Poll: Should obesity be considered a disability?
People who are obese could also be considered disabled, the European Court of Justice has ruled.
The judgment comes after the landmark case of a Danish childminder who was believed to be so fat he was unable to tie his own shoelaces, and was sacked by his employers four years ago.
The court, whose laws are binding throughout EU members states such as the UK, said obesity could be considered a disability if it "hinders the full and effective participation of the person concerned in professional life on an equal basis with other workers".
The ruling could force widespread changes across Europe in the way employers deal with obese staff and what support they might be legally required to offer.
According to the World Health Organisation, whose definition was relied upon in court, a person is obese if their body mass index (BMI) is over 30. It is calculated by taking a person's weight in kilograms and dividing it by the square of his or her height in metres.
The ruling has already raised serious concerns about the immediate and long-term impacts on employers in the UK, who may now need to take extra steps to cater to the needs of obese staff. This could include wider car parking spaces and changes to seats, desks and fire escapes.
National Obesity Forum spokesman Tam Fry said: "This has opened a can of worms for all employers in this country.
"They will be required to make adjustments to their furniture and doors and whatever is needed for very large people.
"I believe it will also cause friction in the workplace between obese people and other workers."
Mr Fry said he expected member states to apply to challenge the ruling.
He added: "This is the closest I've seen to the law being an ass."
The case was brought by Karsten Kaltoft, who had been a childminder for 15 years when he was made redundant by the Municipality of Billund local authority.
He is believed to have weighed more than 25st (159kg) at the time - the same as a fully grown American black bear. The council said it was making redundancies based on a decrease in the number of children who required the service, and did not disclose whether Mr Kaltoft's size played any part in its decision to let him go.
Reports suggested the childminder - who was obese throughout his employment - needed help tying his shoe laces and struggled with physical tasks.
He told the BBC earlier this year: "I can sit on the floor and play with them, I have no problems like that.
"I don't see myself as disabled. It's not OK just to fire a person because they're fat, if they're doing their job properly."
Claire Dawson, employment lawyer at Slater & Gordon, said the ruling "should encourage and support the full participation of obese people in the workplace".
She said: "Obesity in itself has not previously been classed as a disability in UK law.
"However, where an obese person has other health difficulties that can be associated with and potentially compounded by obesity, such as mobility difficulties, diabetes or depression, these may give rise to protection against disability discrimination at work.
"The European Court's decision does not change that position radically.
"Employers are required to make reasonable adjustments for disabled workers which, in the case of an obese worker, could include providing a larger chair or a parking space closer to the office, for example.
"We know that obese people are sometimes treated differently because of their weight, not only in the workplace. This decision upholds a principle at the heart of disability discrimination law which is that, where reasonably possible, barriers to employment which do not relate to a person's inherent ability to do their job should be removed."
One in four adults in the UK is obese, according to latest figures from the NHS.
Earlier this month researchers from McGill University in Montreal, Canada, said being obese can shorten life by eight years and condemn a person to almost two decades of ill-health.
Scientists used a computer model to predict that diabetes and heart disease were likely to deprive an obese person of up to 19 years of healthy living.