Obese people can be considered as disabled, according to a top EU court.
However, it stopped short of saying that obesity was a condition that needed specific protection under European anti-discrimination laws.
The landmark decision will be closely read by European employers and means that companies might have to provide greater support to obese staff.
The case was instigated by a Danish court, which wanted guidance over a complaint of unfair dismissal brought by a child-minder who was sacked by a local authority.
Karsten Kaltoft, who never weighed less than 160kg (352 pounds) during his employment, argued that his obesity was one of the reasons he lost his job and that this amounted to unlawful discrimination - an allegation the council denied.
The Court of Justice of the European Union (EJC) ruled that EU employment law did not specifically prohibit discrimination on the grounds of obesity, and said the law should not be extended to make it a protected category.
However, the Luxembourg-based court said that if an employee's obesity hindered "full and effective participation of that person in professional life on an equal basis with other workers" then it could be considered a disability. This, in turn, is covered by anti-discrimination legislation.
Classifying obesity as a protected characteristic - such as sex, race or age - would have required employers to take measures to ensure obese workers could perform their duties on an equal footing with others.
"It would have opened a can of worms," said Crowley Woodford, employment partner at law firm Ashurst.
However, the nuanced ruling still leaves companies open to potential discrimination suits.
"If you consider the obese disabled, all of a sudden it triggers certain protections for employees," said Jacob Sand, a partner at Danish law firm Gorrissen Federspiel which represented Kaltoft.
Considering obesity a disability also reverses the burden of proof in workplace disputes over discrimination, Sand added, meaning it will be easier for employees to argue they had been discriminated against.
"That makes it a whole lot easier for employees in that it is easier to win the case," Sand said.
However, it does not mean that employers cannot fire someone whose size means that they are unable to do their job, rather that they must consider whether any adjustments need to be made to help the employee perform their role first, said Stefan Martin, employment partner at law firm Mayer Brown.
According to statistics from the World Health Organisation (WHO), based on 2008 estimates, roughly 23pc of European women and 20pc of European men were obese.
The issue of whether obesity is a disability has also been dealt with in US courts, where almost one in three adults is obese, according to WHO data.
The Danish court must now decide whether Kaltoft's obesity represented a disability.
It is expected to reach a decision before the end of next year.