Newsletter #243

I could, of course, include all of them here, but that would make this newsletter pretty long and unwieldy, which is very much the opposite of what we’ve been trying to achieve here. So, I think I'm going to go ahead and split this into two parts.

Without further ado, below are our favorite 2022 studies, 10-6. 👇🏽

It is well established that ultra-processed foods are associated with weight gain. One underappreciated element that may play a role here is texture — processing tends to make foods softer, which in turn speeds up eating rate. This matters because a ton of research has shown that faster eating rate is associated with greater total energy intake. To explore this phenomenon more rigorously, researchers in Singapore had participants (on four different occasions) consume four different all-you-can-eat meals: “soft minimally processed,” “hard minimally processed,” “soft ultra-processed,” and “hard ultra-processed.” The soft ultra-processed meal, as you might expect, was consumed the fastest and led to the highest total energy intake. But when comparing all the meals head-to-head, food texture seemed to be the most important factor in eating rate as well as energy intake. In fact, the soft ultra-processed and minimally processed meals were both consumed faster than their hard counterparts, and subjects consumed more total calories (21-26% more) when eating both soft textured meals, regardless of processing. The researchers conclude that ultra-processed foods lead to greater energy intake due in large part to their texture. Incorporating more hard-textured foods, along with less processing, could be a useful lever for weight management.

Over the past year, we have developed a much greater awareness for the pernicious effects of air pollution. Perhaps most alarming is the effects of exposure to particulate matter on brainpower; one study of a large French cohort found that even relatively low levels of air pollution were associated with significantly poorer cognitive performance. To examine how indoor air quality affects work performance, an international team of researchers recruited 302 healthy office workers in 43 urban commercial buildings located in six countries. The participants’ workspaces were outfitted with real-time environmental sensors, which were used to collect data on indoor CO2 and particulate matter levels over the course of 12 months. Concurrently, the research team assessed the cognitive function of these subjects by having them perform the Stroop color-word test and addition-subtraction test via an app during regular work hours every week. When the researchers analyzed the data, they found that higher concentrations of fine particulate matter and CO2 were associated with slower response times and reduced accuracy in the cognitive tests, and performance deteriorated as concentrations of pollutants increased. Importantly, these effects were evident at levels that are commonly observed in indoor environments. Lead author Jose Guillermo Cedeño Laurent said, “The findings show that increases in PM2.5 levels were associated with acute reductions in cognitive function. It's the first time we've seen these short-term effects among younger adults.”

Blood donation is typically characterized as an act of true altruism. However, new research suggests that it can also confer cardiovascular benefits to the person donating blood, potentially through removal of iron and persistent environmental contaminants that bind to proteins in blood. To examine its impact on the latter, researchers in Australia recruited firefighters with elevated serum levels of perfluoroalkyl and polyfluoroalkyl substances (PFASs). These synthetic compounds occur in lots of industrial and consumer products because of their resistance to fire and water. The firefighters were randomly split into three groups: 95 were assigned to just be observed (controls), 95 were assigned to donate plasma every 6 weeks, and 95 were assigned to donate blood every 12 weeks. After 12 months, the firefighters who donated blood or plasma showed a significant reduction in PFASs. Donating plasma was most effective, resulting in a ~30% reduction in the body burden of PFASs after 12 months.

We have known for some time that eating later is associated with obesity, but underlying mechanisms have been unclear. This is probably the most rigorous study exploring this link to date. Researchers at Brigham and Women’s Hospital recruited 16 participants and admitted them to the lab on two separate occasions, which were separated by a washout period of 3-12 weeks. During each stay, they spent six days in the laboratory, where their nutrient intake, physical activity, sleep, and light exposure were carefully monitored and controlled. The one major difference between these lab stays was food timing: in one protocol, participants ate their three meals earlier (first meal was one hour after waking and last meal was about 6.5 hours before bedtime) and in the other protocol, they ate identical meals later in the day (first meal was around 5 hours after waking and last meal was about 2.5 hours before bedtime). When the participants ate later, waking levels of leptin, a hormone that signals satiety, were 16% lower and they reported increased hunger, compared to when they ate earlier. Their energy expenditure was also lower in the late eating condition: participants burned ~60 fewer calories per waking day (–5% less).

It is often recommended that physical activity be spread out across the week, but obviously for a ton of us that’s hard to pull off, and indeed lack of time is one of the most commonly cited barriers to exercise. As a result, a significant number of so-called “weekend warriors” compress all of their exercise into one or two (usually consecutive) days. To examine whether this pattern of physical activity is similarly health promoting, researchers analyzed data from a large nationwide prospective cohort study including 350978 American adults who reported their physical activity in a survey between 1997-2013. Participants were followed for about 10 years, and the researchers divided them into groups based on their activity patterns: weekend warrior (1-2 sessions/week) or regularly active (≥3 session/week). Initially, the regularly active participants had a lower all-cause mortality than the weekend warriors. However, when the researchers adjusted for total amount of moderate-to-vigorous activity, their all-cause mortality was similar. The key takeaway here is that how your activity is distributed probably isn’t super important after controlling for duration and intensity. It is also worth noting that for people with major risk factors, more frequent physical activity may confer greater health benefits, because some of the beneficial effects of exercise on cardiometabolic markers are relatively short-lived.

🍆 In Japan, dreaming of an eggplant is traditionally thought to herald good fortune in the New Year.

If you wanna learn more, check out our past interview with James Clear (one of my all-time favorites), and definitely give the book a shot if you would like to jump-start those New Year’s resolutions. I always plug this book around this time of year because it’s just that good.

Enjoy the New Year, and we look forward to continuing to share health science with y'all in 2023 🍾

https://mailchi.mp/humanos.me/newsletter-243