Did you know that astronauts lose weight in space? Well they do, and we’ve known about it for quite a while, but we didn’t really know why. One possible answer, however, is a bit surprising.

Speaking to Popular Science, Dr Scott Smith from NASA’s Nutritional Biochemistry Laboratory said it might be because the astronauts aren’t eating enough. And why is that? Because the food is floating inside them, making them feel fuller than they really are.

“I think it's that food doesn’t settle the same way it does on Earth, so that the stretching of your stomach – which sends the signal to your brain to say ‘you’re full, stop eating’ – I think that gets triggered faster in weightlessness than it does on Earth,” he said.

Eating enough while in space is important for a whole number of reasons. Not least because being weightless causes you to lose bone and muscle mass – which astronauts try to compensate for by exercising regularly, about two hours a day on average.

They exercise using things like a treadmill on the ISS and a weight machine. Each part of their day is allocated to include time to exercise. But eating is important too, especially things like fish, which include omega-3 fatty acids that can help bone health. And if you don't feel hungry, well, you might not be eating enough.

Floating food can cause other rather gross problems too. If you happen to burp in space, well, it might find its way back up your sphincter.

“When you burp, you’re burping through that sphincter at the top of your stomach,” food scientist Vickie Kloeris from the ISS food-systems lab told The Atlantic. “Burping in microgravity is probably not something you want to do a lot of.”

Astronauts now monitor everything they’re eating on an iPad app called EveryWear, allowing their team back on Earth to tell them if they’re eating enough. The astronauts scan the barcode on their food with the tablet’s camera, letting them quickly record what they are eating.

Meals on the ISS have come a long way since the early days of space exploration, with astronauts eating everything from tacos to pizza. Understanding exactly how our bodies process food in space is important, though, as we eye up missions to more distant locations like the Moon and Mars.

And, well, it looks like our stomachs themselves aren’t that well-suited to a weightless environment. If you ever find yourself in space, just remember, that meal is floating around in your belly – and you might be hungrier than you think.

(H/T: Popular Science)