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Why is soup so filling?

It’s been known for generations that soup can be filling - but have you ever thought about why? I mean take the ingredients of soup and have them as a meal - it’s just not as filling as having the soup itself. What I mean is cook a handful of veg (say) and drink a glass of water, and it will be less filling than if you were to cook the veg in the water and blend it down into a soup.

So why?

The answer is in the stomach. In an investigation into this, researchers have found using MRI scans and ultrasound, that after you eat a meal the valve at the bottom of the stomach (phloric sphincter) holds back food so that it can be digested. So with your two meals (the cooked veg with a glass of water vs the veg soup) both are held back to be digested - with the exception of the glass of water which the valve allows to pass straight through. The result is that eating the soup leaves a greater “bulk” in the stomach, which takes longer to be cleared that the veg and water equivalent.

When the stomach empties, calls in the stomach wall release a hormone called ghrelin. This hormone causes you to feel hungry and makes you want to have something to eat. So, by eating soup, you stay “full” for longer, this hormone is delayed in its release by up to an hour and a half and therefore you don’t feel hungry for longer.

A great practical application of this is if you wanted to eat less (say to lose weight). Eat soup.