Let's start with the health lobby. There seems little doubt that, as a race, we are fatter than we used to be and that, through diabetes and other illnesses, that is costing health services a huge amount of money.
Even more importantly, the quality of people's lives is being reduced as, in some cases, are their energy levels and their ability to achieve fulfilment. Everyone agrees that it's a bad thing and it should stop. The question is, of course: "How?"
Some of the answers are fairly easy. The food industry can be forced to cut down the sugar in some of its foods, to change advertising styles and place warnings on packaging.
Big business is a soft target because it doesn't have many votes. The politicians then can pass a regulation or two, claim that something has been done, pat themselves on the back, retire to the bar for a few drinks and reflect on how odd it is that the chairs have begun to shrink.
Tightening up on the food industry will help but we need to go further and to promote a healthier lifestyle. More sport: healthier food. To some extent sport can be encouraged through better facilities but, to make a real change, something bigger is needed. We need healthy lifestyles to be in fashion and for slobbing around on the sofa in front of the television all day to be frowned upon.
After all, that is how it was done with smoking. Yes, there were new rules and those rules drove public awareness, but the real turning point was when people began to see smoking as dirty and disgusting and to bring peer pressure to bear on their friends and relations to give it up.
To impel people towards healthy living we need to engender something similar - to keep yourself healthy has to be regarded as a good thing, and a healthy lifestyle praiseworthy.
The charming woman you are talking to at a cocktail party needs to frown when she sees you reaching for a third canap, so that you decline it, saying: "No, I really wasn't going to eat it, I was just straightening it" - a bit like a chess player who has just seen the danger of the move he was about to make.
So there we have our first tectonic plate. The bossy people from Hampstead and Highgate will frown on unhealthy eating and living and, of course, that on which they frown soon becomes politically incorrect.
The second tectonic plate is the anti-discrimination lobby. High on their successes in combating racism and sexism, they are looking for more subjects for political correctness and fat-ism is next on the list. Discrimination against people who are fat should be outlawed. Jibing at them is unacceptable ... well, it is certainly bad manners and, anyway, insulting words or behaviour likely to cause violence are already an offence if in public.
What, though, about this quote from Professor Jane Wardle, co-author of a report on fat-ism earlier this year: "Everyone, including doctors, should stop blaming and shaming people for their weight, and offer support and, where appropriate, treatment."
Fine on the face of it but a little hard to combine with a campaign designed to promote a healthy lifestyle and, presumably, disapprove of the other sort.
Just how would this sort of conversation translate to the playground and how would you instruct your child to influence its friends with weight problems without straying into something politically incorrect?
Before sinking into ever more subtle rules, it might not be a bad thing to apply some common sense. Whether a statement should be regarded as offensive not does not depend upon its content but upon its intention.
Many a wife chides their husband to lose weight as part of a loving relationship. The words "my goodness you have got disgustingly fat" may be quite acceptable there. Use them to greet a foreign dignitary and you probably have a war on your hands.
Finding a way of promoting healthy lifestyles while avoiding fat-ism is likely to be beyond the wit of most of us. Being the lazy people we are, we will all soon give up and simply avoid the subject, which will gradually become taboo. Any improvement in the public health will be restricted to what can be achieved by bullying sweet manufacturers. Meanwhile, we all will get fatter and fatter. But never mind - we will all be wonderfully politically correct.
-John Watson is the editor of the UK weekly online magazine The Shaw Sheet - www.shawsheet.com - where he writes as 'Chin Chin'.
