Eating little, losing nothing

It does take a long time of not eating much for me to lose weight.  Today for example, I had two tablespoons, probably less than 100g (or possibly millilitres) of plain yoghurt plus a peach and a small glass of orange juice for breakfast.  A crab salad, not a whole crabsworth, for lunch and a glass of wine.  For dinner, a small helping of salmon, a spoonful of pasta and some french beans, followed by a couple of greengages.  Oh, and a couple more glasses of wine.  I really don't think that's much, and it's fairly typical of the quantities and types of food I've been eating recently.  Yesterday, for example, we went out for lunch and I had a BLT baguette.  The Sage had a steak and offered me his mushroom, a nice open one.  Once I'd accepted it, he said hopefully that he'd swap it for some bacon.  Since he had an 8 oz steak already, I was surprised that he wanted any more - still, I gave him half my bacon, 1 1/2 rasher's worth.  I ate the salad, the slice and a half of bacon, the mushroom (which was grilled, not fried) and drank a half pint of cider and left all the bread.  I hadn't had anything at all for breakfast.  For dinner, I had most of a fillet of fish, grilled, some baked potato and some sautéed courgettes and tomatoes.  Then I had some ice cream, a small helping.

Really, I'm not eating much.  I'm not losing an ounce though.  Unless I'm saving it all up and will suddenly drop half a stone.  But how is it that some people lose several pounds per week?  I really can't eat less, it wouldn't be healthy.