you're going to like this one.

Okay, let's imagine imagine I have a big garden and I need some of the more or less team to work in my garden this weekend.

I'm not sure how many I'll need, but I need some of you, maybe all.

I think at this point, Richard, I should make it clear that I am not going to come and do your gardening.

Okay, come on, Tim.

You're an economist.

You'll do anything for the right price.

£100 an hour.

That was easy.

So we're going to have to use a bit of clever economics to solve this problem.

I'm prepared to pay my gardeners, and all you have to do is tell me privately what price per hour you want.

For you, apparently, that's £100 an hour.

I presume you were talking about gardening.

If that's what you want to think then fine.

I've asked the rest of the team and their prices for gardening range from £40 an hour for Lizzie to a minimum wage of £10 for Nathan because he's only £18.

Now if I only need one of you that's easy.

I pay Nathan and the gardening cost will be £10 an hour.

But what if I need more of you?

If I want to hire Lizzie as well, I need to pay her and Nathan the same amount.

Those are the rules of the auction.

That's £40 each, so the gardening is now costing £80 an hour.

And if I want to hire you as well, I'm going to have to pay Lizzie and Nathan as much as I pay you.

Yeah, we could never have a system where I was paid much more than everyone else.

No, we couldn't have that.

So I'm going to have to pay everyone £100 an hour, even Nathan.

So it will cost me £300 for an hour's gardening.

Okay, I understand that.

That's the rules of the auction.

Let us now leave the garden metaphor.

Or is it an analogy?

Anyway, we'll leave the garden.

Let's get back to electricity.

Well, the electricity market works in the same way.

Different electricity generators make bids to supply electricity.

For an extra an hour of electricity, if the wind is blowing or the sun is shining, renewables are going to be cheap.

Nuclear is likely to be in the middle.

Gas is going to be the most expensive because, well, natural gas is expensive.

Now, if we have a lot of renewables, we might not have to use gas.

But whenever gas generation is needed, the price leaps up, not just for gas, but for nuclear and renewables too.

They're all getting the same price as gas.

And this is what usually happens.

Gas sets the price 98% of the time according to Emma Pinchbeck, chief executive of the Climate Change Committee, although some people have suggested to us that the figure could be lower.

And that gas price includes extra taxes to discourage industry from using fossil fuels which are equivalent to 7% of the household bill.

So it's all the fault of gas.

We just need to use less gas, presumably by using more nuclear and more renewables.

I'm sorry, but again, it's not that simple.

First of all, it's hard to use less gas.

We don't have a huge nuclear fleet like France, lots of hydropower like Norway or coal-fired power stations like Germany.

We are also on the edge of Europe so we don't have as many interconnects to buy power from other countries.

We also have a lot of wind turbines in places like the north of Scotland where there aren't a lot of people and our grid isn't good at getting that electricity to the south where the people live.

So sometimes we are using gas in the south at the same time as we are paying wind farms to turn off in Scotland.

That seems mad.

So who's paying for that?

We are.

If you look at a domestic electricity bill, the wholesale cost of the power generation, the bit where the price is likely set by gas, is less than 40% of the final bill.

It remains the biggest single item, but there are lots of other bits like paying wind farms to turn off.

I got Keith Bell, professor of electronic and electrical engineering at the University of Strathclyde, to talk me through some of the other costs that together make up the majority of a domestic bill.

So the next biggest bit would be for paying for the networks, so the transmission and distribution networks to get the power from where it's produced to where you are, paying for the infrastructure and paying for operation of those networks.

At the moment, that's about 22%.

And the next one after that is policy costs.

mainly paying for historic subsidies of the early kind of generation of renewables.

When we started building renewables, you know, wind and solar, it was actually quite expensive, but it was, you know, to align with emissions reduction policy, we needed to get going on that and start to build an industry.

And that's true from, you know, many countries around the world.

So to encourage anybody to build it, they need, effectively, needed a subsidy.

For instance, the renewables obligation and feed-in tariffs that were brought in when the sector needed a lot of help early in the push for renewables, they still put over 10% on our bills.

Which is a lot.

Yes, the good news as far as our bills are concerned is that the renewables obligation will be gradually phased out between 2027 and 2037.

It's been replaced with a different mechanism which guarantees renewable providers an economic price to cover their investment.

That currently costs a lot less, perhaps 4% on domestic electricity bills.

Lots of the costs for transmission, distribution and having extra capacity would exist however we were generating power.

But they probably cost more because we use a lot of renewables, which are intermittent and often quite remote from population centres.

Finally, we have some extra costs which have nothing to do with power generation, like a charge to pay for the warm home discount or to pay for smart meters and of course VAT.

