The newest processed food nutrition studies: more to chew on

very processed foods-- pizza, chips fries, etc.

This past Tuesday apparently was Ultra-Processed Food Study Release Day; two studies– one big and one small– were released for the consideration of the Internet. Both of them have bad news about the effects of eating ultra-processed foods: they result in weight gain and contribute to earlier death.

First of all, what is “ultra-processed food”? Yoni Freedhoff, in his Weighty Matters blog, offers two definitions: one fancy, one non-fancy. The fancy one is this:

formulations mostly of cheap industrial sources of dietary energy and nutrients plus additives, using a series of processes

What does this mean? “think of them as the boxes and jars of ready-to-eat and ready-to-heat foods.” Okay. Not that we really need these definitions. As US Supreme Court Justice Potter Stewart said in 1964 about the definition of obscenity, “I know it when I see it”.

Back to the studies. Here’s CNN on the big study:

…the researchers enlisted the help of 44,551 French adults 45 and older for two years. Their average age was 57, and nearly 73% of the participants were women. All provided 24-hour dietary records every six months in addition to completing questionnaires about their health (including body-mass index and other measurements), physical activities and sociodemographics. The researchers calculated each participant’s overall dietary intake and consumption of ultraprocessed foods.

Over the study period, 602 participants died. After adjusting for factors such as smoking, the researchers calculated an associated 14% higher risk of early death for each 10% increase in the proportionof ultraprocessed foods consumed.

This study doesn’t investigate why ultra-processed foods increase mortality risk; maybe it’s the chemicals in the packaging, or other features of the manufacturing processes.

The small study, however, provides some interesting detail for further study. Here are its details, courtesy of Yoni Freedhoff:

[Researchers] admitted 10 male and 10 female weight stable adults as inpatients to the Metabolic Clinical Research Unit at the NIH where they lived for 28 days. They were randomly assigned to either the ultra-processed or unprocessed diet for 2 weeks at which point they crossed over to the other diet for two weeks.

During each diet arm, participants were offered 3 daily meals and they were instructed to eat as much or as little of them as they wanted. Menus were designed to be matched for total calories, energy density, macronutrients, fibre, sugar, and sodium, but differed in the percentage of calories coming from ultra-processed sources.

When consuming ultra-processed food diets people ate on average 508 more calories per day. And not surprisingly given this finding, people gained weight on the ultra-processed diet (1.7lbs in just 2 weeks) and lost weight on the flip side (2.4lbs in just 2 weeks).

He adds, “Wow! That’s huge!” Yes, it is. But you might think, this isn’t surprising. People love junky food, and it’s designed to be addictive. Well, the researchers found that the participants didn’t find the ultra-processed food tastier. They just ate more of it. But why?

Here’s something I hadn’t heard about: the protein leverage hypothesis. The idea is that the participants ate more of the ultra-processed foods because their bodies wanted more protein. The amount of protein they consumed on both diets was about the same (also surprising), but the processed stuff had less protein in it, so they ate more to compensate. Of course they didn’t know this– it just happened. Wow. Here’s Yoni again with more detail:

[The researchers] believe might help to explain up to 50% of the increased caloric intake by way of something called the protein leverage hypothesis which suggests our bodies attempt to maintain a constant protein intake, and so people consuming less protein from ultra-processed foods may be eating more of them to try to maintain some predetermined physiologically-desired/governed protein intake. 

We don’t know if this hypothesis is true, but if it is, that is very very interesting news about human metabolism.

I’m still chewing on this, so more as the story unfolds.

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