Different cultures not only eat different foods, they have different beliefs about eating, and both can seem equally bizarre to an outsider. To an American, some Japanese folklore about food is just as implausible as the idea that natto is edible. For instance, we've learned on Tofugu that eating fried eel and melon together is supposedly fatal. In fact you better be careful about being too creative with your eel recipes, because apparently freshwater eel and plum can be deadly as well.
These beliefs aren't all bad news, but I'm also not persuaded that if you're pregnant and you want to have a girl, you should get your husband to eat bananas or that it's good luck if your first dream of the new year is about eggplant (along with Mount Fuji and a hawk, because hey, why not?)
But apparently some of this folklore might not be completely off the mark. The idea that eating eel is good for you in hot weather might actually have some validity: it's high in vitamin B1, which is lost in sweat. And some of it's actually not totally unfamiliar: In just about every country ever, people believe that there's always room for dessert, and that eating that dessert – or another snack – at bedtime makes it even more fattening.
It's curious that these two beliefs are shared by different cultures, including the US and Japan. Are we both equally nuts? Or, just maybe, could this mean that there's something to these notions? This is pretty important to me, because while I could easily go my whole life without eating eel and fried melon together, I eat a LOT of snacks and sweets. I dream about baked goods. I plan my trips to Japan around where I can get black sesame ice cream. So these are vitally important questions.
Well, fortunately for me, and those of you who are similarly obsessed, Japanese science is on the case. And so is Japanese science TV, which really gets the idea of "News You Can Use." For a few years, NHK had a program called the Kaitai Shin Show (translated as The New Anatomy Show) and in the two episodes that I've lovingly preserved via DVR, they examined these two beliefs, with important results for your snacking life.
There's Always Room for Jello, or Strawberry Cream Cake
English-speakers often jokingly say that dessert goes into a second stomach. And in Japanese there's a word for it: betsubara. (It's a combination of "betsu" meaning "other," and "hara" meaning belly, with [h] changing to [b] as it does in the case of rendaku.)
Of course we don't literally have more than one stomach like a cow, but as a metaphor, it sure seems accurate. Even if you're so stuffed that you can't fit one more bite of dinner, somehow, you can still eat something sweet afterwards.
One Japanese gastroenterologist, Shigeki Koyama, realized that he could actually test this belief, and his experiment was re-created for the television show. Two women volunteers got into their hospital pajamas and ate a several-course French chef cooked meal brought in specially for the purpose. A tough job, no doubt, but someone had to do it – as the narrator so wisely explained, "We can only find out if we have special room for dessert if we're full."
One woman raised her hand when she felt full and was led into an MRI machine, where her totally packed stomach was easily seen on the screen. Then, the moment of truth: she looked at a big piece of cake.
The MRI image (reproduced above) clearly showed that the shape of her stomach changed – it became narrower – and started pulsing at the opening to the intestines. Merely looking at the cake was enough to cause the stomach to make more room by pushing food out of itself.
The second volunteer's stomach acted a little differently, but still made room: When she had finished her dinner there was a tiny empty space in her stomach on the MRI, and after she looked at the cake, the image showed that it had gotten bigger.
The Science of Betsubara
Back in the studio, professor Takashi Yamamoto of Kio University explained that it's not the stomach that tells us when we're full – it's the brain. When the stomach is full, blood sugar rises, which makes the satiety center of the brain say "stop eating" (or if your brain is Japanese as the one in the diagram on the show, "Taberuna!") .
So how does just a glance at cake change this? There's another part of the brain that releases beta endorphins, which cause excitement and euphoria – and the desire to eat cake, which, of course, is one of life's most reliable, exciting, and euphoric experiences.
Then, this also triggers the release of dopamine. These chemicals together stimulate the feeding center of the brain, which yells TABERU!, and drowns out the satiety center, which is trying to tell you that you should stop now. What's more, the feeding center secretes orexin, which moves food into the intestines, making room for the cake, exactly as the MRI images showed. Sweets bring out more beta endorphin than other tastes, which is why, say, salty rice crackers don't have the same effect as dessert.
Bad News for the Ladies
Do women really like sweets more than men? Unfortunately there's apparently some truth to this stereotype. Females are more sensitive to beta endorphin than males, so their effect in making you want the cake is stronger. And another study, with rats, showed that when given unlimited access to sugar water, female lab rats would drink twice as much over a 24 hours period as males.
The professor explained that this is due to the fact that female hormones have many roles, including allowing us to put on more fat. Great. Thanks a lot, nature.
Do Bedtime Snacks Make You Fat?
Studying the betsubara effect called for high tech equipment, but the next experiment is so gloriously simple that with enough self-discipline you could do it at home. In a study conducted in 1993, seven women in Okinawa were somehow persuaded to eat the exact same meal three times a day for ten days, at 7:30, 12:30, and 6:00. At the end of the period, all seven had lost weight.
Then, they ate the same meals for another ten days, but now, dinnertime was changed from 6:00 to 10:00. At the end of the second ten days, despite eating the exact same food with the exact same number of calories, all seven women had gained weight.
Bedtime Snacks Vs. Afternoon Tea
This is a pretty mind-boggling result. How could the same number of calories make you fatter simply because they're eaten at a different time of day? An obvious possibility is that going to bed right after eating means you don't get a chance to burn the calories. But that's not it, as Professor Shigeki Shimba of Nihon University explained. It's because there's a protein in your body that controls accumulation of fats in cells, and it varies in amount according to the time of day.
When there's more of this protein, called BMAL1, cells can take in more fat. What the research found is that the amount of BMAL1 is lowest at 3 PM, and four times higher at 11 PM.
So there's bad news and good news. The bad news is that bedtime snacks really are more fattening: that's a time when your cells are going to store more fat from whatever you eat. The good news is: you can have afternoon tea instead! 3 PM is the best time to trick your body into storing the least possible fat from a snack.
Don't Be Ruled By Your Stomach Clock
The bedtime snack habit can be hard to break, because some people say that they need their treat to get to sleep. They're not just whining, according to Shigenobu Shibata, professor of the incredibly cool field of Chronobiology at Waseda University. You can even show the same effect with rats: lab rats were fed at bedtime with an automatic feeder and after a few days, they couldn't fall asleep without it.
Why? You've probably heard that your body has a biological clock, but it turns out, there's actually two: one in your brain, and one in your stomach. Normally they're synchronized, but you can get them out of synch by eating bedtime snacks. Then, as in the betsubara effect, you've got another argument between yelling body parts: The biological clock in your brain is trying to tell you to sleep, but the stomach clock, sure that it's nowhere near bedtime, drowns it out.
Fortunately, it's easy to reset the stomach clock: it's entirely determined by what time you get up and eat breakfast. Bedtime snackers who need the snack to sleep are usually also those who skip breakfast. So, get up and eat a good breakfast and you should be on your way to re-setting the stomach clock and giving up that fattening bedtime treat. And then you can thank Japanese science – and Japanese TV – for your new, svelte, afternoon-tea-eating self.