I can't claim to have done an 800 calorie diet, as my target was 800 to 1200 a day.
This was due to a commitment to work, and advice from the gym club not to severely restrict my diet when exercising.
But the base target was 200 calories for breakfast, 200 for lunch, 400 in the evening.
Ryvita for breakfast, with a bit of reduced fat cheese and maybe ham, or with cottage cheese.
Lunch was a salad, a lot of mixed green leaf, and usual salad type things such as red pepper, onion, maybe a tomato.
Dinner was salad, helped by the hot summer, or some form of beans, and a lot of kale. Mushrooms as well.
Chicken and fish for the meat when I had some.
The odd "snack" was a cherry tomato, if I had gone low after exercise,
Checking my levels very regularly was important.
So, minimal carbs, zero fat, apart from the cheese, and probably the best tip from my dietician was "a rainbow of colours" which does give a good mix to keep all the minerals and nutrients in there.
The other thing I found was flavour was important, so spices in cooked food, fresh herbs, like basil, coriander, oregano, then rocket, cress, all helped in salads.
All small portions, so I can't say I wasn't hungry, but then again, I always was, (which is why I need to lose weight now).
I believe the shakes were used for patients who couldn't eat solids after surgery, but the original diet was designed to wean people off food, then reintroduce good food.
I think I've managed the same lifestyle change, I don't eat bad food anymore, and do tend to keep smaller portions, a lot of veg,
I kept to it, I've lost over 2 and a half stone, my HBA1C is 4.6%, from 6.4%, and my weight is still going down I'm pleased to say.