... because they are so vile you are too nauseated to eat for hours after.
They should use them instead of those weight loss jabs that make eating so unpleasant.
More seriously, I try to stay low carb so I would be really grateful for tips on how to make green smoothies nice without adding lots of carby/sugary fruits and juices. I mean, most smoothies are ok if you whack in a banana or some apple juice etc but I would prefer not to.