Joe Wicks and I have created Britain's most dangerous 'health' snack. This is what's in it, why we've made it and everything it tells us about Britain's UPF scandal: PROF CHRIS VAN TULLEKEN

Joe Wicks and I are launching a new, ultra-processed protein bar today.

As you might expect, we're marketing it as being incredibly healthy: there's a picture of Joe on the pack exuding wholesome vitality, alongside boldly presented claims of '19g protein', '27 vitamins and minerals', 'high fibre' and, most importantly, '200 health and nutrient benefits'.

We've carefully engineered it so it's tasty – moreish, even – with a chocolately orange flavour, one of Joe's own favourites.

But this bar is not actually healthy. In fact, our 'healthy' protein bar may also be Britain's most dangerous snack.

We're not hiding this fact – flip the packaging over and you'll see that not only is our bar high in saturated fat and sugar, it's packed with 96 ingredients (see box), some of which, as the label tells you, are linked to dementia, cancer, early death – and diarrhoea.

Yes, diarrhoea: Joe's bar could literally give you the runs.

And Joe and I want you to buy it.

Have we lost the plot? You might think so. After all, I've made documentaries and podcasts, written a book and multiple articles (in the Daily Mail!) about how harmful ultra-processed food (UPF) is.

And Joe is famous for his efforts to improve the nation's diet as well as fitness.

But despite our efforts – and those of others – our health statistics just get worse. A big part of the problem is that unhealthy food comes without warnings.

In fact, if a food has a health claim on its packaging, it's pretty much a rule of thumb that it won't actually be good for you.

Joe and I are furious about the fact that a product like our bar can be marketed as healthy.

And, as revealed in a new documentary for Channel 4, Joe Wicks: Licensed To Kill (broadcast next Monday), he and I deliberately made our bar as unhealthy as we could, using all perfectly legal ingredients, to ask this simple question: why don't foods that we know are harmful to health carry warning labels?

As you'll see in the programme, in some ways it was an enjoyable process, including when Joe and I were let loose in an industrial kitchen, in a protein-bar version of Breaking Bad. Our initial effort was brick-like (though Joe uses a ruder epithet you'll hear).

We also teamed up with veteran chef and food development expert Amir Mousavi, who revealed tricks of the UPF trade.

We added maltitol, a type of sugar alcohol that provides bulk and moisture, and a dense, almost fudge-like bite. Sugar alcohols aren't sugar so companies can label products as 'no added sugar or 'low sugar'.

But it can cause diarrhoea – something you would experience after just a couple of our bars. We added as much maltitol as we could.

There's also aspartame, a sweetener that has been associated with a higher risk of stroke – and a carcinogen, according to the WorldHealth Organisation. Again, we added lots.

To make the bar chewable, rather than needing a chisel to eat (as with our initial effort), Amir suggested adding glycerol syrup, a sweetener and humectant found in slushie drinks – which at high levels can cause intoxication and loss of consciousness in children.

There's also maltodextrin, a sweet thickener that lab studies show increases intestinal inflammation. Essentially, we added bowl after bowl after bowl of white powders, as Joe put it – in this bar there's basically only one ingredient that any of us might have in our kitchens: cacao (for the chocolate taste).

We didn't need any approval from a regulatory authority for our bar, as we stuck to the permitted levels of our 96 (approved) ingredients.

We had a lot of fun making it, as well as a few digestive troubles after the taste trials, but there is a really serious point to this.

At the moment, the foods with the biggest health 'halo' are protein bars – now a multi-billion-pound industry, with social media and sport health influencers relentlessly pushing them.

Essentially, they're pushing junk food. I don't blame the influencers: they're not nutrition experts and protein bars are a great example of foods that promote themselves as health products, while in reality they're ultra-processed, with high levels of salt, sugar, fat, calories and additives known to cause harm.

UPFs, to remind you, are industrially produced, packaged foods made using processes that you could not replicate in your own kitchen, with ingredients you wouldn't find in your home larder.

I think it's perfectly legitimate to ask if these products are even food at all because their purpose is not nourishment but profit – they're engineered so that you eat too much, and they're the basis of our diet in the UK.

After the US, the UK eats more ultra-processed food than anywhere on earth. The average adult's diet is around 60 per cent UPF – many children are eating much more.

And this stuff is really bad for our health. Almost all UPF has too much energy (i.e., calories) and/or salt, and/or sugar, and/or saturated fat; they also generally contain additives that are increasingly being linked to harm.

And even when the additives themselves aren't that harmful, such as flavourings, they're still making us eat the harmful salt, sugar and calories.

Not all UPF products are equally harmful – but when it comes to a diet high in UPFs the jury has returned, with clear evidence showing it can cause weight gain, obesity, inflammatory bowel disease, inflammation, some cancers, fatty liver, kidney disease, anxiety, depression, dementia, type 2 diabetes and early death.

That's right, a diet high in UPFs has been linked to early death from all causes – as many as 14 per cent of all premature deaths in England, according to a recent review in the American Journal of Preventive Medicine.

Indeed, on the back of our bar packaging there's a grim picture of Joe looking like the living dead.

Making and marketing this frankly awful bar is a brave stunt for someone like Joe, who has prided himself on trying to improve the nation's diet and health.

