Mum Always Said: "Eat Your Greens!"

The world has a 'food problem' - or thinks it does.
In a recent book (July) "Waste: Uncovering the Global Food Scandal", Tristram Stuart says farmers, manufacturers, supermarkets and consumers in America and Europe dump 30-50% of their fresh produce - enough to feed the world's starving six times over.
Stuart makes suggestions on how to reduce food wastage. Here's a basic one: eat your crusts. As this represents 10% of a loaf of bread, biffing it equates to wasting a tenth of a field of wheat.
A harder suggestion relates to eating out. Stuart says wastage is caused by the expectation that every diner must have a choice of dishes, so each dish has to be made in excess. Restaurants could reduce this by requiring diners to choose, a day in advance. The only loss is the expectation of spontaneous choice.
He claims many diners are overwhelmed by the range on a menu anyway, and end up ordering whatever someone else is having. Oh, really...?
Stuart suggests restaurants reduce the portion sizes, while allowing anybody who feels hungry to request "supersize" for free. Hmmm, McRitz...! He points out some restaurants already do this, by offering a discount on empty plates - or a tax on uneaten items, depending on how you view it.
But which restaurant - competing furiously for business - would dare offer smaller portions and reduced customer choice? I guess they'd only do it if consumers demanded it.
The loss of 'freedom of choice': do diners really care that much?