Not very long ago, the question would have seemed absurd. Now it is on the lips of respected scientists; MPs are beginning to talk of “a war on sugar”, and this week even England’s chief medical officer – one of the most esteemed voices in the public debate on health – has said sugar may have to be, like the old enemy tobacco, taxed in order to protect the nation’s health.

There came a time in the evolution of public attitudes to smoking when the doctors had been shouting for long enough that the public was broadly aware of the risks and the only question left for the Government was: what do we do about it?

Some believe we are now at the same point in our attitudes to sugar. Others – largely but not exclusively representatives of the food and drink industry – say the entire debate has been skewed by scaremongering.

More or less everyone agrees that eating too much sugar is bad for you. There is also no doubt obesity is a growing problem which is putting a significant, avoidable burden on the NHS by increasing the rates of diabetes, heart disease and other long-term conditions.

But to what extent is sugar – rather than saturated fats, or salt, carbohydrates or proteins, or any of the other bogey-men of modern diets – the cause of obesity and how much should we worry about it?