HOW often do you see apples on a bogof (buy one get one free) offer? Or discounts in the supermarket if you buy broccoli and cauliflower at the same time? If you think it always seems to be chocolate biscuits, ready meals and sugary breakfast cereals that are on offer, evidence seems to be on your side.

Perhaps that is why so many Scots backed the idea of a ban on supermarket junk food promotions in a major poll for Cancer Research. A remarkable 69 per cent of those questioned said they would strongly support such a ban.

Some might find it a rather poor reflection on our collective confidence in our own willpower that this result was so convincing. But three out of every five of us believe such promotions encourage shoppers to buy things we wouldn’t have otherwise bought.

There is a precedent for such a public health intervention in the freedom of the supermarkets to charge what they please, of course. The ban on multi-buy deals on alcohol in supermarkets and off licences came into force in 2011, and although not all studies have found it had a major effect, an NHS Scotland study claimed it had cut consumption in Scotland by 4.5 million bottles of wine a year.

Yet some will feel applying the same tactic to junk food is an unnecessary intrusion into the ability of supermarkets to manage their businesses, and of individuals to make their own lifestyle choices.

It would be wrong to say we have not made considerable headway in improving Scotland’s historically bleak health record. But we know that many of our eating habits are bad, and unhealthy choices have a wider impact than the simply personal. Evidence shows strong evidence of a link between excess weight and 11 different cancers, as well as heart disease, stroke, and diabetes. Excess sugar causes tooth decay. These are damaging, often life limiting conditions and increasingly affecting children as well as adults. Public health interventions are worthwhile not just in terms of the personal cost but the very real cost to the NHS.

In that context legislation can play a part, and it is often effective. Given that the survey found one in five Scots drink sweetened fizzy drinks daily, the news this week that drinks manufacturer AG Barr is to cut the sugar in Irn Bru is welcome. It may have been driven to do so primarily by the sugar tax announced in last year’s budget, but that only suggests that the policy is working.

Indeed, the singling out of fizzy drinks for targeting with a tax – questionable at the time – looks increasingly puzzling.

Against the personal liberty argument on such policies, banning promotions would only restrict an individual’s liberty to buy unhealthy foods cheaply, the choice would still be theirs. More seriously, such methods are often argued to act as a “tax” on the poor. This is an unconvincing argument since it implies this group would disproportionately benefit from any resulting health gains.

Cancer Research UK is just one charity calling for a price promotions ban on unhealthy foods. The public appears to overwhelmingly back it. It may be time for governments to seriously consider such a step.