To the delight of scolds, Boris Johnson has turned rhetoric into action and announced a raft of anti-obesity measures that will be no more successful in diminishing the nation’s bulge than any of the previous gimmicks that have dominated health policy in recent years.

This includes a ban on TV and online adverts for food High in Fat, Sugar and Salt (HFSS) before 9pm, the end of deals like “buy one get one free” on “unhealthy” HFSS food and a new campaign to “help people lose weight, get active and eat better after the Covid-19 ‘wake-up call’’. It is worth mentioning here that HFSS isn’t what you or I would consider junk food: it includes a far broader spectrum of products, from raisins to hummus or cheese, than most people realise.

These are ill-conceived, impractical measures that are almost guaranteed to cost businesses and consumers more

There are countless flaws with the Prime Minister’s new crusade. For a start, it won’t work. There’s a reason why ideas like these have lingered around the Department for Health for half a decade, bouncing from one minister to the next before being put on ice. They’re ill-conceived, impractical measures that are almost guaranteed to cost businesses and consumers more – at least in the short-term – while doing nothing to tackle the “obesity crisis”.

The impact assessment on which the latest measures are grounded amounts to little more than desperate extrapolations that conclude, for example, that a 9pm watershed ban on “junk food” advertising will reduce a child’s calorie intake by 1.7 calories per day – the equivalent to half a Smartie. This is the “science” we’re going to be following this time.

No consideration appears to have been given to possible unintended consequences. Sure, label alcohol to make us aware that drinks can be calorific too. But the change in consumer behaviour that may result – switching from beer to spirits in the interest of waistlines, for instance – may not lead to the best of health outcomes. That’s, of course, if consumers take these imprecations seriously: perhaps they won’t? But then what, other than allowing politicians to press release that they have done something (imposed a cost here, added a regulation there), will the great crusade amount to in that case?

The same shaky evidence is pushed into the public domain year after year and yet, contrary to claims by campaigners and the media, childhood obesity is neither “soaring” nor “spiralling”. The official rate peaked at 19 per cent in 2005 and has hovered between 14 and 17 per cent ever since. Nor are we eating more than our ancestors: on average we all consume fewer calories than we did when rationing was in place. If we all returned to the wartime diet we’d swiftly pile on the pounds.

Further, the burden of “overweight and obesity” on the NHS are often miscalculated. Several government and independent estimates range from £5.1bn to £6.1bn. But these are not based on cost-benefit analyses. According to research from the Institute of Economic Affairs, the costs saved on pensions, healthcare, and other benefits from the 7.1 per cent of early deaths attributable to overly high BMIs are calculated at £3.6bn per year, which brings the net costs on the state of overweight and obesity down to £2.46bn — 2.3 per cent of the 2016/17 budget of the NHS.

Yet there is one important difference this time. Yes, it marks another in a long line of nanny state measures designed to clamp down on our perceived vices. First it was smoking, even though smokers subsidise non-smokers, now it’s obesity, and you can bet gambling will be next in the firing line. Yes, there are few examples of paternalism more flagrant than our Prime Minister losing weight through diet and exercise and then introducing measures which implicitly signal that the rest of us are too gluttonous or lazy to follow suit. He may have spent half a century in blissful Epicureanism, making that daily trade-off between indulgence and aesthetic, but we cannot be afforded the same liberty.

The key distinction is that the issue of being overweight or obese was previously handled with such extreme sensitivity. We were even required to refer to the latter as “living with obesity”. Now, however, the mood music has changed. It’s the obese who are to blame for our high Covid-19 death toll, apparently, because the risk of suffering severe symptoms is increased by a third for those with a BMI over 30. If we don’t all lose 5lbs by Christmas we’ll have in some way harmed the beloved institution the lockdown was designed to protect.

When it comes to obesity our Prime Minister, the self-professed libertarian, has done away with the notion of personal responsibility

Perhaps this is a masterclass in deflection: when the reckoning comes, when furlough is unwound leaving millions unemployed and the government has to navigate its way out of the economic black hole, it can scapegoat the obese. Forget Public Health England’s ineptitude – how it discouraged us from wearing face masks, rejected the South Korean model of mass testing, assured us care homes were safe from Covid-19 – and instead wag the finger at fast-food chains or those who lacked ascetic self-restraint. The irony of course is that PHE was too busy obsessing over nanny state pet projects – such as the £200m a year spent on obesity schemes that did nothing to reduce obesity – to adequately fulfil its primary duty of protecting the public from infectious diseases.

Whatever the justifications behind Boris Johnson’s Damascene conversion we now find ourselves on the cusp of a revolution that formally started with #ProtectTheNHS, in which the needs of the NHS are placed above those of British citizens. Quite naturally something as trivial as, say, what British people enjoy eating comes some distance behind that sacred goal. This puritanism is here to stay, even though over-eating only harms the individual, even though our weight has no bearing on how likely we are to spread Covid-19. When it comes to obesity our Prime Minister, the self-professed libertarian, has done away with the notion of personal responsibility, as well as of the joys of personal pleasure. Something he knows as much about as anyone. Back in 2004 the man who is now Prime Minister said, ‘the more the state tries to take responsibility for the problem, the less soluble the problem will become.’ Nothing has changed except him.