Monday 1 August 2022 10:33 PM DR CHRIS VAN TULLEKEN: We need health warnings on ultraprocessed food! trends now

A year ago I managed to persuade my identical twin brother, Xand, to forswear ultraprocessed foods (UPFs) such as pizzas, ready meals, crisps and chocolate on which his diet had relied so heavily and unhealthily for years.

UPFs are essentially industrially produced foods stuffed with sugar, fats and strange chemical ingredients that you don’t find in a normal home kitchen.

At one point Xand hit 19 st and that bothered me — not because I cared about how he looked, but because I was worried about what it would do to him in the long term — that he’d die, leaving me to live miserably without him.

So I put him on a sickening binge diet that was 80 per cent UPFs for a week, while he talked to experts about how such products can be addictive and lead to obesity.

What Xand was undergoing was a form of intensive aversion therapy — and it worked well: after just four days he found it almost impossible to eat UPFs.

On the anniversary of that experiment, in a new podcast, I met my brother just before his usual dinner time. I had broken my habit of nagging him about weight but I wanted to see if he could be tempted.

I tried to entice him with cookies and chocolate. He threw the packets across the room in disgust. A year ago Xand would have eaten all of those — followed by a takeaway. Nor was this ‘disgust’ just for show. The contents of his fridge and kitchen cupboards have transformed.

Tellingly, one of Xand’s big UPF moments used to be his flights to Canada to see his teenage son Julian. But instead of the usual airport binge — stocking up on crisps and sandwiches — on his most recent trip, he filled two plastic tubs with a cut-up block of cheese and some apples. Even I was impressed. Xand also looks and seems noticeably healthier.

This was a huge success. But Xand is not the only one whose life has changed since investigating UPFs with me.

Last year, for our BBC podcast, I’d consulted Alasdair Cant, a Cambridge-based behaviour-change expert, who explained I had to stop blaming Xand for his high-UPF ways, because I was causing a state of confrontation where neither of us would budge — and this blocked Xand from making changes to get healthier.

On Alasdair’s advice I changed tack completely. I simply let Xand have all the available scientific information about UPFs so that he could make up his own mind.

I know from my own experience how hard it is to give up UPFs — and then to reverse the effects on your body. Last year, for a BBC documentary, I too lived on an 80 per cent UPF diet for a month.

Extreme though it sounds, my UPF diet (and Xand’s) is what one in five Britons consumes every day — and research incontrovertibly shows that it is the main driver of obesity in this country.

After a month, my 6ft frame ballooned: I went from my normal 13 st to 14 st. The weight has gradually been coming off by avoiding UPFs, but over a year later I’m still around 13 st 5 lb.

I read constant claims that all you have to do to lose weight is to stop eating UPFs, but it’s not that simple — not least because of the damage these foods can wreak.

Disturbingly, during my experiment my brain began to become addicted to UPFs. An MRI scan showed an increase in the connections between the reward centre and areas that drive repetitive, thoughtless behaviour in just one month.

Essentially I’d become wired for cravings and mindless consumption of food; my brain was telling me to eat UPFs without even wanting them. When we repeated the MRI scan three months later, those addictive brain changes were still there.

Such results made me physically disgusted at the changes UPFs wrought on me, and morally disgusted that people actively peddle this stuff for financial gain.