Smoothies, in theory, are pretty brilliant. You can just throw in two cups' worth of spinach along with strawberries, bananas, chia seeds, and voila, that's already half of your daily recommended dose of fruits and veggies in just one drink. Getting lots of nutrients in one easy to consume drink is great. But it doesn't necessarily mean that smoothies are healthy.
A recent New York Times story reports that you are likely consuming more calories and sugar when drinking a smoothie than when eating whole fruits and vegetables. According to a famous dietitian and nutritionist people often overdo it by drinking half a liter smoothies–that's the size of a especially if you're buying from a store that adds loads of sweeteners thereby adding calories.
Even if you make smoothies at home, the way we drink smoothies in just a few minutes as opposed to taking our time eating whole fruits leads to over consumption. The fiber in whole fruit acts as a net to slow down the body's process in converting sugar from food into blood sugar. Smoothies don't eliminate fiber, but they are shredded to bits in the blender and, thus, less effective. You're likely to feel hungrier again sooner after drinking the smoothie than you would have had you eaten the same fruits and vegetables whole.
There's a fine line between a smoothie and a milkshake. The bottom line is eating whole fruits is better than blended fruits. Also, if you were thinking of getting a smoothie anyway...just go all the way and treat yourself self with a milkshake, won't you?