So how are we going to get our electricity prices down?

Well I ask that question to Professor Robert Gross who is director of the UK Energy Research Centre.

In the long run, by which I mean beyond 2030,

we need to re-engineer the system so that we're not relying on gas-fired power stations.

We've got more storage.

We might need to build some bulk storage, for example, in the form of hydrogen.

We're going to need much more flexibility in the way that, for example, electric vehicle charging could be moved around by time of day.

Thinking about whether industrial consumers can be more flexible in the way that they use their electricity.

So, we're going to need a much more flexible system that can accommodate more renewables without relying upon gas as the balancing item.

And that's the situation that we're in at the moment.

And that's part of the reason that we've got high high prices.

Well, thank you, Richard.

Thanks also to Professors Robert Gross and Keith Bell, and to Hannah Ritchie of Our World in Data.

Also, I need to thank some other people who have taken the time to talk to me in a series of very long research calls.

Ed Heslett, energy analyst at the Centre for British Progress, Joe Bush of Modo Energy, and Nicholas Layton Hall of MCOE Consultants.

Okay, that's enough.

You finish your Oscar speech off the stage.

The other morning, I was peacefully munching my toast when my ESP started playing up extra-sensory perception of a statistical kind.

You had something like 37 million church buildings.

I haven't verified this with Tim Harford, but I'll take your word for it that there are 37 million church buildings globally.

I haven't verified this with Tim Harford.

Tim Harford, Tim

We hear everything start the week.

Everything.

Anyway, Christianity is the most followed religion in the world, with 2.5 billion people ticking boxes on censuses, identifying themselves as Christian.

But 37 million churches does seem like a big number.

Or maybe it isn't.

Lizzie McNeil, our spiritual statistician of the week, has been looking into this claim.

Hello, Lizzie.

Hi, Tim.

Now, this does seem to be another case of data working in mysterious ways.

The claim definitely isn't omnipresent.

I first found it on the website Quora, where a user replied to the question, how many churches are there?

With there are 37 million churches in the world, with 34,000 Christian denominations.

Now, the user said he knew this answer because he was building a Christian website and needed to create the numbers for the business plan.

What?

Yeah, I don't know either.

I did more digging and found the number again quoted in a United Nations Environment Programme report about how to make places of worship more eco-friendly.

I contacted the author of the report who said, Some resources indicate that there are around 37 million churches, 4 million mosques, 20,000 synagogues, and hundreds of millions of temples.

But, with no doubt, they are in the dozens of millions.

Therefore, we are not confirming nor negating.

Equivocation.

Love to see it.

Yeah, They pointed me towards an article on a site about world attractions.

The Post again discussed how many churches there are and quoted the 37 million figure, which they said came from data from the Centre for the Study of Global Christianity at Gordon Conwell Theological Seminary.

Okay, did you get in touch with them?

What did they say?

Well, that's the kicker.

They responded to me saying that they couldn't find any evidence for that statistic, but that it could possibly be from a now defunct data set, and that they had since archived that variable.

Ooh, that sounds like the statistical version of consciously uncoupling.

Yeah, right.

So, do we actually have a number?

Well, the Centre for the Study of Global Christianity do put a figure at 4.2 million congregations, which suggests that either 37 million churches is an overestimate, or a lot of them are empty.

But we could also do some back-of-the-envelope estimates.

Go for it.

So, there are about 2.5 billion people who identify as Christian in the world.

If there were indeed 37 million churches, then that would be one church for every 65 worshipers.

Plenty of spare pews, then.

Yes, particularly since many people who identify as Christians are not regular churchgoers.

Now, we do have some statistics from the US about numbers of churches, and they suggest there are 760 Christians per church in the US.

Admittedly, some US churches are on a truly biblical scale, but still, if you extrapolate the rates for America to fit the rest of the world, you get around 3 to 4 million churches.

If churches outside America are smaller than in the US, you'd get a bigger number, but probably nowhere near 37 million.

Thank you, Lizzie.

That is all we have time for this week, and indeed this series.

But we will be back in September, refreshed and ready to calculate.

So please keep your questions and your comments coming in to more or less at bbc.co.uk.

My other podcast, Cautionary Tales with Tim Harford, is also available weekly on BBC Sounds.

And if you are ever unsure when to trust statistics, head to bbc.co.uk, search for more or less, and follow the links to the Open University, where you will find an animated guide.

Until next time, goodbye.

More or less was presented by me, Tim Harford.

The producer was Tom Coles, with Nicholas Barrett and Lizzie McNeill.

The production coordinator was Brenda Brown.

The programme was recorded and mixed by James Beard.

Our editor is Richard Varden.

Additional gardening by Nathan Gower.

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