Junk food: you know it's not healthy, but it's so good. And sometimes it's just too hard to resist. Did you know, the scientists have been trying to figure out why junk foods have so much power over us for a while. According to a study published yesterday at the journal Cell Metabolism, it probably has a lot to do with the fact that they're usually packed with both fat and carbs.
The researchers found that the reward centers of our brains are more active when those nutrients are combined in a snack. Mice, for example, can stay trim if they're given either carbs or fat to eat, but they pack on the pounds if they're given the mix of the two. But it was less clear how that plays out in the brain, or how it applies to people.
So neurologists and physiologists in Germany and the US set up a kind of food auction where participants bid for snacks, while the activity in their brains was measured with a fMRI. The calories and the various snacks were either mostly from carbs, mostly from fat, or from a mix of both. And the items were sized so that each category contained the same number of calories, to make them equal from an energetic perspective.
The team also made sure that all the foods were similarly well known and liked in a previous experiment. That way, the group couldn't prize any set of foods over the others. The participants consistently put higher bids on the combo foods, things like chocolate chip cookies and candy bars rather than things like nuts, cheese, or crackers.
This willingness to shell out more for the foods that had both fat and carbs was associated with more of a response in brain regions associated with reward, like the top part of the striatum. The researchers suspect this may be because we have separate reward pathways for fats and carbs, both of which are simultaneously turned on by the combo foods. And they think this like simultaneous reward circuit firing something to our brains, just don't know how to handle.
That actually makes sense if you look at our ancestors. For eons, people mostly ate one food group at a time, like when it became available fatty meat one day, sugary honey or berries the next. They didn't really have the option to do anything else because very few foods are naturally rich in carbs and fat.
Agriculture made it easier to mix nutrient groups and meals, but it still wasn't until the last 150 years or so that we started actually making single food items that contain a dozen or more calories of each nutrient type. So for the vast majority of our evolutionary history, our brains simply haven't had to try to estimate the nutritional value of fatty, carb-filled foods.
Researchers also discovered that were pretty terrible at making such judgments. when they asked participants to guess the calories in the snacks they were bidding on, they kind of failed when it came to the Carbee and combo foods. The researchers even identified a part of the brain called the fusiform gyrus - a long strip that's at the base of our brains - that's important for making these kinds of estimations.
So if we can't have to make calories very well when carbs are involved, and we're getting a bigger reward from those fat carb combinations, that goes a long way to explaining why it's so hard for me to not eat more donuts when somebody brings Donuts into work. I'm not saying I resent you for bringing the donuts in, but it's just hard, ok?
Even when they're not that good I keep eating up. Eventually, scientists may be able to use this information to better understand overeating and obesity. And hopefully, that means they can come up with ways for people to make better food choices, even when they're surrounded by lots of junk, as we so often are.
Our next topic weirdly enough, it's about one of those rare natural foods that's rich in the carb and the fat department. African baobab trees produce fruits that have a starchy pulp and a fatty seed. So in a way that makes them like kind of a proto junk food, except that they're also packed with fiber and protein, so they're pretty healthy. The problem is, a new report out this week in the journal Nature plants found that many of the biggest and oldest baobabs - some of which have been feeding people for thousands of years - are inexplicably dying out.
The international research team surveyed 60 trees across the globe, checking on their health, measuring their size, and taking wood samples to estimate their ages. Why you might think that you could just like count the rings like other trees, baobab can grow more than one trunk throughout their lives.
These sometimes fuse together, creating what looks like one big trunk, but inside there are open spaces. And this complexity makes it really hard to date them - the baobab structure is so wacky that rings don't tell you very much. So the scientists relied on a special type of radiocarbon dating instead.
In this method, you use a very small sample from multiple parts of the tree, and count the number of all the different types of carbon atoms, which can then give you a date estimate. The team found that many of the trees were more than a thousand years old, including one that was nearly 2500 years old, making it the oldest flowering tree on the planet.
But in a horrible and unexpected twist, they also discovered that nine of the thirteen oldest trees and five of the six biggest trees were dead or had at least one trunk that was dead. And those deaths all happened within the last 12 years. Scientists aren't sure why this is happening, although they suspect climate change might be to blame.
With warmer temperatures and more droughts, the trees might be struggling to get enough water to support their large frames. But further research is needed to confirm that suspicions. so now the race is on to figure out exactly what's going on before we lose these iconic trees for good.
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