SCOTLAND is in the grip of an obesity epidemic. Indeed, according to Professor Peter Piot, microbiologist and epidemics expert, the whole world is facing a pandemic, not only of obesity, but also type II diabetes and other chronic diseases.

That we have an obesity problem in Scotland is something we have known for some time. Ross Finnie, chair of Food Standards Scotland, declares it “one of the most serious problems we face in Scotland". Countless medical and nutritional experts have warned us about this. Mostly, blame has been thrown at the door of two factors, our increasingly sedentary lifetime, and our Scottish diet, high in sugar, salt and fat. Up till now the approach by successive governments has generally been to tell us what we are doing wrong: eating too many cakes, biscuits, sweets, chips, burgers and fizzy pop. But the educational approach hasn’t worked. Increasingly, experts are becoming convinced that what is needed is not lecturing, but a change in the food supply, or “the food culture”.

The sugar industry tax proposed by former Chancellor George Osborne in his Budget last year is one of the biggest symbols of that shift. The tax came as a surprise. Some thought that Holyrood would get there first, as Food Standards Scotland in early 2016 had been recommending the Scottish government consider such a tax. Food Standards Scotland not only backs the UK soft drinks industry levy, but adds that Scotland could do more. “A tax on sugar content across other food and drink should be introduced,” says chair Ross Finnie.

But will a tax on the sugary drinks industry have any meaningful impact in the fight against obesity and diabetes?

The answer to that question depends on which nutritional expert or food policy thinker you speak to. Most nutritionists are broadly sympathetic to the idea of a sugary drinks tax. By and large, it’s considered that since sugary drinks offer no nutritional value they represent a straightforward, fairly uncontroversial target. Where there is controversy however, is over whether they will result in any significant reduction in obesity, and whether, even, sugar really is the problem.

Sugar is our latest baddie. The very fact that the tax is a key element in the UK National Childhood Obesity Strategy could easily be read as indicating this single ingredient has now been identified as the enemy. It’s a message that has been driven, too, by the recent wave of anti-sugar books and documentaries, among them Robert Lustig’s much-shared YouTube video Sugar: The Bitter Truth, Jamie Oliver’s Sugar Rush and Gary Taubes The Case Against Sugar, which declares that “sugar is the main culprit” not only in the rise of obesity and diabetes, but a whole range of developed-world diseases, from cancer through to Alzheimer’s. According to Taubes, sugar should be treated like tobacco.

But the links between excess sugar and obesity are still contested. Professor Jill Pell, director of the Institute of Health and Wellbeing at Glasgow University, is among those who does not see sugar as the ultimate culprit in obesity. It is, simply, calories, she says, that are to blame. A study she published in 2016 found that fat was “the main contributor to overall calorie consumption and was much more strongly associated with obesity than sugar”. These results suggest, she says, “that even if the tax is successful in reducing sugar consumption, there will be a lot of people who remain obese because they consume too much fat”.

Nor is there yet, as Professor Mike Lean, chair of Human Nutrition at the University of Glasgow, strong evidence of a link between sugar consumption and diabetes when weight is taken out of the picture.

Around the issue of sugar consumption, though, there are many complexities. Lean, for instance points out: “The evidence says that sweetened drinks do have a small effect to promote greater calorie consumption, especially in children. The problem linking sugar and overeating is not the sugar itself, or the calories in the sugar specifically, but the relentless exposure to extreme sweetness, which alters taste perceptions and leads to people to choose more sweet snacks between meals.”

Obesity meanwhile is a social inequality issue, one that affects those in deprived areas the most. Naveed Sattar, professor of Metabolic Medicine at the University of Glasgow observes: “In Scotland our obesity levels have gone up faster than most other countries, partly linked to us having more deprivation.” In areas of deprivation, he observes, there are more fast food outlets and fewer opportunities to eat healthily.

Sattar echoes the view that calories and fat are the problem: “Most of our excess calories still come from excess fat. And if you eat a biscuit people think, lots of sugar, but actually most of the excess calories are fat, butter and all the other things.”

While Sattar believes a sugary drinks tax is a “move in the right direction”, any hope that it might solve the obesity epidemic is, he says, “wildly off beam”. “What we really need is to somehow encourage the other aspects of the diet – eating far more vegetables, fruits, fibre-rich foods, less of the meats, pies, crisps, biscuits, cakes and fast foods.” He describes a sugar tax as “the first part of the puzzle – but the puzzle has many pieces.”

