KEY POINTS:
Lose weight and save the planet. It has all the hallmarks of a zeitgeist diet book and perhaps a TV series in which I will travel around putting punters on scales, measuring out their porridge for the day, and perhaps changing their light bulbs.
But there is some validity to the suggestion that you can simultaneously shrink your waistline and your carbon footprint.
An extra 50kg of weight carried in your car, for example, reduces fuel economy by around 2 per cent.
Even Richard Branson recently signed up to losing a stone before he takes an inaugural flight on one of the superlight carbon-fibre Boeing jets he has bought in order to save an extra 18kg of CO2. Given that his fleet allegedly produces 7.4 million tonnes of CO2 a year, that's not a hugely rewarding diet.
No, if you want to put some meat on the bones of your dual diet, you will have to make bigger adjustments. Including losing the meat. Steak from a grain-fed cow (and most of the world's cattle are now grain-fed) requires 35 calories of fossil fuel for every one calorie of meat. For the environment, you see, there's no such thing as a free lunch.
US conservation biologist Stuart Pimm talks in terms of the planet's primary productivity (the total plant mass created by the Earth in a given year) and has worked out that humans use about 40 per cent of this (and rising) every year, which doesn't leave a lot for other species.
All of which leads ecologically minded agronomists to plead for dietary sanity. But the foodstuffs most often charged with causing and/or perpetuating the rich world's obesity pandemic have more than a whiff of dietary insanity about them.
They tend to be processed using huge amounts of energy so that, on average, in a Western diet it takes 10 calories of fossil-fuel energy to dispense just one calorie of food energy on to your plate. Then there's the fact that increasingly cheap, fattening foods have their roots in industrial production, which is in turn responsible for disproportionate amounts of soil degradation, chemical pollution, aquifer depletion and increased soil salinity.
Changing the contents of your fridge won't solve all of these agrarian issues, but you can begin to redress the balance.
As Michael Pollan advises in The Omnivore's Dilemma: The Search for a Perfect Meal in a Fast-Food World: "Eat food. Not too much. Mostly plants."
Or you could wait for an eco weight-loss innovation. For example, Lauri Venoy, a Norwegian entrepreneur, is buying human fat from a Miami liposuction clinic (455,000 liposuctions are carried out in the US annually) to be used as biofuel. And if that idea isn't an appetite suppressant, I'm not sure what is ...
OBSERVER
