Sanjay looks at the row of snacks in the supermarket. What will he spend his money on? At last he chooses a packet of salt and vinegar crisps. He tells himself he will save them for later - but then decides to eat just one or two. Then he has a third, and a fourth... before he knows it, the whole packet is gone.

Some people would just call him greedy. But in his book Ultra-Processed People, Chris van Tulleken explains why Sanjay is unable to stop himself. The food industry has spent years making sure he cannot.

The book is about ultra-processed foods - UPFs for short - which are designed to make us long for more and fail to recognise when we are full.

Most everyday food is processed to some extent: butter, for example, has been processed from milk. But UPFs are a different matter. One scientist interviewed by van Tulleken insists we should call them "industrially produced edible substances" rather than food.

They are usually defined as products containing one or more ingredients most people would not have in their kitchens.

Take Pringles, which have 22 ingredients, including guanylate, glutamate and inosinate. These are acids which, in natural food, tell the body that some easily digestible proteinLarge biomolecules made of up amino acids, which in turn are made up of DNA. is coming its way, such as you might get from fish or a meaty soup.

But in their syntheticAn artificial substance or material. It is made by humans using chemical processes, rather than occurring naturally.  form, van Tulleken explains, they trick the body, so that when all it gets is a Pringle - "a sad little ball of potato starch... we find ourselves reaching for another - searching for that nutrition that never arrived".

On average people in Britain get 60% of their caloriesThe amount of energy released when your body digests and absorbs food. The more calories a food has, the more energy it gives your body. from ultra-processed food. This is partly accounted for by takeaways and ready meals, but also by things we eat every day like cereal, ice-cream or cheap supermarket bread.

Chris van Tulleken, who is an infectious-diseases doctor, has a personal interest in this. He has a twin brother, Xand, who until last year was addicted to UPFs - and as a result was 30lbs heavier than Chris. When they took part in a study of twins,¹ no other pair had as big a difference in weight.

As part of his research, Chris van Tulleken spent a month eating UPFs. By the end of it, he writes, "I felt like I'd aged ten years. I was aching, exhausted, miserable and angry".

Defenders of UPFs deny that they are addictive. They say that the extra ingredients make food cheaper to produce and keep it fresh longer, and that well-off people like van Tulleken do not understand how vital this is to families who struggle to make ends meet.

In the 1960s, families in the US spent 16% of their disposable incomeThe money someone has left after paying taxes. on food; by 2021 it was down to 10.3%.

But van Tulleken is not alone. Earlier this year Henry Dimbleby, a food adviser to the UK government, brought out a book on the same theme called Ravenous. He pointed out that 60% of British people are overweight today and 28% are obeseFor adults, obesity is defined as a Body Mass Index (BMI) of 30 or more. A BMI of 25 or more is classed as overweight. - compared to 1% in 1950.

Dimbleby has called for a tax on sugary food and drink, and restrictions of junk-food advertising.

Yes: It is all very well telling people not to eat cheap ultra-processed food - many families cannot afford anything else. That is why British politician Keir Starmer has ruled out a sugar tax if Labour wins power.

No: Eating well is essential. Buying cheap UPFs is a false economy - it is more than likely to lead to health problems such as diabetesA medical condition causing there to be too much sugar in the blood. and obesityThe medical condition of being very overweight. There are many ways of measuring this, including a BMI of 30 or more. (You can work out your BMI by dividing your weight in kilograms by your height in metres squared.) which will make it hard to earn a living.

Or... It depends how you define "well". You can eat healthily for very little money if you cook your own food and stick to simple dishes. A good cook can make delicious food from inexpensive ingredients.   

Protein - Large biomolecules made of up amino acids, which in turn are made up of DNA.

Synthetic - An artificial substance or material. It is made by humans using chemical processes, rather than occurring naturally. 

Calories - The amount of energy released when your body digests and absorbs food. The more calories a food has, the more energy it gives your body.

Disposable income - The money someone has left after paying taxes.

Obese - For adults, obesity is defined as a Body Mass Index (BMI) of 30 or more. A BMI of 25 or more is classed as overweight.

Diabetes - A medical condition causing there to be too much sugar in the blood.

Obesity - The medical condition of being very overweight. There are many ways of measuring this, including a BMI of 30 or more. (You can work out your BMI by dividing your weight in kilograms by your height in metres squared.)