Duane Mellor, lead for nutrition and evidence-based medicine at Aston University, says nutrition scientists cannot prove specific foods are good or bad or what effect they have on an individual. They can only show potential benefits or risks.
“The data does not show any more or less,” he says. Claims to the contrary are “poor science”, he says.
Another option would be to look at the effect of common food additives present in UPFs on a lab model of the human gut – which is something scientists are busy doing.
There’s a wider issue, however – the amount of confusion around what actually counts as UPFs.
Generally, they include more than five ingredients, few of which you would find in a typical kitchen cupboard.
Instead, they’re typically made from cheap ingredients such as modified starches, sugars, oils, fats and protein isolates. Then, to make them more appealing to the tastebuds and eyes, flavour enhancers, colours, emulsifiers, sweeteners, and glazing agents are added.
They range from the obvious (sugary breakfast cereals, fizzy drinks, slices of American cheese) to the perhaps more unexpected (supermarket humous, low-fat yoghurts, some mueslis).
And this raises the questions: how helpful is a label that puts chocolate bars in the same league as tofu? Could some UPFs affect us differently to others?
In order to find out more, BBC News spoke to the Brazilian professor who came up with the term “ultra-processed food” in 2010.
Prof Carlos Monteiro also developed the Nova classification system, which ranges from “whole foods” (such as legumes and vegetables) at one end of the spectrum, via “processed culinary ingredients” (such as butter) then “processed foods” (things like tinned tuna and salted nuts) all the way through to UPFs.
The system was developed after obesity in Brazil continued to rise as sugar consumption fell, and Prof Monteiro wondered why. He believes our health is influenced not only by the nutrient content of the food we eat, but also through the industrial processes used to make it and preserve it.
He says he didn’t expect the current huge attention on UPFs but he claims “it’s contributing to a paradigm shift in nutrition science”.
However, many nutritionists say the fear of UPFs is overheated.
Gunter Kuhnle, professor of nutrition and food science at the University of Reading, says the concept is “vague” and the message it sends is “negative”, making people feel confused and scared of food.
It’s true that currently, there’s no concrete evidence that the way food is processed damages our health.
Processing is something we do every day – chopping, boiling and freezing are all processes, and those things aren’t harmful.
And when food is processed at scale by manufacturers, it helps to ensure the food is safe, preserved for longer and that waste is reduced.
Take frozen fish fingers as an example. They use up leftover bits of fish, provide kids with some healthy food and save parents time – but they still count as UPFs.
