The EU's top court is considering a test case which could oblige employers to treat obesity as a disability.
Denmark has asked the European Court of Justice to rule on the case of a male childminder who says he was sacked for being too fat.
Karsten Kaltoft weighs about 160kg (25 stone; 350 pounds). He told the BBC that "bad habits" had made him fat but that his size was "no problem" at work.
The court's final ruling will be binding across the EU.
It is seen as especially significant because of rising obesity levels in Europe and elsewhere, including the US. A survey in England in 2012 found that more than half of adults were obese or overweight.
The Danish courts asked the ECJ judges in Luxembourg to clarify European law in Mr Kaltoft's case.
'Doing job properly'
In an interview with the BBC World Service, Mr Kaltoft denied reports that he was unable to bend low enough to tie children's shoelaces.
Describing his work with children, he said: "I can sit on the floor and play with them, I have no problems like that."
"I don't see myself as disabled," he said. "We hope the outcome is that it's not OK just to fire a person because they're fat, if they're doing their job properly."
When asked if his employer, Billund local authority, had done anything to help him, he said they had paid for him to go to a gym for three months.
"I tried regular exercise. Of course I don't run a marathon, but weight training: I did that, it was OK," he said.
He worked for Billund authority for 15 years and was dismissed, the authority said, because there was a decline in the number of children. No further explanation was given as to why he was selected for dismissal.
Audrey Williams, an employment discrimination expert at Eversheds law firm, said the judges would have to decide "whether obesity itself should trigger preferential rights, or should only impact where an individual, due to obesity, has other recognised medical issues".
If the judges decide it is a disability then employers could face new obligations, she told the BBC.
Employers might in future have a duty to create reserved car parking spaces for obese staff, or adjust the office furniture for them, she said.
The judges will have to decide whether obesity is covered under the EU's Employment Equality Directive, which outlaws job discrimination on grounds of disability.