My twin brother Xand is a perfect genetic copy of me. So I know, because I’ve been tested, that he and I share a gene that predisposes us to putting on weight.
This came as no surprise to me. I love food, and I’m constantly thinking about my next meal.
If you’re as obsessed with food as I am, then — regardless of what you weigh — you probably have these genes, too.
In my own case, I’m just a bit overweight. So you’d expect my genetically identical twin to weigh roughly the same, give or take a few pounds.
A few years ago, though, Xand was nearly 20kg (3 st)heavier than me. This is a huge amount, in fact the biggest weight difference of any pair of UK twins who’ve been studied by scientists.
So how on earth did my brother manage to become clinically obese?
Weighty issue: Dr Chris van Tulleken (left) with his twin brother, Xand
His weight problem began when he won a scholarship to an American university to do a masters degree. Quite suddenly, he was living in the middle of a food swamp.
You may have heard of food deserts —places where shops sell only ultra-processed food (UPF). In the UK, more than three million people don’t have a shop selling raw ingredients within 15 minutes of their homes by public transport. This means it’s difficult to source real food — let alone cook it.
Food swamps are similar to food deserts. Fresh food may be available, but it’s submerged in a swamp of fast-food outlets selling UPF.
And there are plenty of these swamps in the UK. Take Leicester, where a group of teenagers kindly showed me round the place where they all regularly hang out.
At the Clock Tower, a central landmark, they pointed out the shops in the immediate vicinity: McDonald’s, Five Guys, Burger King, KFC, Greggs, Tim Hortons, Taco Bell, another Greggs, Pizza Hut, a chicken shop, Costa, Awesome Chips.
All these outlets sell UPF — edible substances reconstructed from whole food that’s been reduced to its basic molecular constituents. These are then modified and re-assembled into food-like shapes and textures and then heavily salted, sweetened, coloured and flavoured.
Many of the chemicals used have never before been eaten by humans. And evidence is growing that many of them raise our risk of everything from cancer and heart disease to dementia, colitis and diabetes.
So how can you avoid UPF if you’re one of those teenagers in the Leicester swamp? The answer is that it’s all but impossible.
‘A few years ago, though, Xand was nearly 20kg (3 st)heavier than me. This is a huge amount, in fact the biggest weight difference of any pair of UK twins who’ve been studied by scientists’
It’s not just the density of fast-food UPF outlets that matter, it’s also the marketing. The teenagers showed me their bus tickets, which are also vouchers for McDonald’s. They also let me look at their social-media feeds, which are crammed with ads for UPF brands.
So are the online games they play. Even the songs they listen to on Spotify are interspersed with ads, largely for fast-food chains. The UPF industry, I realised, has an iron grip on their lives, to the point where McDonald’s has become their de facto community hub.
As one put it: ‘It’s where we hang out, because all the youth clubs have shut down.’
Like the kids in Leicester, Christina Adane — a young food activist from London who was behind the UK petition for free school meals — is aware of how much influence the food industry has over her and her friends.
‘It is scary how successful junk-food companies have been in infiltrating youth culture. Celebrities go on chicken-shop dates to promote new albums, energy drinks are advertised at every event celebrating up-and-coming young artists,’ she told me. ‘Not enough of us realise that these fast-food companies are not our friends. We’re living in a world where one in three children by the age of 11 is at risk of diet-related disease. One in three!’
Needless to say, my brother Xand had no idea that what he was eating might be harmful.
Living in the U.S., he’d found himself surrounded by far more UPF than he’d ever encountered in the UK. Soon, it made up the majority of his diet.
He was also stressed and far from home. And stress has a dramatic impact on the hormones that regulate appetite, increasing the drive to eat more.
What is it about UPF that makes it seem irresistible? As Xand discovered, it’s available everywhere, cheaper than whole foods, quicker to prepare and so soft that it slips down a treat. But that’s not all; added flavouring also draws us in. I talked about this to Barry Smith, an expert ultra-processor who used to advise food companies.
The UPF industry, he explained, exploits the fact smell influences taste. One of Barry’s favourite sensory tricks involves ice-cream.
‘If you go into the freezer for an ice-cream bar, as you rip open the packet, it won’t smell of anything, because it’s too cold,’ he said. ‘So, lots of companies add a scent in the wrapper’s ribbing.’
This not only starts a craving, but it makes us experience the chocolate more intensely.
This trick is probably OK if it leads to real chocolate. Other tricks, however, are actively misleading — such as delicious smells in products so over-processed that they contain no nutrition at all. You can see why manufacturers go down this route. If you get a whiff of barbecued beef, say, you’re more likely to eat an industrially processed substance that has little relation to the real thing.
Mark Schatzker, who belongs to a nutrition research group at Yale, believes the use of flavourings is one of the main problems with UPF. For humans, he says, the way a food tastes and smells is a signal it contains particular nutrients. When we eat an ultra-processed version of real food, however, we simply aren’t getting what its flavouring promises to deliver.
‘It’s not just the density of fast-food UPF outlets that matter, it’s also the marketing’
Bear in mind that there are more than 26,000 chemicals in some whole foods, many of which may be responsible for giving us protection against cancers, heart disease, dementia and early death. But most of these chemicals are stripped out by ultra-processing. The result is lots of calories, but little other nutrition.
This means that if most of our diet is UPF, as it is for most in the UK, we become increasingly deficient in micro-nutrients.
The outcome, says Schatzker, is that our bodies search for nutrition that isn’t there, and we end up eating even more UPF.
