It has long been celebrated as the most attractive male physique – but the popularity of the 'dad bod' could be waning, according to a new study.

For years the softer, more relaxed outline synonymous with Vince Vaughn, Seth Rogan and David Harbour has been depicted as the ideal body shape.

However, research now suggests women prefer a leaner, more athletic build like that sported by Brad Pitt and Ryan Reynolds.

Men, meanwhile, still seem to favour women who are a bit curvier, such as Kelly Brook, Beyoncé and Nigella Lawson.

The results suggest that when it comes to attraction, people are more likely to be drawn to the middle ground rather than extremes that are promoted by social media.

And it reveals that ultra–slim or hugely muscular bodies are still being out–competed by more natural shapes.

'The most interesting thing about this analysis is that people were not choosing the most extreme body types that we are normally led to believe is the ideal,' a spokeswoman from SoloFun, which commissioned the study, said.

'People attracted to men, for example, preferred a lean body type, whereas people attracted to women leaned more towards a softer, curvier body type.'

As part of a poll, more than 2,000 adults were shown body fat comparison images and were asked to choose the one they found most attractive.

Analysis revealed that the most attractive male body fat percentage was not the ultra–lean, superhero–style physique often promoted online.

Instead a lean, athletic range of around 15 per cent body fat was preferred.

According to the research, people attracted to men were most likely to favour a body that looked healthy, fit and naturally athletic, suggesting the once–popular 'dad bod' may be falling out of favour.

A 20 per cent body fat level came in second place, followed by 25 per cent. The least popular choice was the highest body fat range of 35 per cent.

Meanwhile, for participants who were attracted to women, the most preferred body fat range was 30 per cent.

This suggests they favoured a softer, curvier body type rather than a lean physique.

A 25 per cent body fat level came in second place, while 45 per cent body fat – the highest available – was the least popular option.

While the numbers look different in men and women, this is down to the way that men and women use and store fat in their bodies.

A 15 per cent body fat level on a man does not visually compare with 15 per cent body fat on a woman, as women naturally carry higher levels of essential body fat.

While healthy body fat for men is often roughly 10–20 per cent, for women it is usually 20–30 per cent.

A woman at 15 per cent body fat would usually look extremely lean and may experience hormonal issues, while a man at 15 per cent often looks athletic and healthy.

Meanwhile a woman at 30 per cent body fat can still appear curvy and healthy, while a man at 30 per cent would usually appear much heavier.

There are many theories about why women prefer different physiques but it is thought that females associate big muscles with strength, health and protection.

A Yale professor has previously claimed some women choose men with dad bods because the physique indicates the man will live longer.

Richard Bribiescas, a professor of anthropology, said this makes them better at passing on their genes to offspring and fighting off illnesses, which could make them appear more attractive to women.

Separate research has previously revealed that women prefer men with muscular shoulders and torsos – but only if they're tall.

According to experts, a higher 'shoulder–to–hip ratio' (SHR) – where there's a bigger circumference around the shoulders than there is around the waist – is a mark of attractiveness.

However, men who aren't very tall may not be able to change a woman's perception of how attractive they are – even with a lot of built–up muscle, the study suggests.

'Our results showed that women's perceptions of males attractiveness, masculinity, and fighting ability were influenced by, and interacted with, height and SHR,' lead author Farid Pazhoohi told PsyPost.