Last September Weight Watchers changed its name. It had already rebranded, having dropped 600,000 subscribers and shifted its focus to “wellness” rather than diets, so a name change was not a huge surprise. But what was a surprise was its insistence that the new name, WW, doesn’t stand for anything, not even its new tagline: Wellness that Works. It stands for nothing. The company is back in the news this week with the launch of a new diet app for children. Which, well.

There are small cultural touchpoints that when pressed today cause a sort of shudder, as if you’ve found an existential bruise. Certain handbags, for example, or prime ministers. Pete Doherty. Reading Candace Bushnell’s new book I felt one such shudder. Even though the first time round few of us identified with either the Sex and the City archetypes of womanhood or their ambitions of love (distinguished through huge wealth or big dicks) and friendship (distinguished through aspirational brunch items), we understood their mainstream appeal. Today Is There Still Sex in the City? with its reductive acronyms and designer vaginas arrives with embarrassment and the smell of burning. Like “WW” and its continued rebranding of what health looks like, seeing its flaws from this distance is shocking in its simplicity. We stand aghast beside a bonfire of vanities.

You see patterns form in how businesses like this scrabble in muck to stay relevant. Like the characters in Bushnell’s new book, WW is shrouding outdated body obsessions in modern, muddled ideas of wellness. But in daylight the money shows through, and their latest launch, Kurbo, a calorie-counting app for kids, is not just old-fashioned but distinctly icky.

Kurbo ranks food choices using a “traffic-light” system: green items can be eaten freely; yellow foods should be consumed in moderate portions; and red foods should make kids “stop and think”. The idea of my five-year-old “stopping” before accepting a KitKat, and “thinking” before quietly inputting it into an app, fills me with ancient dread. After “healthy eating week” at her school, I saw indignant confusion before a plate of biscuits. Food had become moralised – sweets tasted good, but were bad, and broccoli vice versa. Though the lessons were well-meaning, they proved confusing for shallow-fried brains, and she lectured me at length and wrongly about fat and sugar, talking over my quiet argument for a balanced plate. I was reminded, wearily, that eating is about so much more than food.

The idea of my five-year-old 'stopping' before accepting a KitKat fills me with ancient dread

In 2018, Weight Watchers announced it was taking the emphasis off before and after pictures, but on the Kurbo site, their “success stories” are cheerily illustrated with just that, including photos of Sophie, aged eight, drinking a milkshake, then… not (“I feel like I have more energy!”) – the small print below reads: “Results not typical”. For a weight-loss company struggling to place itself in a culture that’s turning away from diets, this is a clear attempt to soak up customers concerned about childhood obesity, with the app presumably marketed directly to their database of long-term dieters. But encouraging kids to focus on weight loss has been proven to trigger increased body dissatisfaction. Phones have a place in this – a 2019 study of 100 young people using nutrition apps found that almost half reported negative feelings, like guilt and obsession. WW’s app has launched in the US despite recommendations from the American Academy of Pediatrics, whose guidelines explicitly warn parents and healthcare providers about the risks of focusing on weight loss with children and adolescents, in part because dieting increases the risk of eating disorders exponentially. American teenagers who diet are up to 18 times more likely to develop an eating disorder, compared to those who don’t. And eating disorders in children are increasing: in 2018 the number of children and young people entering treatment for an eating disorder was 30% higher than two years earlier. But the thing that makes me roll my eyes (rather, perhaps, than stick them with a fork) is the fact that diets don’t work. The majority of dieters end up weighing more than they did before. The whole concept is a scam the size of the Fyre festival, an idea built on sand.

In order to sort out kids’ health, there are things we can do at home, like improve our own relationships with food and appearance, and there are things we can do in society, like contribute to political change that helps the most deprived families, those more affected by childhood obesity. This app is a throwback to those days when we bent to fit the lies we were told, rather than questioned their motives. And if we lived in a different kind of world, where bellies were not judged like garden vegetables, the value of a person based on more than appearance, perhaps a health app like this would work. But we live here, among the chips and pain, and in this world, a child should not be told to change their body.

Email Eva at e.wiseman@observer.co.uk or follow her on Twitter @EvaWiseman