As you will see in the TV programme, he struggled with the idea of putting his name on this product – aptly named Killer – and the ethics (as well as legality) of making something we regard as dangerous.

I've definitely been more gung-ho about the stunt, as one of a number of experts who have campaigned on UPFs for years but who have had little obvious impact in the UK.

The combination of Joe, a national health and fitness treasure, and his genius idea of a making a protein bar that would be an embarrassment to regulators and politicians could be what finally shifts the dial.

While making a protein bar with ingredients we know can be harmful is clearly provocative, it's important to expose how light-touch the regulation around our food industry is – for the Killer bar is perfectly legal, if an extreme version of products that are already widely available. And the food industry wants us to consume ever more of this kind of thing.

As Joe reveals, when he was growing up his family had very little money and his diet was dominated by UPFs.

Even now he loves the taste of these foods. 'I don't just eat junk food, I love it,' he says.

And at the end of a tough day, he doesn't make himself a kale and quinoa salad, he'll go for a quick hit from Monster Munch and a can of Coke. I've experienced this, too: before I really understood UPFs I would happily eat Coco Pops for breakfast, a meal deal for lunch and KFC for dinner. They're cheap, convenient – and irresistible.

For the food industry has gone to enormous lengths to ensure we buy and eat more, and then still more of their cheaply produced, highly-processed products.

They've employed some of the best scientific brains, using the latest brain-scanning technology, to work out how to hijack our unconscious desires.

They've also gone to efforts to prove this food is safe – first, by funding their own studies (industry funding is known to create bias, sometimes deliberate, but probably most of the time unconscious).

Then, drawing a leaf out of the tobacco industry's playbook, they don't attack the negative findings of studies into their products; they attack the methods used to obtain those findings, creating a cloud of apparent confusion.

This is because it's impossible to conduct a watertight study on the effect of ultra-processed foods (or any foods for that matter) on people. This would require taking thousands of infants, and locking them up inside labs for decades to see what happens when they're split into different groups and given specific UPFs.

Instead, scientists have to rely on different methods to investigate 'causality' – very large population studies that examine food-consumption habits and participants' health over several decades.

These show consistent associations between diets high in UPF and obesity, heart disease, type 2 diabetes and cancer.

The food industry-backed scientists argue these associations are not strong enough to be actual proof.

But there are now more than 100 of the types of studies that linked smoking with cancer showing UPF is linked to health harms, as well as lab studies and clinical trials, so their argument becomes unsustainable.

Against this background, and all kinds of lobbying, successive UK governments have failed to take action to tackle the harms caused by UPFs. And, as Joe says, people 'aren't aware of the long-term effects these foods can have on us'.

That's where the Killer bar comes in. Its very existence deserves public outcry. Both sides of the political aisle and consumers can be reassured this is not about banning anything.

We just think companies should be required to put clear warning labels on food that exceeds the Government's existing guideline amounts for fat or sugar, for instance (as found in the NHS Eatwell guide).

What's wrong with the current traffic-light labelling system (where red indicates that the food is high in a nutrient, such as fat, that you should eat less of), you might ask. These labels aren't only voluntary, they create absurd situations in the real world.

Take the example of a 250ml can of Coca-Cola Original: out of four lights it has three 'greens' – for fat, saturated fat and salt. Yet it also has 27g (around seven teaspoons) of sugar in just one can.

And guess what? Despite exceeding UK government levels for saturated fat and sugar, the Killer bar only gets amber lights. It's also high in calories (129 in a small 35g bar) but there's no traffic light for calories, even though we know energy is a key driver of weight gain.

There are further regulations coming into action next year around the marketing of 'less healthy' HFSS (high in fat, sugar or salt) foods, restricting how they can be advertised or placed in shops.

Yet it's a point system that can be gamed by adding a 'good' thing, such as protein, to a HFSS food, lowering the overall score (ever wondered why there are so many 'added protein' products, from yoghurt to pasta and muffins?). The Killer bar wouldn't register on the HFSS radar.

The current UK system of HFSS and traffic lights won't inform you about a food's healthiness or otherwise. What we need is a mandatory food warning label system like the one introduced in 2016 in Chile, for foods high in salt, saturated fat, sugar or calories.

The Octagon Warning Labels (OWLs) are stark and clear on the front of the pack. They look like a black stop sign. If a product has an OWL, it cannot be marketed to children.

In Chile, OWLs have significantly reduced consumption of high fat and sugar foods. The scheme is now being rolled out across most of South America. Under Chile's model, Killer would score three OWLs (see box).

Surveys show there is enormous public support for better food regulations and labelling. We already have guideline amounts for macronutrients such as sugar – what we need is stronger labels for them.

So how are we going to achieve this? Joe and I certainly don't want people to become seriously ill from eating a Killer bar but, let's be honest, you're already eating similar products. By buying one (note, all revenue from sales is being donated to charities that support healthy eating), you're sending a clear message to the Government that it must act.

Will this work? We'll find out after we launch the product today. See what happens next via the updates included in the show when it's broadcast next Monday.

• The Killer bar is available from killerbar.co.uk (£2.75, plus shipping).
• Joe Wicks: Licensed To Kill will be shown on Channel 4 at 8pm next Monday.