This piece of epidemiological meta-analysis, hot off the press, is doing the rounds at the moment:
Consumption of ultra-processed foods and health status: a systematic review and meta-analysis
It illustrates yet another major error in nutrition research.
There are a few key words which flag a given publication for me as junk. If I see "reward" it signifies that the authors consider that certain foods force re-consumption and that such overeaten food has to be stored as fat. High "reward" overcomes the normal control of metabolism which has existed for millenia. This concept is junk to me.
The second phrase which alerts me is the "caloric density" of food. People really do think that you can trick metabolism in to overconsumption. That people and rats are programmed to (say) eat 100 mouthfuls per day. Put more calories in to each mouthful and you get fat. Another junk concept.
Now we have ultra processed food as the next junk term. Let's play a thought experiment.
Given a saucepan, a cooker, some milk, some rennet and a cheesecloth I think it's quite possible your granny might be able to put together something resembling a casein rich cheese-precursor. Somehow I doubt that she could produce a freeze dried pack of lab grade casein powder, so I think we can consider such a powder to be an ultra processed food component.
Sucrose can be extracted from beets or cane without too much technology but modern sucrose coming out of something resembling the Cantley sugar beet factory in Norfolk might be considered as ultra processed, never mind the smell. So might raw refined corn starch.
If you work at Sigma Aldrich you can take soya bean oil and convert it by an unknown (to me) and undoubtedly very, very clever technique in to tricaprylin, a triplet of octanoic acid molecules attached to a glycerol backbone. I challenge your granny to even extract the soybean oil from the soya beans, let alone convert it to tricaprylin. So I think we can suggest that this interesting oil is more than a little ultra processed.
Mix these components up and supply them to a lab in Japan to feed to some rats. We can merely look at the end weights from this paper:
Effects of Different Fatty Acid Chain Lengths on Fatty Acid Oxidation-Related Protein Expression Levels in Rat Skeletal Muscles
Feed one set of rats on crapinabag, which is about as un-processed as anything fed to a lab-rat ever gets.
Feed the next set on the tricaprylin mix, 60% of calories as this fat with generous casein, sucrose and cornstarch.
A final set can be fed with the same ultra-processed diet as the tricaprylin rats but with the soya bean oil left as soya bean oil.
Which rats get fattest? Okay, soya bean oil it is.
Which rats stay slimmest? Tricky. Whole food crapinabag or ultra-processed synthetic caprylic acid based syntho-food?
Well, I'd hardly be posting this if the ultra-processed food came out badly, now would I?
Here's Table 2
So, "whole food" SC crapinabag fed rats ended up at 239g bodyweight, seriously ultra-processed octanoate based MCFA at 216g, seriously ultra-processed soya bean oil based LCFA at 244g.
It's not the ultra processing. It's the effect on insulin, insulin signalling and the ability to resist insulin signalling when the resistance to that signal is physiologically appropriate. None of which was looked at in the paper, it was about something else.
Of course these are the PUFA levels:
The crapinabag was 11% fat, I think we can assume around just over half of that was linoleic acid, probably with a little alpha linolenic acid thrown in.
The 60% of calories as fat in the ultra processed diets both provided the same ratio of omega 3 to omega 6 but the absolute levels of total PUFA were around 3% for the MCFA fed rats and around 34% PUFA in the LCFA group.
The numbers speak for themselves.
What appears to matter is how capable adipocytes are to say "no" to extra in-coming calories. There are obviously a ton of down stream effects of distended adipocytes. Looking at PUFA combined with insulin shows how they get fat.
I'm the last person to suggest junk made of sucrose and starch are problem free but you have to be very careful of processed vs unprocessed as terminology when applied to foods. It's not likely to be as simple as it looks.
PS tricaprylin is interesting in its own right as it is weird stuff, but today I'm just looking at processed vs unprocessed. I hope no one would suggest that tricaprylin is an un processed food component.