[Disclosure, the lead author, Kevin Hall, is a friend of mine and we co-authored a paper together in the past]A huge deal pre-print paper was published yesterday, "Ultra-processed diets cause excess calorie intake and weight gain: A one-month inpatient randomized controlled trial of ad libitum food intake" that, if its results are replicable and shown to persist over longer time frames, might well explain the rapidly rising weights of the world.
While it has been shown that as food supplies become more industrialized (also referred to as Westernized), weights rise, the reasons why remained unclear. Many have tried to explain away the gains as shifts in the macronutrient composition of a society's diet and depending on the era (or the guru), have pointedly vilified dietary fat, dietary carbohydrates, animal protein, lectins, grains, sugar, and more. Some have done so in part on the basis that when their dietary demon of choice is removed from their adherents' diets, they are seen to lose weight, often even in the absence of tracking calories or anything else for that matter. But common to most of those diets and anecdotes, is their necessitation of forgoing our ultra-processed world and in its place bringing in a great deal more cooking and meal preparation.
Before we get to Kevin's study, here's a basic definition of ultra-processed foods
“formulations mostly of cheap industrial sources of dietary energy and nutrients plus additives, using a series of processes”If you're interested, you can read more about them here. But for the sake of this study, think of them as the boxes and jars of ready-to-eat and ready-to-heat foods.
So what did Kevin and his colleagues do?
They 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.
And the results?
When consuming ultra-processed food diets people ate on average 508 more calories per day. That's roughly a meal worth. That's huge!
People ate ultra-processed foods faster, and the energy densities of these foods are higher and both of these factors likely explain part of the increased caloric consumption, but the other possibility according to the authors might be protein. The ultra-processed diets contained slightly less protein, something that Kevin believes 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.
Now this is just a very brief overview, and there will undoubtedly be deeper dives into this including in regard to the various metabolic parameters measured (including hunger hormones and peptides), but given how significant the findings appear to be, I thought I ought to whip something up quickly and the calorie piece is by far the most striking and most important in the context of it being a unifying smoking gun for global weight gain.
It's also worth noting, and Kevin did so on Twitter and in the paper itself, while the results of this study definitely suggest that markedly reducing or eliminating ultra-processed foods in our diets may well help with our weights, doing so requires a great deal of privilege, time, skill, and expense. The good news though is that there are ample levers in our food environment that would help to do so and are ripe for reform that have nothing to do with the usual lenses of individualized blaming and shaming including:
- Improved school foods and school food policies that reduce ultra-processed offerings
- Bolstering the case for bringing back home economics
- Furthering the calls to ban junk food marketing to children (and adults)
- Changing food culture such that ultra-processed foods aren't the cornerstone of every event no matter how small
- Pushing ultra-processed junk food out of sport and sport sponsorship
- Putting an end to ultra-processed junk food fund raising
- Institutional and corporate cafeterias' offerings' reforms
- Strengthening front of package labeling reforms by perhaps not permitting front of package claims on ultra-processed foods (or adding warnings)
Even more good news is that a focus on ultra-processed food as a whole, especially one coming from a place of causality, is a focus that pretty much every diet cult can get firmly behind.