Here’s why, according to registered dietitian Beth Warren:
First: It’s because you’re not chewing anything. Liquid calories mess with the way we register fullness. Because chewing activates part of the digestive process. So if you’re sipping berries through a straw, you won’t have the same feeling of being satisfied as when you actually chew berries.
Also, we can drink faster than we can eat… Again, because there’s no chewing. But when we consume something faster, the brain doesn’t have time to register the “I’m full” signal. So you don’t feel full.