Newsletter #153: Why Cold Food Might Make You Eat More 🍦
Welcome, as always, to the latest edition of the humanOS newsletter! I hope y’all are having a nice spring so far. I’ve been trying to take advantage of the nicer weather to rebuild my aerobic conditioning, which took a bit of a hit due to the pandemic...and I’ve got a long way to go (to say the least). But, you gotta focus on the process, right?
This week, we examined some new research on diet and obesity, a topic that we often revisit but that is super important.
We learned that eating cold foods/drinks might not be the best strategy if you’re trying to manage your weight (though your mileage may vary), and you certainly will want to curb your consumption of so-called ultra-processed foods. We also got a little insight into what’s going on deep inside the brain in the early stages of childhood obesity, which hopefully will lead to some useful therapies.
To learn more, scroll down 👇🏼
This Week’s Research Highlights
🍨 People may be inclined to eat more when they are consuming cold foods or beverages, as opposed to hot.
Researchers performed a series of studies to determine how the temperature at which foods and beverages are served impacts consumers’ “complementary purchases” - meaning additional foods and beverages bought with the meal, like chips or cookies. For example, they examined customers’ orders at a café in New York City that served sandwiches that can either be served hot or cold (n = 123). The researchers observed that when customers ordered cold sandwiches, they were more likely to get complementary food items with the meal. Similar choices were found at a café that offers hot or cold beverages. When customers bought cold beverages, they were three times more likely to also get some food items like muffins or croissants. But what explains this phenomenon? Previous research suggests that people believe that hot foods and drinks are more satiating than cold counterparts, and this influences their purchasing decisions. There are a couple of aspects of hot food that may sway these expectations. According to the authors, “The literature suggests that the serving temperature of food and beverages impacts aroma and flavor intensity and perception. Generally speaking, as the temperature of food increases, fats melt and enhance flavor and aroma release. As a result, the sensory attributes are more salient for hot foods compared to cold foods.” Along with this amplified sensory stimulation, hot foods tend to be eaten more slowly, and this may help hormones associated with satiety to kick in and make you feel full.
🍟 Higher consumption of ultra-processed food is associated with greater risk of obesity, and specifically with greater age-related visceral fat.
Ultra-processed foods are industrial formulations of substances derived from foods, which typically contain cosmetic additives and relatively little to no whole foods. Basically, anything that you think of as “junk food” is likely to meet these criteria. A couple of recent studies examined how these types of products affect body composition (unsurprisingly, it’s not good!). In one study, researchers analyzed data from a large cross-sectional nutrition survey in Switzerland (n=2057). Dietary information was collected and food items were categorized using the NOVA food classification system. They found that a higher intake of ultra-processed food (as a proportion of total food weight) was strongly and dose-dependently associated with excess body mass in women. Women in the highest quintile of ultra-processed food intake had more than three-fold higher odds of obesity. But of course, “weight” doesn’t tell the full story. How do these foods affect body fatness, and specifically where that fat is deposited? A similar study examined a subsample of older participants in PREDIMED-Plus (n=1485). Consumption of ultra-processed foods was evaluated at baseline, at six months, and at twelve months using the aforementioned NOVA system. However, this study also measured body composition objectively via DEXA. The researchers found that higher intake of ultra-processed foods was associated with greater age-related visceral and overall adipose tissue accumulation in a dose-dependent manner.
🧠 Greater density of cells in the nucleus accumbens is associated with obesity in children and predicts future weight gain.
Prevalence of obesity in children and adolescents worldwide has quadrupled over the past four decades. Because obesity in childhood is a strong predictor of obesity in adulthood, we need to better understand mechanisms within the brain that drive overeating and weight gain early in life. To that end, researchers analyzed data from child participants in a large NIH-funded study. They looked at diffusion magnetic resonance imaging (dMRI) to take a close look at microstructures within the brain and to estimate the degree of cellular density in specific structures, and combined these findings with waist circumference measurements at baseline and one year later to figure out how differences in the brain might influence body composition.
The researchers determined that higher density of cells in the nucleus accumbens was associated with larger waist circumference, and density of cells in this region also predicted increases in waist circumference and BMI one year later.
The nucleus accumbens is a key reward center of the brain that has been implicated in unhealthy eating behaviors. Animal research suggests that unhealthy diets drive inflammation in the brain, which increases the density of cells in the nucleus accumbens, which in turn results in compulsive eating in these animals.
You can see how this might contribute to an unfortunate vicious cycle, wherein unhealthy food leads to neuroinflammation, which reinforces further unhealthy food consumption. Fortunately, animal studies also point to something that may help restore healthy function to the nucleus accumbens: aerobic exercise. For more info on the role of neuroinflammation in the etiology of obesity, and some things you can do about it, check out this past talk from Dan. 👀
Question of the Week
🤔 Most of us had to make some changes to our exercise regimen due to the pandemic. Did you learn anything useful from this challenge, that could result in lasting alterations to how you approach physical activity?
Videos We Loved This Week
- Kevin Hall: Carbs, calories, or quality: What matters most for weight control? Via Obesity Canada.
- James Hill: National Weight Control Registry - Common behaviors in weight maintenance. Via Obesity Action Coalition.
- Mikael Ryden: The role of adipose tissue in weight loss and weight maintenance. Via EASO Obesity.
The humanOS Bookshelf
The End of Overeating by David Kessler.
Why do so many of us eat beyond our physical needs? In this book, former FDA commissioner David Kessler documents how lifestyle changes and constant exposure to hyper-palatable foods combined to fuel one of the largest-ever public health crises of the modern era. This book is about a decade old, but the content holds up remarkably well, and it is a very accessible introduction to the science of food reward and the background behind the obesity epidemic.
