From Dachshunds' long bodies to Pugs' squashed faces, many of the most popular dog breeds are known for their extreme bodies.

While these exaggerated characteristics are often perceived as 'cute', they can leave dogs with severe health issues, and as a result, a poor quality of life.

Now, vets have issued new guidance on the 10 extreme body conformations that owners should aim to avoid.

This includes a bulging or domed skull, twisted legs, a sloped back, and protruding eyes.

'No owner ever wants an unhealthy dog but the huge popularity of dogs with extreme conformations suggests that many owners have not fully grasped the link between body shape and quality of life for dogs,' said Dr Dan O'Neill, Associate Professor for Companion Animal Epidemiology at the Royal Veterinary College (RVC).

Vets have issued new guidance on the 10 extreme body conformations that owners should aim to avoid

Short and twisted legs - as seen in Dachshunds - can lead to back problems, the researchers warn

The 10 extreme body conformations owners should avoid

1. Flat-faces
2. Large and protruding eyes
3. Short, twisted legs
4. Facial or body skin folds
5. Tailessness at birth
6. Clearly overshot or undershot jaw 
7. Disproportionately broad head and shoulders
8. Eyelids turned in or out 
9. Bulging or domed skull
10. Sloped back with excessively low rear and excessively flexed hind legs

Several popular dog breeds suffer from 'extreme conformation', which is where an exaggerated body shape negatively affects their health and welfare. 

Most of these extreme features did not evolve naturally, and instead are the result of hundreds of years of breeding. 

Now, the International Collaborative on Extreme Conformations in Dogs (ICECDogs) has worked with the RVC to publish new guidance to help prospective owners choose dogs with 'good innate health'.

'Innate health is a concept that has been developed following a decade of research at the RVC and refers to a dog's capacity to enjoy life without limitations from health issues linked to extreme conformations,' the RVC explained in a statement. 

In order to have good innate health, the researchers say that a dog must be able to breathe freely at rest and during exercise, without the need for corrective surgery. 

They must also be able to maintain a normal body temperature, move freely, eat and drink effectively, hear, smell, see, self-groom, and sleep effectively. 

What's more, healthy dogs should be able to reproduce, and communicate with other dogs, according to the researchers. 

Somewhat unsurprisingly, a flat face tops the list as the number one extreme body conformation to avoid. Flat-faced breeds include pugs (pictured), English Bulldogs, and French Bulldogs

Tailessness - as seen in the Boston Terrier - at birth can make it difficult for dogs to communicate with one another

Is your dog healthy? 

To be classed as healthy, your dog should be able to: 

• Breathe freely at rest and during exercise, without the need for surgery
• Maintain body temperature
• Move freely
• Eat and drink effectively
• Hear, smell, see, self-groom, eliminate and sleep effectively
• Reproduce
• Communicate with other dogs

Based on these criteria, the researchers have come up with a list of 10 extreme body conformations to avoid in dogs. 

Somewhat unsurprisingly, a flat face tops the list as the number one extreme body conformation to avoid. 

Flat-faced breeds include pugs, English Bulldogs, and French Bulldogs. 

'Flat-faces (brachycephaly) commonly lead to health issues including difficulty breathing and eye ulcers,' the RVC explained. 

Large and protruding eyes, such as those seen in the Pekingese, should be avoided as they increase the risk of eye damage and infection. 

Meanwhile, short and twisted legs - as seen in Dachshunds - can lead to back problems. 

'Affected dogs with excessively short legs and a disproportionately long body frequently suffer spinal and neurological problems,' the RVC said. 

Facial and body skin folds on breeds including the English bulldog should be avoided as these can lead to skin infections and pain. 

Breeds like the Bloodhound, with eyelids turned-in or turned-out can experience painful eye problems

Breeds with a clearly overshot or undershot jaw such as the Boxer can experience difficulty eating

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And tailessness - as seen in the Boston Terrier - at birth can make it difficult for dogs to communicate with one another. 

Breeds with a clearly overshot or undershot jaw such as the Boxer can experience difficulty eating, while a disproportionately broad head and shoulders, as seen in the French bulldog, often results in the inability to deliver puppies. 

Meanwhile, breeds like the Bloodhound, with eyelids turned-in or turned-out can experience painful eye problems, while breeds with a bulging or domed skull, like the Chihuahua, are at higher risk of brain diseases. 

Finally, owners should avoid dogs with sloped backs, low rear ends and flexed hind legs, such as the German Shepherd Dog, as these traits are commonly associated with locomotion problems. 

Dr O'Neill told MailOnline that some of the most commonly affected breeds include Basset Hounds, Boston Terriers, Dachshunds, English Bulldogs, French Bulldogs, Germany Shepherd Dogs, Neapolitan Mastiffs, Pekingese, Pugs, Shar Peis, and Welsh Corgis. 

Based on the findings, the researchers are calling on Britons to avoid promoting, breeding, selling, or acquiring dogs with these 10 extreme conformations. 

Dr Michelle Groleau, ICECDogs member, added: 'There is an urgent need for the public to be made aware of the severity of the current situation and to learn how they can contribute to a solution'.