I've done this before with some success. I DID try the supermarket's own brand shakes - but they are significantly different to the Optislim shakes that were used in the Newcastle Trial.
The "own brand" shakes are almost like glue - a very sticky, slimy consistency. I think they do this to convince you that you are at least having a substantial "liquid" meal. :lol:
The Optislim shakes are much thinner in consistency, but much more of a milky type dring - like the ready made (Yazoo, etc...) milkshakes you buy in supermarkets. :thumbup: They all taste LOVELY - but I DID NOT like the hot soups that they make. I think the only flavour shake that I dodn't like was the Honeycombe - it was just too sweet for me. The Banana, Cafe Latte and lemon Cheesecake shakes are absolutely delicious!
The Optislim shakes are around £1.50 each (expensive, I know). But I would not do the Newcastle Diet with any other shake having tried Optislim.
Good luck to you !!!