jabs such as Wegovy are "lifelong treatments" and most people who stop taking them will lose the effects, a scientist who developed the revolutionary drugs has said.

Professor Lotte Bjerre Knudsen, chief scientific advisor to Danish pharmaceutical company Novo Nordisk, challenged the idea that their popularity would lead to over-medicalisation of .

The spending watchdog has said patients should only be prescribed Wegovy - licensed for weight loss and treating - for up to two years.

But Prof Knudsen said: "These kinds of medicines are approved for lifelong treatment, that's the way it is. The longest trial that we have is around five years.

"You should expect that for most people, if they stop taking the medicine they will also lose the effect. That's no different than medicines for diabetes, for cardiovascular disease."

The drugs, known as receptor agonists, work by mimicking the action of hormones that make you feel full.

They have been hailed as transformative in the battle against obesity, with studies showing they can help patients lose up to a quarter of their body weight.

Professor Knudsen, who was speaking on Radio 4's Today programme, played a key role in the development of liraglutide and semaglutide, two active ingredients in many of the jabs.

Using the example of patients with high blood pressure, she added: "You don't tell people to stop taking their anti-hypertensives just because their blood pressure is under control. This is exactly the same.

"With other preventative systems like much more exercise or a real change in what you eat, maybe there are some people who can [stop the treatment]. But there will also be people who cannot."

The Danish scientist said the global obesity crisis had only worsened in the three decades she has been working in this field. Meanwhile, societal changes or programmes to help people exercise more and eat more healthily have had little effect, she said.

She added: "Obesity is very complex. For some, there are genetic factors underlying why you have obesity.

"For some, there are hormonal factors, psychiatric factors. It's just a really complex environment combined with the fact that maybe our food environment isn't the healthiest compared to what it was if we go back 100 years where mostly only natural ingredients were available.

"So no, I wouldn't say we're giving up but it's getting harder for people with the society that we live in today."

Her comments come after the expert who leads the UK government's Obesity Healthcare Goals programme warned that giving the drugs to everyone who is eligible in the UK "would simply bankrupt the NHS".

Prof Naveed Sattar, an expert in cardio metabolic medicine at Glasgow University, told the BBC: "The cost of the drugs is still at a level where we cannot afford to treat several million people within the UK with these drugs."

Asked whether she was concerned about the over-medicalisation of obesity, Prof Knudsen said: "I really wouldn't want to push that kind of blame on people to say that it's morally wrong.

"It's actually unhealthy to be too obese. I keep thinking about the 30 years I've spent on this and how many times people have asked for these types of medicines to be available."