The sugar tax was the most crucial Budget announcement

It feels a long time since last week’s controversial budget, given the firestorm over disability benefits and hubristic resignation of one minister. Yet there was also a soupçon of excitement over the announcement of a sugar tax. “I’m not prepared to look back at my time here in this Parliament, doing this job and say to my children’s generation ‘I’m sorry. We knew there was a problem with sugary drinks. We knew it caused disease. But we ducked the difficult decisions and we did nothing’,” said the chancellor George Osborne.

Downing Street was nervous of being accused of hitting ordinary people and there were instant shrieks of “nanny statism”. But this moment was important: a small step forward in the fight against obesity, an affliction that costs the struggling NHS more than £5bn a year. This is a progressive tax, with a two-year delay for makers of fizzy drinks to lower sugar contents below thresholds with higher duties. Obesity hits the poorest in society hardest; pupils leaving primary school are twice as likely to be overweight if coming from disadvantaged backgrounds than those from more prosperous families.

Celebrity chef Jamie Oliver deserves credit for campaigning on this issue. Naturally he celebrated, dancing a jig of delight and going on Instagram to hail a “profound move... bold, brave, logical and supported by all the right people”. Yet the scale of the challenge facing society was highlighted inadvertently by the same chef with his recipe in a Sunday newspaper for an alluring rhubarb and custard pavlova. Each serving contained 56.1 grams of sugar, which at more than 13 teaspoons a portion breaches daily adult intake recommended by the World Health Organisation.

Yet governments around the globe seem impotent as their citizens get fatter. According to a landmark study looking at obesity over three decades published by The Lancet, not one of the 188 nations studied managed to turn the tide on this epidemic of overeating and under-exercising. Despite the fuss, the imposition of a moderate sugar tax should be only the first small step in a struggle that will take decades; its real significance lies in the hope that this is the first move in a sustained war on the food industry, retailers, advertisers and others feeding the addictions.

According to government advisers, 20 per cent of sugar in processed food could be eliminated over five years without consumers even noticing. Sometimes the state needs to nanny, as we saw in the fight to stop smoking. It took decades to change attitudes. Now it seems incredible to recall times when trains were filled with smoke and manufacturers pushed lethal products by sponsoring sports events. Yet although rates have more than halved over 40 years, almost one in five British adults still smoke despite an intensive barrage of public health warnings and high taxes – although only five per cent of our teenagers have picked up the habit.

The wretched Brexit referendum led to the postponement of the rest of the prime minister’s anti-obesity strategy. Whitehall is still debating finer details, with ministers worried about stigmatising fat people, but it is likely to range from stricter advertising restrictions through to controls on food contents and greater emphasis on school sport. No doubt these mild measures will provoke more outcries over ministerial meddling, encouraged by the food industry; in New York, the mayor was forced to back down on efforts to limit sugary drink sizes. We must hope the government ignores any pressures given the importance and urgency of this issue.

Last year I visited sprawling Oklahoma City to meet a Republican mayor who declared war on fat in a city without a single bike lane. He told me how he challenged fellow citizens to collectively lose one million pounds. Then he took on car culture by redesigning urban spaces to encourage walking and cycling, built superb new sports sites and unleashed experts to promote better lifestyles, targeting the poorest areas. People even voted for higher local tax to fund his crusade. Yet even these impressive efforts managed so far only to slow the rise in obesity, not curb it.

A study by McKinsey Global Institute analysed 44 interventions being attempted around the world such as portion controls, subsidised school meals, better labelling, advertising bans, healthy eating campaigns, more use of surgery and redesigning of cities. The authors concluded that if all of the measures were deployed at decent scale in Britain then one-fifth of those currently overweight would return to normal weight, saving the NHS about £1bn a year.

Osborne stirred up a small fuss with his sugar tax on fizzy drinks. But it is only a sweet first step in a bigger struggle to restrain Britain’s bellies. Ultimately, the nation needs a far more intensive mix of nannying and nudging if we are to even think about defeating the modern curse of obesity.