Junk Food, Metabolic Rate, and Inflammation
Hey y’all! Since we are getting pretty deep into the feasting season, when a lot of long-term weight gain seems to actually occur, I thought we’d take a look at a couple of new studies examining yet another way that ultra-processed foods might sabotage efforts at losing weight (or keeping it off in the first place. Given the ever-growing dominance of ultra-processed foods in the US food supply — now constituting 57% of caloric intake on average — this is a serious concern.
It has been suggested that one reason why ultra-processed food leads to weight gain could be due to a decrease in resting metabolic rate (RMR), although why this is the case is not entirely clear. And on the opposite end of the spectrum, foods that are higher in dietary fiber and phytochemicals may lead to a rise in RMR.
One reason could be differences in thermodynamic efficiency. One small trial found that postprandial energy expenditure for a sandwich made from ultra-processed ingredients was 50% lower than for a sandwich made from “whole” ingredients, despite containing the same number of calories and the same macronutrient composition. That could certainly add up over time.
Two new cross-sectional studies, discussed below, also point to inflammation as a potential mediating factor here. A number of studies have shown that ultra-processed foods lead to greater secretion of cytokines and inflammatory factors, and these studies suggest that the inflammatory potential of our diet could also affect our metabolism, for better and for worse.
This Week's Research Highlights
To gain some insight into mechanisms that might underlie a purported association between ultra-processed food and resting metabolic rate, researchers in Iran recruited 285 healthy women with overweight and obesity. They performed bloodwork to assess various inflammatory markers, measured the womens’ resting metabolic rate via indirect calorimetry, and captured their dietary habits using a validated food frequency questionnaire. After adjusting for confounders, they found that higher ultra-processed food intake was associated with a lower resting metabolic rate. When they looked at the subjects’ bloodwork and adjusted for inflammatory markers, such as hs-CRP, this association vanished, suggesting that the link between ultra-processed foods and RMR was mediated through inflammation (why precisely that would be the case, on a molecular level, remains to be elucidated).
🌱 Eating a diet made up of more foods rich in phytochemicals is linked to a higher resting metabolic rate.
Phytochemicals are natural bioactive compounds found abundantly in whole plant foods (and notably are often extracted from ultra-processed foods through refinement). These compounds have also been shown to modulate inflammation as well as energy expenditure. To better understand how they might influence metabolism and inflammatory markers, Iranian researchers from the same team referenced above recruited 404 women and put them through a fairly similar protocol. They measured resting metabolic rate and various blood-borne biomarkers, and analyzed the proportion of calories in their diet that came from phytochemical-rich foods (the Dietary Phytochemical Index or DPI) through food questionnaires. They split the women into two groups based on their RMR per kilogram. After adjusting for various potential confounders, they found that women with a high DPI had nearly 3-fold greater odds of having a high resting metabolic rate. When inflammatory markers were included in the model (in other words, treated like confounding variables), the association disappeared — once again suggesting that inflammation was mediating this relationship.
Random Trivia & Weird News
An entrepreneur named Takeshi Okawara opened a KFC in Nagoya in 1970, but initially struggled to drum up business.
However, he eventually came upon the idea of promoting fried chicken as part of a traditional Christmas feast, and began offering chicken and sides in Christmas-themed party barrels. When he was interviewed by a public broadcast service, he was asked if KFC for Christmas was a custom overseas, and he (falsely) said that it was.
By 1986, there were 600 locations in Japan, and Okawara became CEO of KFC Japan as a result of his clever (albeit not entirely honest) strategy.
Podcasts We Loved This Week
• Gyorgy Scrinis: Ultra-Processed Foods, Nutritionism and Current Food Systems. Via Sigma Nutrition Radio.
• Marc Abrahams: Prizes for science that make you laugh, then think. Via Science Friday.
Products We Are Enjoying
We are getting close to the winter solstice, so days are shorter now than any other time of year (mercifully, that trend will start to reverse in a couple of weeks). That means that most of us probably need some added vitamin D. I’m a fan of this supplement because
1) it’s lab-tested so you know you’re getting what the label says and
2) it comes with vitamin K2, which seems to work synergistically with D3.
humanOS Catalog Feature of the Week
Thanks for reading, enjoy the weekend, and we will see y'all next week!