Britain is starting to ‘turn the tide’ on obesity with weight loss jabs set to put decades of growth into reverse, experts say.

A global analysis found the obesity crisis is slowing down or tapering off and could already be retreating in some countries.

Researchers led by a team at Imperial College London found the slowdown in high-income nations first occurred in school-aged children, followed by adults.

Their work, published in the journal Nature, looked at more than four decades of health data from 200 countries and territories, covering the period from 1980 to 2024.

When it comes to the UK, experts found the plateau for girls occurred around the year 2000, with the same happening in boys slightly later, but before 2005.

For women and men, obesity rates are still rising but are slowing down, they added.

The trend is thought to be due to people becoming more health conscious combined with a raft of public health measures aimed at reducing intake of sugary food and drink and boosting exercise.

Now leading health experts say obesity rates in the UK are likely to plummet within as little as a year once the NHS makes weight-loss jabs more widely available.

They highlighted trials showing obese people who use weight loss drug Mounjaro can shed 25kg (4stone) in a year, which would have a ‘huge impact’ on a national level.

An estimated 2.4 million people are taking weight-loss drugs in the UK but severe rationing by the NHS means the vast majority are currently forced to buy them privately.

NHS England plans to make them more widely available over the next few years, with health secretary Wes Streeting describing them as a ‘real game-changer’.

The shift in the UK’s weight trajectories happened at some point in the early-mid-2000s for women and shortly afterwards for men, lead researcher Professor Majid Ezzati said.

Since 1980, obesity rates in Britain have risen dramatically, increasing more than eight-fold among boys, from 1.5 per cent to 12.4 per cent, and more than six-fold among girls, from 1.6 per cent to 10.1 per cent.

Among men, rates have climbed from 5.7 per cent to 26.7 per cent, while among women they have risen from 8.5 per cent to 29.6 per cent.

However, the pace of growth appears to have slowed in the past decade, with rates rising by around four percentage points in men and boys, and roughly two to four points in women and girls since 2014.

Professor Ezzati said the UK remains mostly in the top ten countries among high-income western nations for obesity rates but the trajectory ‘has been completely flattened’.

While the impact of weight loss injections such as Wegovy and Mounjaro are not yet reflected in the data, experts believe they could play an important role in future trends.

Professor Ezzati said the focus should be on making these drugs more affordable to all who need them around the world.

He told a briefing: ‘They have been a game-changer at a clinical level, for individual patients, and we are learning more and more about them in trials.’

Professor Ezzati said the drugs represented ‘another tool to be used that will have large benefits for individuals and perhaps at the population level’.

The current study did not reflect their use, owing to the time period studied, ‘but going forward, they could be a game-changer’, he added.

Dr Louis Aronne, of Weill Cornell Medicine, in New York, who this week presented a separate study at the European Congress on Obesity, said weight loss drugs will have a bigger impact on public health than statins and they are already ‘turning the tide’ in countries where they are widely available.

He added: ‘I absolutely expect to see the same in the UK as these treatments get adopted by the National Health Service and become more widely available.

‘These will save the National Health Service in the long run and it will benefit many aspects of health.

‘It just depends when the National Health Service adopts it widely - that is what it will take.

‘As soon as that happens, within a year, we should see a huge impact on obesity.’

Professor Jason Halford, a former president of the European Association for the Study of Obesity, said weight loss jabs should ‘accelerate’ progress towards reducing obesity rates, if people can access treatment.

The new study found that obesity prevalence continues to rise in many low and middle‑income countries, particularly in Africa, Asia, Latin America, and Pacific and Caribbean islands.

In all, the team analysed weight and height measurements from more than 232 million people aged five and over (70 million people aged five to 19, and 162 million aged 20 or older).

More than 1,900 researchers contributed to the study.

Dr Marie Spreckley, research programme manager at the University of Cambridge, said: ‘For the UK, the findings suggest that obesity prevalence may be stabilising, but at a relatively high level compared with many other high-income countries.

‘This should not be interpreted as evidence that the problem has been solved.

‘A plateau at high prevalence still represents a substantial burden for individuals, healthcare systems and society, and reinforces the continued need for effective prevention, treatment and long-term support strategies.’