Ultra-Processed Foods: Ultra-Toxic or Just Ultra-Tasty?

F. Perry Wilson, MD, MSCE


May 22, 2019

Welcome to Impact Factor, your easily digestible weekly commentary on a new medical study. I'm Perry Wilson.

Processed foods. Wait. Ultra-processed foods. Before this week, I wasn't entirely sure what ultra-processed food even is. Like, pills? Pills that you swallow and that's all the nutrition you need?

No, ultra-processed foods are "cheap industrial sources of dietary energy and nutrients plus additives... and containing minimal whole foods."[1] So, like, Cheetos. Delicious!

And whether you are a fan of the Mediterranean diet, the keto diet, the paleo diet, or—my personal favorite—the "alcohol and salads" diet, you are probably avoiding ultra-processed foods.


Observational data would suggest that you are right. Multiple studies have demonstrated that high intake of ultra-processed foods increases the risk for obesity, diabetes, and even death.

But until now, we didn't have a good sense of causality. Maybe people who eat ultra-processed foods have other problems that we are failing to capture. Differences in socioeconomic status alone could drive much of the observational associations seen.

Now we have a rigorously conducted study[1] appearing in Cell Metabolism of the impact of ultra-processed foods, and the results are fascinating.

Twenty volunteers were placed into a metabolic lab for 4 weeks. There, all of their meals and snacks were provided for them. For a 2-week period (chosen at random) they would get an ultra-processed diet. The other 2 weeks, they would get an unprocessed diet. Here's a comparison of a typical lunch in the two diet groups.


Everyone was given roughly twice the amount of calories they needed to stay in energy balance and told simply to eat at will—eat what they want. The dietitians had their work cut out for them, but they matched the presented food in terms of calorie content, macronutrient content, salt, and even energy density.

With the options on the table, participants ate.

And in the case of ultra-processed food, they ate some more. On average, they ate around 500 calories/day more than they did when presented with an unprocessed diet.


Most of the overeating occurred during breakfast and lunch, not dinner or snacking, which surprised me a bit as those processed snacks look particularly delicious.


And all of those extra calories added up. On average, participants gained about a kilogram on the ultra-processed diet and lost about a kilogram on the unprocessed diet, regardless of the order in which they were randomized.


Now, it would be easy to look at this study and get on the anti-processed-foods bandwagon, but I want to point something out. The reason people gained weight on the ultra-processed diet was because they ate more calories. Here's a scatterplot of the relationship between weight gain and calorie intake.


In other words, this study does not show that ultra-processed foods are toxic or imbued with evil humors or lead to more weight gain per calorie. It doesn't show that large corporations are adding special fattening chemicals to their food products.

It shows, mostly, that ultra-processed foods taste better or are easier to eat or have more "cravability," a word that a close friend of mine recently introduced me to. Most likely, this is why they are "bad" for us: Through feats of science and engineering, corporations have created foods that smack us right in the pleasure centers of the brain, and we continue to eat them even after we shouldn't.

Maybe this is one of those things that if we simply acknowledge, we can avoid.

Or maybe not. This whole commentary is making me hungry.


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