North America is the land of large, the land of largest, in fact. Everything here is huge-especially the people and their appetites for everything that is bad for them. The physical evidence is overwhelming. A friend from New Zealand, flying from home to Europe via the Pacific Ocean and Canada, got off the plane to stretch his legs in the wealthy oil city of Calgary, near the Rocky Mountains. I asked him for his impressions, hoping to hear comparisons between the Rockies and the Alps of his native land, perhaps a comment or two on the friendliness of local folk, or their penchant for cowboy culture. "Everyone's fat," he said.

My Kiwi friend is right. There is countless evidence for his observation beyond the visual. A story in this week's Toronto newspapers says doctors are alarmed at the growing incidence of Alzheimer's disease-a grim condition that robs people of their memory and ability to think. It used to be something that hit in the twilight of life, a sad but almost accepted decline of the mental facilities to match the physical aging of the body. Now, according to the newspapers, Alzheimer's is appearing in younger and younger people across Canada and the United States. And the reason is obesity. That causes diabetes, which in turn-apparently-damages brain tissue and mental decline sets in. I urge my North American friends to reflect on that next time they stuff a hamburger or a donut in their mouths.

Hey, I'm not making any claims to be svelte here. I carry a few extra kilos around my middle-aged middle, so I too am on the risk list for various fat-related diseases. But there's no escaping the conclusions that North Americans-the most prosperous people in the long history of mankind-are digging their way into early graves with their jaws. The other sad fact is that fat is a class issue here. People from lower economic strata don't go to fitness centres or take up mountain-biking. They eat junk food, not health food.

But the culture of consumption that stuff mouths and bellies with empty carbohydrates, fats and vast quantities if sugar knows no boundaries. The well-off have their own form of obesity-a mindless, status-driven spending habit that keeps them busy, stressed, tired and disengaged while further laying waste to the planet's natural resources. Sound a little extreme? Perhaps, but I don't think so. The United Nations has just released a dire report warning that 30 years of environmental gains in North America are being rapidly reversed by the burgeoning consumer spending habits of the continent's people. In short, we are driving our cars more often, burning far more petrol, living in sprawling, energy-inefficient houses, and taking long-holidays on passenger jets that spread air pollutants more effectively than any of Saddam Hussein's putative weapons of mass destruction.

North America, with less than five percent of the world's population, consumes 25 per cent of its energy-most of that generated from non-renewable sources. Family size here has fallen-the best natural form of birth control being affluence-by 18 per cent in the past three decades. The size of our homes has grown by nearly fifty per cent. The notion of the New Left parties, such as Tony Blair's Labour and Bill Clinton's Democrats, that we can have it all-social justice and prosperity, redistibutive policies and wealth-is being sorely challenged. That's one reason I welcome a right-winger in the White House. George W Bush and Co are nakedly pro-business, anti-labour, pro-consumption, anti-environment, and they make no secret of that. It restores political goalposts that get lost in the muddle of the middle of the road.

But even our politics seem an irrelevance in the face of mounting evidence that our consumption habits are killing us. More criminally, they are damaging everyone else's chances at development. We dig our graves with our appetites, and drag you into them. We have it. We spend it. We consume it. You sniff our exhaust as we speed on by. Oh yes, we may throw a few pennies out of the window. Use them wisely. Don't be corrupt or greedy now. Do as we say. Not as we do.