It might be my body adapting quickly I guess (but it never has done before so I would be surprised), but I have been reading about the need for low GI foods to keep hunger at bay. I decided that Weetabix was the best breakfast I could have (from our current cereal cupboard stash) and 2 bix and 125ml milk is 200cals. A couple of black coffee buckets during the day and then a pot of Kabuto noodles (posh pot noodle), for 309cals (noodles are low GI) and a little zero fat Greek yogurt, 86cals (again low GI) brought me nudging up to just under 600 cals for the whole day (I'm a bloke I am allowed 600 ).
The only other thing I did differently was ride my pushbike 9 miles each way to work and back, but I would have thought that would have made it worse not better.
So low GI really does seem to be the way to go.
Hope that helps
Steve