Stephen Evans is the BBC's Berlin correspondent and presenter of Live Longer Wales: The Shape of Wales.
When I started making a program about obesity in Wales, I came with a plateful of preconceptions – served with a side-order of scepticism.
I was very suspicious of what seemed like a widespread view that serious fatness was a problem largely for poor people. I wondered if there was a bit of snobbery in all of this, with the better-heeled sneering at the eating habits of those they saw as their social inferiors – what is sometimes called the "demonisation of the working class".
On this view, the poor, particularly in the south Wales valleys, were over-indulging on cheap and fattening food, pushed at them by fast-food chains. They were victims of rapacious capitalistic American companies. So ran the argument.
Perhaps the best example of the opinion that poor people really could improve their ways came recently from Jamie Oliver, the television chef and entrepreneur who has made a fortune from his own chain of restaurants.
He cited the "Sicilian street cleaner who has 25 mussels, 10 cherry tomatoes, and a packet of spaghetti for 60 pence and knocks out the most amazing pasta". The implication was that if the poor of Italy could eat well then so could the poor of Wales. It was a matter of effort and education.
So, I wondered, did obesity and poverty go together like fish and chips? It turned out that the answer was more complicated than I had thought.
In Wales, the latest figures (from the official Welsh Health Survey of 2012) indicate that, among the most deprived fifth of the population, 28 per cent are obese compared with 18 per cent in the best-off fifth of the population.
So obesity and poverty do seem connected, but with a significant proportion of the richest also badly over weight (nearly one in five).
And other research indicates that the two thinnest groups are likely to be poor men and rich women. This fits what we see around us – men on the lowest incomes often do physical work that burns off calories while rich women have the greatest economic incentive against obesity (fatness in rich and successful men doesn't seem to be the professional or marital barrier which it might be for high-flying women).
There haven't been many studies looking at links between "class" and weight but one of the few was recently done in Leeds. It showed, according to the leader of the research, that "although the prevalence of obesity is higher than desirable across the whole city, it appears that children living in the most deprived and most affluent areas of the city are at the lowest risk".
Is Cardiff different from Leeds in this respect? The detailed research hasn't been done, but it would be very interesting to find out if middle class areas had more of an obesity problem in children than the rougher parts.
What does seem clear is that obesity is a problem in Wales. All the figures indicate that it's worse in Wales than in other parts of Britain.
But what is far from clear is that it's a problem confined to the deprived parts of the south Wales valleys. And urging the poor to cook more broccoli (or Sicilian mussels) might make everybody else feel better about themselves but it won't get the fat off the bulging bellies of the better off.
After all, Jamie's Italian Burger served nicely on a plate at his chain-restaurant in the St David's Shopping Centre in Cardiff contains 1,033 calories. A McDonald's Big Mac contains 490 calories (figures correct as of October 2013).
Live Longer Wales: The Shape of Wales is on Monday, October 7, BBC One Wales, 10.35pm.