Newsletter #050: Why Exercise Might Not Make You Skinny, Food Coma, & Cauliflower Crackers 🍘
Welcome to the latest edition of the humanOS newsletter! Here is where we share our work, and the various studies and media that captured our attention this week. 🤓
This Week’s Research Highlights
🦠 Alterations in the gut microbiota may cause vascular dysfunction associated with age - and this may be reversible.
Researchers administered broad-spectrum antibiotics to both young and old mice to effectively wipe out their gut microbiomes. After 3-4 weeks, the old mice showed vast improvements in all measures of vascular health. The antibiotic treatment reversed age-related endothelial dysfunction and arterial stiffening, and this was accompanied by reductions in vascular oxidative stress and inflammation. When the team sequenced and compared gut microbiota of young and old mice, they found that older mice tend to have more pro-inflammatory and pathogenic bacteria, and three times as much TMAO (trimethylamine N-oxide), a metabolite linked to cardiovascular disease.
Researchers in China analyzed data from 21 prior studies involving >320000 people. They found that shift workers were 13% more likely to develop cardiovascular disease, compared to daytime workers. For every year spent working on shift work, there was a ~1% increase in risk.
🥗 Food coma (some call it “the itis”) may be related to a rise in circulating cytokines after eating.
16 subjects (8 lean and 8 obese) were randomly assigned to receive either saline (placebo) or an IL-1 receptor antagonist. Antagonism of IL-1 led to a reduction in postprandial fatigue. This effect was more pronounced in obese individuals than lean counterparts. This makes sense - it is known that elevations in cytokines, particularly in the interleukin-1 family, are associated with fatigue in inflammatory diseases. Chronic Fatigue Syndrome, in fact, is associated with elevated IL-1.
Researchers assessed activity patterns in 5638 older women - primarily gauging average daily sedentary time and mean duration of sedentary bouts - then followed their health outcomes for about five years. Women with the highest total sedentary time were at the highest risk of cardiovascular disease. Each additional hour of sedentary time was associated with a 12% increase in CVD risk and a 26% increase in risk for heart attacks. Women with the shortest sedentary bouts had a 54% lower risk for CVD than those with the longest, suggesting that sitting less and regular interruptions in sitting time might help reduce cardiovascular risk.
Researchers collected data on outdoor bright sunlight and temperature, then assessed how it associated with measures of glucose and lipid metabolism in a total of 10226 middle-aged European subjects. They found that increased bright sunlight exposure was associated with lower fasting insulin (-1.27% per extra hour of bright sunlight), lower homeostatic model assessment for insulin resistance (-1.36%), and lower serum triglycerides (-1.28%) in participants of the Oxford Biobank study. No associations between outdoor temperature and measures of glucose or lipid metabolism were detected following adjustment for bright sunlight.
Podcasts We Loved This Week
- Matt Richtel: How to Support Your Immune System. Via The Genius Life Podcast.
- Neil Stanley: Sleep Research Roundup. Via Sleep Junkies Podcast.
Products We Are Enjoying
Ginny says: I got these at Whole Foods last week and I have thoroughly enjoyed them - more than I expected. They have 100 calories for about 40 (itty bitty) crackers, which is decent. And the main ingredient is cauliflower powder, so they are actually pretty nutritious for a cracker. I don’t typically endorse junk food with a health halo (which is kind of what this is), but if you’re looking for something crunchy to munch on while watching Game of Thrones, I think this definitely fits the bill. It does taste like cauliflower, so be ready for that.
New humanOS Content
- humanOS Radio: Studying Preindustrial Societies Informs Us About How to Be Healthy. Podcast with Herman Pontzer.
This week on humanOS Radio, Greg interviewed Herman Pontzer. Dr. Pontzer is an Associate Professor of Evolutionary Anthropology at Duke University. His research focuses on the physiology of humans and apes, and he aims to understand how ecology, lifestyle, diet, and evolutionary history affect metabolism and health. He has done some remarkable studies examining physical activity and energetics in small-scale societies, including hunter-gatherers and subsistence farmers. He is best known for his constrained energy expenditure hypothesis, which is the primary subject of this interview.
So what is meant by constrained energy expenditure? The basic idea is that organisms evolved in conditions of limited energy availability (in the form of food). As a result, animals have evolved mechanisms to maintain total energy expenditure (calories burned) within a range that is aligned with typical food availability in the environment. Makes sense. But here’s why this matters for us: The hypothesis implies that if someone increases their physical activity (and thus ramps up energy expenditure), he or she will not necessarily burn more calories in the long term.
Support for this idea came from a study published by Pontzer and colleagues back in 2012, revealing that the Hadza (a group of traditional hunter-gatherers) burned the same number of calories as Westerners, despite the former being vastly more physically active than the latter. A subsequent study comparing total energy expenditure and physical activity in a large adult sample found that total caloric burn plateaued once it went above a moderate level. So, higher physical activity does not seem to increase energy expenditure in a linear manner, like we have always thought.
So what are we to make of this? What does this mean for people who are trying to lose weight? To learn about Dr. Pontzer’s research, and what else we can learn from preindustrial societies about health, check out this interview! You don’t want to miss this one.