Perhaps the anthropologists will find evidence of a small, but developing group called freegans. Freegonomics is about eating for free in order 'to limit your participation in the conventional economy' - easily done once your friends and neighbours see you lifting food out of dustbins. The richest pickings are to be found in supermarket bins, where you will find huge quantities of food that's been thrown out (many now lock their wheelie bins), but in fact we're all guilty, throwing out a third of our food shopping every year, sending some 17m tonnes to landfill.
If freeganism is a bridge too far, try 'meat reducing' and embrace Meatless Monday, as advocated by the Center for a Liveable Future in the US. Not only does this reduce your saturated fat intake, but it takes the pressure off the planet: the average inhabitant of the developing world consumes nearly 30kg of meat each year (and this is rising quickly), while meat eaters in developed countries continue to chomp through around 80-90kg a head per year.
Any more increase in the 8bn livestock currently covering one-third of the earth's total surface area is inherently unsustainable. Not only does it take just 550 litres of water to produce a loaf of bread (as opposed to 25,000 litres of water to produce eight ounces of beef), but intensive livestock farming also leaves a waste problem of its own, now that industrialised farming prefers the chemical fertiliser option.
The global food industry's response is the April-fools-like 'enviro pig' - genetically modified to produce less phosphorus manure than non-chromosome-altered pigs. Graham Harvey, author of We Want Real Food (£9.99, Constable) and farming consultant to The Archers no less, would prefer a radical overhaul of the global food industry. His research shows that food might be proportionally cheaper, but we're being short-changed, losing crucial micronutrients: 'Over the past 50 years, vegetables sold in the UK have lost 24 per cent of their magnesium and 46 per cent of their calcium.' He advocates buying as natural a product as possible, such as grass-fed beef and lamb - cows and sheep are ruminants and have no business being fed on corn.
But if you're really concerned about portion control, take advantage of the fact that local shops have been squeezed out by supermarkets. The average grocery shop journey is now 4.2 miles, so leaving the car at home will not only limit what you can carry but help you build up a real appetite.