Turns out, consistency might not only be important when it comes to exercise, but what you choose to drink too. Let me explain: Most mornings, I have a smoothie for breakfast.

Not just any smoothie, but a full-bodied, creamy one. I prefer my smoothie on the thicker side, but sometimes a little extra liquid slips in since I tend not to measure these fluid experiments. And I’m learning that this might make a bigger difference than I thought. A recent Dutch study published in the American Journal of Clinical Nutrition sought to understand the effect that viscosity, or consistency, had on the perception of fullness in participants. They were split into two groups; one drank a thick but low-calorie (100 calorie) milkshake, and the other drank a thinner but higher-calorie (500 calorie) shake.

Then, researchers looked at the stomach contents of the participants as they sat in an MRI machine, and asked them how satiated they felt.

Although the lower-calorie beverages emptied from the stomach more quickly, participants reported feeling fuller: a 58 out of 100 on average compared to 48 for the higher-calorie, thinner shake. What’s going on here? The researchers called this the “phantom fullness” phenomenon: even thought the thin-shake drinkers sucked down a less filling drink, they felt as if the opposite was true. The take-home message: Perception might be more important that physiology—so try choosing a thicker but healthy drink to “fill” you up and shy away from beverages that promise to satisfy you but don’t deliver. We’re looking at you, soda.

Resource: AM Smeets, Paul, Camps, Guido, de Graaf, Cees, Mars, Monica. Empty calories and phantom fullness: a randomized trial studying the relative effects of energy density and viscosity on gastric emptying determined by MRI and satiety. Am J Clin Nutr, 115.129064v1.

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