Throughout UPF, there’s a mismatch between what we taste and the promised nutrition that never arrives. For instance, the gums and pastes found in so much processed food create a sensation of fat in the mouth.
What is it doing to us? And what happens to our bodies when these fake fats are combined with artificial sweeteners — as in low-fat mayonnaise or zero-fat yoghurt? Unfortunately, no one knows.
Then there are all the other additives — from humectants and emulsifiers to preservatives and bleaching agents.
How can we be confident any one them is 100 per cent safe? Well, here’s just some of what we know from scientific studies:
- When tested on children, six artificial colours were found to make them hyperactive.
- The preservatives and emulsifiers in UPF can disrupt the microbiome.
- Xanthan gum — common in UPF — encourages the growth of an entirely new bacterial species in our gut, whose effects have yet to be determined.
- In experiments with mice, maltodextrins — synthetic chains of sugar molecules commonly found in UPF — encouraged dangerous bacteria like salmonella and E.coli. In humans, maltodextrins may also be linked to the rise in disorders such as Crohn’s disease and type 2 diabetes.
- Many commonly used emulsifiers — including glycerol stearate, sorbitan monostearate, and carrageenans — have been shown to alter overall levels of beneficial bacteria in our microbiota.
But even if we decide to avoid all these chemicals, there are thousands of additives in UPF that haven’t yet been studied. So we have no idea which of them may be doing us long-term harm. Want to know how easy it is to get a new additive approved?
Let’s say you live in the U.S. and have just invented a new one for use in an ultra-processed corn oil.
You can either apply for approval from the FDA (Food and Drug Administration), which means submitting a lot of data for a process that could take years.
Or you can pay scientists-for-hire to certify — without any long-term experiments — that your additive is considered ‘generally recognized as safe’, or GRAS. After that, you apply to the FDA for a GRAS certificate, enclosing a bit of data, and bingo — with any luck, you’re in business
This is what one corn-oil company did. Among the paperwork it sent was a diagram of the molecular structure of corn oil. In fact, corn oil doesn’t have a molecular structure.
Also, when I looked at it, the diagram looked awfully familiar. In a pharmacology textbook, I discovered the company had sent in the molecular formula of an HIV drug, presumably by mistake.
The FDA also identified deficiencies in this company’s GRAS application. But not to worry — the oil producers then decided to take the third option. They just asked the FDA to stop evaluating their new additive. The oil with the new additive could then, perfectly legally, be put on the market.
This was because there’s such a backlog in GRAS applications that, since 1997, U.S. companies have been allowed to decide themselves whether an additive is safe.
So in the case of the oil company, their hired scientists — the ones who confused the molecular structure of corn oil with an HIV drug — gave it the green light. What this means is that the corn oil in your larder, or listed as an ingredient in your lunch, may well be full of unlicensed additives and antibiotics. Yet all you’ll see on the label is ‘corn oil’.
An extreme example? I doubt it. Since 2000, there have been only ten applications to the FDA for full approval for a new substance.
Over the same period, there’s been 766 new food chemicals added to the food supply. Which means that the other 756 have been ‘self-determined’ by the companies that make them.
‘I suggested to Xand that he also try my UPF diet, and he agreed. On day three, he stopped eating UPF and within three months, he’d shed his surplus 20kg’
The ten applications for full FDA approval have been combed through by scientists. Only one, they discovered, had considered the cumulative effects of additives in a meaningful way.
Fewer than a quarter undertook the recommended one-month feeding study in animals. And fewer than 7 per cent tested for possible harms to human reproduction or development.
What if health problems emerge a few years down the line? Unfortunately, you may never be able to show they’re due to a particular additive because they’re not all listed on the labels.
In short, there’s no functional regulation of food additives in the U.S. to ensure food is safe. The process is essentially voluntary.
The situation in Europe is somewhat better, as the EU maintains a database of new chemicals and periodically reviews additives. Even so, the words ‘obesity’ and ‘microbiome’ are pretty much absent from European Food Standards Agency reports.
The problem is that it’s really hard to test for longer-term effects — so those tests don’t get done.
There’s an ethical question here as well. A single two-generation test for reproductive safety, for example, might need to use more than 1,000 animals.
I doubt many of us think food colouring is a good reason to kill so many creatures. Also, we’re not rats or rabbits: we metabolise substances very differently.
So why aren’t we doing tests on humans? Either ethics committees are declining these proposals, or they’re not being funded.
Or perhaps volunteers to drink a 1 per cent polysorbate solution for a year are in short supply. (Who’d want to drink an emulsifier already known to cause low-grade inflammation and weight gain at just a tenth of one per cent?)
So a tiny number of academics and activists are doing what should be the government’s job.
But back to my brother Xand, and his 20kg weight gain. I grew increasingly concerned about his health — particularly when he had Covid much more severely than I did because of his weight.
Meanwhile, I’d decided to do an experiment (see Saturday and Sunday’s extracts), which involved eating 80 per cent UPF for a month and measuring the harm it did to my body. The result was shocking, and made me vow to cut UPF out of my diet entirely.
I suggested to Xand that he also try my UPF diet, and he agreed.
On day three, he stopped eating UPF and within three months, he’d shed his surplus 20kg.
I’d recommend this method to anyone. If you want to stop eating industrially produced substances, just pig out on an 80 per cent UPF diet for a few days and see how you feel.
Like Xand and me, you may well conclude it’s best to avoid the stuff altogether.
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