There is research, however, that has modelled exactly what the impact of the tax might be. Dr Adam Briggs, of Oxford University, was lead author on a report published earlier this year, in the Lancet Public Health, which found such a tax it could potentially save up to 144,000 adults from obesity each year, a one per cent reduction in the number of obese individuals in the UK.

“In terms of a single policy,” says Briggs, “that’s pretty significant.” That impact, he also observes, would be greater on children than adults, with as much as a 10 per cent reduction among boys aged between four and 10.

Briggs explored three possible responses from industry to see how that would impact on the effect: reformulation of the products, price increases to the consumer, and a change in companies’ marketing. Already, in fact, even in advance of the tax, we are seeing drinks companies reformulating. This, Briggs points out, is encouraging because it’s “the scenario we thought would have the biggest effect in terms of health".

The UK is at the forefront in such experiments with sugar tax. A small number of other countries have already imposed some levies, among them Mexico, which is already in the third year of such a tax of 10 per cent per litre on all soft drinks. Before and after figures shows that there has been a reduction in purchases. That shift is also almost exactly the reduction that Adam Briggs’ model would have thrown up. “It’s reassuring that what we’ve been looking at isn’t unrealistic," says Briggs.

However, the UK tax is different from the Mexican one. Rather than targeting the consumer, it targets the industry, and with a two-tier system, with different rates for drinks with higher levels of sugar. Some believe that the UK’s adoption of such a tax could be a tipping point, the start of a wave that spreads across the world, in the same way that the smoking ban did. As Briggs puts it: “Other countries are thinking maybe it is politically acceptable to do this kind of thing. From an international point of view this is quite important. Already the Irish are following suit. New Zealand is talking about potentially introducing it. Some countries in Asia that are. South Africa is quite far down the road. So it’s picking up momentum.”

Often, when sugar or junk foods are mentioned, comparisons are made with tobacco. For instance, Professor Jill Pell says that we need to take what has been learnt in other areas and apply it to obesity. "One thing we know from studies on cigarettes is that taxes can be a very powerful tool in reducing overall consumption; and they tend to have a bigger effect on people with smaller disposable incomes so they can also reduce health inequalities.”

Nevertheless, one of the big questions that remains is how the industry will react. Will soft drinks companies find substitutes that are cheaper than sugar? Could an influx of high fructose corn syrup, hitherto capped in Europe and, take sugar’s place as a lead culprit?

Dr Marisa Wilson of the University of Edinburgh, who heads up a project called Sugaropolis which looks at the history of Scotland’s intense relationship with sugar, is sceptical about the impact of the tax. She is concerned about the effect, following Brexit, of a bilateral trade agreement with the United States which could lead to an influx of high-fructose corn syrup (HFCS). “I suspect,” she says, “the tax won’t have a huge impact on obesity, mainly because, on the supply-side you have a situation where high-fructose corn syrup could very easily replace sugar as a cheap substitute. Sugar is not very good for you, but there might be even more health concerns with HFCS.”

She also thinks there is a lot of hard work to be done in Scotland, since our attachment to sugar isn’t new, but one that we have developed over many generations. “We have to look at the ways that sugar has a meaning for Scottish people, is part of the history here of industrialising and de-industrialising. It’s not just about one person, it’s over generations how families have consumed particular products.”

Sugar-consumption has long had a socioeconomic element. “I would argue,” says Wilson, “that disproportionately the working classes were over-consuming sugar from the very get go.” Even today sugar-intake among children is higher amongst those in deprived areas. A 2008 study in Scotland found children in the most deprived areas of society ate 12 per cent more sugar than those in the least, though other studies covering adults found no difference between areas.

That the sugar tax is not a wonder pill is widely acknowledged. Most involved in food policy and nutritional science see it as just one element in a multi-faceted approach. Ross Finnie of FSS points out: “There is no single ‘silver bullet’ solution, which is why Food Standards Scotland is putting forward a broad range of measures to tackle Scotland’s poor diet.” Among the recommendations are “calls for an increase in healthier options and calorie labelling on menus, promotion of healthier options and a reduction in portion sizes".

The sugar tax, in other words, is just the beginning. “We’ve started with sugar,” Professor Naveed Sattar says, “because it was easy. It was a low-hanging fruit. Excess sugar in sugary drinks is easy – there’s no dubiety, we don’t need that much sugar, we can cut it out. The question is, what next? If sugar alone isn’t going to work, how do we tackle the rest of it?”