Telling children they are overweight actually leads to them growing up carrying more weight, MPs have heard.
Experts said there is zero evidence that weight loss diets work in the long term and they lead to children piling the pounds back on eventually.
Psychologists told the Health Select Committee that stress and stigma have negative health impacts that increase the risk of weight gain over a lifetime.
Experts said the National Child Measurement Programme - which takes the weight and height of all children in reception class and Year 6 - is contributing to Britain’s obesity epidemic.
MPs were told that the goal of losing weight should be replaced with a focus on children’s self esteem and encouraging healthy lifestyle habits, such as cooking from scratch and exercise.
Dr Angela Meadows, of University of Essex, said: “The long term effects of weight loss tends to be weight gain.
“Telling children that they’re overweight, it has been tried. It tends to have the opposite effect to that intended. “It is associated with higher weight further down the line.
“It tends to promote a body of issues such as mental health problems, anxiety, depression, isolation, internalised weight stigma and maladaptive coping behaviours.”
The hearing came days after it emerged Boris Johnson is scrapping curbs on junk food advertising and unhealthy BOGOF deals.
Britain’s obesity epidemic means four in ten children are now overweight or obese by the time they leave primary school. And the proportion of five year olds who are obese has shot up by 45% in a year.
Dr Meadows, a lecturer in psychology, added: “Diet interventions in studies and randomised controlled trials have horrifically bad results and they are not associated with improvements in metabolic function, except where there is an exercise intervention. Exercise is good for just about every system in your body.
“Everything that we’re trying to do to reduce their weight is not evidence based.
“We cannot ethically promote intentional weight loss intervention as a health giving behaviour, because it isn’t. And although this might sound quite radical, the best thing to do would be to stop interfering."
She added: “Over the last 30 years, there has been no progress whatsoever on changing the trajectory of obesity.
“This is despite hundreds of millions of pounds being spent on intervention services and the National Child Measurement Programme.
“None of it is working and there’s a reason for that. Weight is not as much under individual control as we like to think it is.
“Things that we do to control weight, such as food restriction dieting, they tend to have rebound effects where you end up heavier than you were when you started.
“Stigma itself is a chronic stresser and this is true for weight stigma.
“The body responds to stress in very well known ways, by increasing stress hormones such as cortisol. All of which is associated with increased risk of diabetes, heart disease, hypertension and some cancers.”
Helen James, Founder, Nutriri, a social enterprise advocating a weight-neutral approach, said: “I’ve spoken to social prescribers who dread making the calls to parents whose children have been picked up through the National Measurement Programme.
“It feels very inflammatory, the telephone call in the first place.”
The Government will now delay a ban on promotions of foods high in fat, salt and sugar following pressure from Tory backbenchers, citing the cost of living crisis as a reason.
This is despite its own impact assessment saying banning BOGOF deals on junk food would reduce unnecessary household spending.
A ban on TV junk food adverts before a 9pm watershed has also been put on hold for a year following pressure from manufacturers.
Campaigners now fear the policies may never happen if a General Election is on the horizon.
Tam Fry, chair of the National Obesity Forum, defended the UK’s weight measurement programme and called for it to be expanded to identify overweight toddlers.
He told MPs: “By several decades I am the oldest person in this room, and I remember being weighed and measured every year way before there was any debate about whether it was a good idea or not. It was just like brushing your teeth.
“The nit nurse would come in, stick you against a wall and write some figures down. We didn’t care because we were not overtly made aware if there was a problem.
“You see whether their weight is going up, keeping on the right centile, or going down. And then you give them advice.
“We have now to look at the data. And without the data you cannot make any sensible decisions.”
