Robert Lustig explains that whole fruit's fiber feeds your gut microbiome and slows sugar absorption, while juicing removes that fiber and sends unbuffered sugar straight to your liver, where it can accumulate as fat.
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So when you consume fruit, that sugar is not for you, it's for your microbiome. And you have to feed your microbiome or your microbiome will feed on you, right? So when you eat your sugar with its inherent fiber, you are actually doing a good thing for your intestine without harming yourself. When you take that fiber and either destroy it like in a Vitamix or a Breville or a Magic Bullet, right? Or you strip the fiber out completely and now have just processed sugar and put it in an ice cream or frozen yogurt or cake. Now, that is added sugar. It is not buffered by fiber. You will absorb that just as readily as you will every other thing in your diet. And now it will go straight to your liver, lead to liver fat.