Why not go the whole hog and just dont bother to eat at all till you lose the 3stone?
That is not sustainable, nor is just eating one meal a day. The minute you go back to eating you will put the weight back on - yo yo dieting
The only way to lose weight and keep it off is by making changes that you can live with forever. You have to learn good eating habits, the three meals a day, consuming just the calories your body needs, making the choices that fill you, leaving you not reaching for the high fat, high sugar snack foods
One meal a day and you will reach for the wrong foods for you and wont learn anything. You can easily consume more then the calories you need in one meal and all you are doing is making yourself miserable and hungry and totally food focussed
Cutting white sliced bread is a good idea, too easily consumed. Before I started to lose Id be eating 6 slices a day - minimum - now its a couple of wholemeal pittas a week
Im losing slowly but surely but Im making the changes that I can live with forever. I cant look at a life where doughnuts and chocolate and crisps are going to be forever off the list, I need to be able to incorporate those foods but maintain a healthy weight. So if I do have them, its not the end of the world, its OK cos I know now how balance it out and keep within my calorie needs