Strategic blending can delay hunger.
If you were already imagining that, keep imagining it. Then consider a non-trivial question: Would it be better to eat it as it is, or blend it all together and drink it?
Not many people choose the latter. But among them would be hunger expert Robin Spiller, director of biomedical research at the Nottingham Digestive Diseases Centre in the U.K. And he has data and a deeply considered health argument on his side. Spiller and his team compared the two options head to head in a study, and they found that when people who drank the blended “soup,” it kept them from feeling hungry for about an hour longer than the whole-food meal.
So should everyone be blending everything?
I asked Spiller over Skype as I searched online for used blenders. You can save a lot of money by buying a used blender—especially if you’ve been buying smoothies at one of New York’s fad smoothie shops. It’s tough to walk two blocks in Manhattan or Brooklyn without passing one of these places. Ten dollars gets you half a banana, a scoop of peanut butter, a cup of almond milk, and ice, all under the pretense that smoothies are a healthy option for the human-on-the-go.
Could that actually be … true?
“All other things being equal, if you took a meal and blended it, you’re likely to feel fuller longer,” Spiller said.
The body is very sophisticated, of course, but initially when you take a meal it’s the size of your stomach that determines how full you feel—regardless of what’s in it. After a bit, when the body has analyzed what’s coming out through the duodenum, it’ll start to take a view on whether what you took had nourishment or not. And if it didn’t, you start to feel hungry again a lot quicker.
“That’s why if you drank several glasses of water, you feel full, but only for about ten minutes,” said Spiller. “Whereas if you took the same volume of soup you’d feel full for a couple of hours.”
Though it was late evening in England when we spoke, he was boiling with enthusiasm for hunger science, pointing to study after study. It’s been known for a long time that if you eat liquids and solids in a mixed meal, the liquids will empty faster than the solids.
This was established decades ago using radiotracers on food, where liquid and solid elements would have different appearances on X-ray images. The technology was quite crude; all you could see was that the food in the liquid phase emptied faster than the solid food. But in the physics department at the University of Nottingham was Nobel Prize winner Peter Mansfield. He developed very rapid sequencing that enabled cine pictures of the stomach using magnetic resonance imaging (MRI). At the time, MRI took ages and wouldn’t be suitable for something that moved very fast, like the digestive tract. But this rapid-sequencing led to—among numerous medical breakthroughs—a new era in smoothie research.
“What we showed is that food separates in layers in the stomach,” said Spiller. Until pretty recently, that was only an assumption. “If, for example, you take a dense material like rice and a glass of water, the rice will sink into the dependent part of the stomach. Then the water will seep out. That means that when you stop ingesting your meal, the size of your stomach will go down much faster than had you mixed the rice and the water up into a homogenous gruel.”
Gravity is important in the layering, as is the position of your body. You will digest [ … ]