OBESITY is in the eye of the beholder. In a survey for NHS Health Scotland, only 29 per cent of participants could identify an obese body shape when presented with computer images of figures gradually gaining weight. It also emerged that many Scots vastly underestimate how heavy a person must be before they are considered obese, and that they don’t realise how their own weight has become a health risk.

This is troubling, even allowing for the somewhat elastic-waisted definition of “obese” that has emerged in recent times. Traditionally, in medical circles, it has meant 20 per cent over ideal weight, which can cover a multitude of sins and sizes way short of the image that “obese” conjures up in many people’s minds.

The waters were further muddied through deployment of the dreaded Body Mass Index, which appeared to find that muscular and ultra-fit rugby players were technically obese. Many a bewildered observer might have been forgiven for thinking: “We are all obese now.”

Perhaps it is time for a new word and a new understanding of the concept. Or perhaps obesity has become so prevalent that the population fails to recognise it any more. If it has become the norm, then we are in trouble. And that’s all of us because the resultant health problems – including cancer, diabetes, heart conditions, strokes, osteoarthritis, infertility, asthma and liver disease – will put pressure on a health service which is having a difficult time as it is.

What to do? Well, you can tell people what to eat but there’s a fair chance that their response might just fall outwith the margins of normal, polite discourse. People have to decide these things for themselves. The trick is to nudge them subtly towards doing what is best for them.

Ironically, while no one likes to be nannied, it has also emerged that most Scots support legislative measures to reduce the levels of sugar, fat and salt in food. That includes a tax on sugary, fizzy drinks, though it was not immediately clear whether, at policy level, they also thought this should apply to Irn Bru in Scotland. Nevertheless, seven out of 10 people agreed that obesity was a problem that had to be addressed.

This is encouraging news. Many people may not recognise obesity when they see it, but most recognise that there is a problem and that something must be done. But by whom? All faces turn to the Scottish Government. It has already pledged to “change our food culture”. Its consultation on tackling obesity is nearing an end, and it has already proposed outlawing multi-buy deals on junk food, confections and high-calorie soft drinks.

In addition, it has sponsored the Scottish Grocers Federation’s Healthy Living Programme, which aims to provide a wider range of healthier items in convenience stores, and has worked with retailers to promote both the Healthy Start Programme and the Fruit, Vegetables and Potatoes Action Plan.

This is all good meat and potatoes stuff, as it were. But we can’t expect the Government to do everything. Ultimately, this is a matter for the individual, giving rise to the classic conundrum of our time: how do the authorities persuade people to take personal responsibility?

Without getting into a philosophical argument about means and ends, practically this entails changing the food environment, taxing the bad stuff, and subtly improving consumer education without hectoring. It means accentuating the positive in healthy food, where pleasure is not foregone … and neither is health.

In this way, perhaps we’ll be able to return to these scenes we’ve all witnessed in black and white pictures from the past, where rare cases of obesity or being overweight or call it what you will were always pretty obvious.