A thick and creamy shake sounds deliciously satisfying, and adding that kind of "mouth feel" to low-fat foods has become a multi-billion-dollar business. But are we really fooled?

Some attempts to get people to eat less of some kinds of thick, low-calorie foods have backfired. People actually ate more when their bodies realized that what appeared to be a high-calorie treat was not.

So scientists have been trying to figure out just what it is that makes us feel satisfied. Is it the thick? The creamy? Or just the calories? It's complicated.

Even a subtle increase in texture can do the trick, according to new research out of the University of Sussex in England. They found that volunteers were able to detect even slight differences in the thickness and creaminess of a yogurt drink with different levels of a thickener, tara gum. It's derived from the pods of trees native to the Peruvian Andes, and is added to ice cream and other foods to make them thicker and creamier.

The volunteers said both thickness and creaminess made the drinks more filling. But when it came to keeping people from getting hungry, they said only the sensation of thickness matters.

Confused? We here at The Salt were, too. So we asked Kari McCrickerd, the lead author of the study, what it means.

The experience of eating has two key stages, she says – satiation and satiety.

Satiation is that feeling of becoming full while eating, until it's time to say "no more."

Satiety, on the other hand, is "how long to we wait to eat again and how much do we eat at the next meal", McCrickerd says in an email. They are, she added, two subtly different, yet related experiences. Only the drinks that seemed thick offered the sensation of satiety.

People may be more sensitive to thickness, she says, because it's less subtle than creaminess, and we have more experience with filling up on thick foods. Hello, mashed potatoes! Creaminess may not be a strong enough signal to convey that message alone. The results were published online in the journal Flavour.

So eaters in search of satiety may want to consider thickness as a source of satisfaction.

Wonder what other gums are thickening up your food? NPR's Eliza Barclay gave the lowdown, from alginates to Xanthan gum.