The NOVA system is well reported and has four categories
educhange.com/wp-content/uploads/2018/09/NOVA-Classification-Reference-Sheet.pdf
Group 1 unprocessed or minimally processed
- food that has been harvested/peeled/dried/frozen but basically in natural form
Group 2 Processed culinary ingredients - Oils, fats, salt,sugar, flour etc that you wouldn't eat on their own.
Group 3 Processed foods that are cured/salted etc but still a version of the original food - Bacon, cheese, traditional bread, beer, wine etc (I would call these old-fashioned processed foods as they have been around for centuries, or you could at a push make them at home/on a farm)
Group 4 Ultra processed food - Industrial/factory made food products
All factory made foods, baked goods, drinks, sweet desserts, ready meals, packed mixes etc, factory bread.
It's debatable whether they make you fat directly but they are often lacking nutrition and formulated to make you overeat them, in the way of Pringles.
It's definitely about moderation - a lovely home made cake would be better than a cheap factory made cake but would still be fattening.
But a natural cooked piece of chicken or fish is way better than nuggets or fish fingers.
It's a killer really because to avoid them completely you have to ignore 80% of the supermarket. So realistically it's a case of trying to swing the balance.
Natural yoghurt isn't UPF.
I'm sure some yoghurts like say Longley Farm are better than "Crunch Corner". But even posh yoghurts have starches to thicken them and extra flavourings.