I always assumed ultra-processed means that the food is loaded with preservatives like phosphates or BHT. I guess that's part of it, but maybe the efficiency of digestion should be considered. I remember Ben Krasnow (Applied Science) measured the calories in poop, humans are not very efficient at extracting all calories leading to very likely large efficiency variance between foods. But extending this further, the calories lost during preparation should be accounted for...

So how about: calories * digestion-efficiency - calories you personally need to expend to prepare or acquire it. The higher this number, the more processed is the food. So cane sugar is very bad, unless you personally harvested it.

Bad news for highly paid programmers.. basically all food should be considered ultra-processed since no physical labor was needed to acquire it.