If you are sugar sensitive (insulin resistant) or you've been on a carbohydrate-restricted diet, you are probably aware of the glycemic index (GI). This is a ranking of carbohydrates by their affect on blood glucose levels. The index is divided into three broad ranges:
High: 70 and above
Medium: 56 to 69
Low: 55 and below
Most fruits fall into the medium to low GI (glycemic index), except watermelon, dates and raisins; however, watermelon actually has a low glycemic load. Pineapples, bananas, apricots and mangoes are ranked medium. Grapefruit, apples, pears, plums, peaches, grapes, oranges, and kiwi are all ranked low on the GI.
The difference between a fruit's ranking on the glycemic index and it's glycemic load is the relative quantity you have to eat to raise your blood glucose levels. For example, watermelon has a high GI, but watermelon is mostly water; therefor, you have to eat more of it to to consume enough fructose to elevate blood sugar.
I've read several accounts of people who went on a regular green smoothie diet who reported no spikes in their blood sugar after eating green smoothies. I will link to their stories below. However, my suggestion would be to monitor how your body responds to green smoothies and see for yourself. I assume that insulin resistance varies from person to person.
It is also true that fiber, which is an indigestible carbohydrate, slows the conversion of the plant's sugars to the glucose our bodies convert to fuel (and fat).
Below is an account from blogger Steve Pavlina, who tracked his blood sugar for 19 days while eating green smoothies.
Below is the story of a diabetic who claims that he was able to reduce his insulin after starting a diet of green smoothies. He said that his blood sugar did rise initially, but it returned to normal within an hour.
Here's a type 2 diabetic named Dennis who also claims blood sugar improvements after starting a diet of green smoothies.
Another similar video from a type 2 diabetic:
Here's a type 1 diabetic who claims an 80% reduction is insulin need after starting a diet of green smoothies: