I've never made my own but I guess it depends how you make them, I have seen many ideas around the internet using various ingredients but what stuck in my mind was in Slimming World group our consultant informed us blended fruit was not syn free. The reason is because fruit still has calories and if blended you use more to make up your shake or smoothie... it was something along those lines. Guess it does make sense and depends on which fruit you use too.
Not much use I'm sure
I like celebrity slim shakes over others I have tried so far.