Seriously-ill Leslie Burke wants a dignified death without the pain of being starved, his lawyers have told the Court of Appeal.
Leslie Burke won the original case
The 45-year-old, who has a degenerative brain condition, won a landmark ruling last year to stop doctors withdrawing food and drink when he cannot speak.
But the General Medical Council has appealed, saying it would put doctors in an impossible position.
Richard Gordon QC, for Mr Burke, said the issue was about "who decides".
In the original case, Mr Burke argued the GMC advice, which gives doctors in cases such as Mr Burke's the ultimate say on what treatment to give a patient in the final stages, was an infringement of his human rights.
Mr Justice Munby sided with Mr Burke and said that if a patient is competent - or, if incompetent, has made an advance request for treatment - doctors have a duty to provide artificial nutrition or hydration.
Mr Gordon said Mr Burke, who has cerebellar ataxia - an umbrella term for nervous system disorders that cause lack of co-ordination, but does not affect mental faculties - was a legally competent person and wanted to receive food and water administered by artificial means when he had difficulty in eating or drinking.
"If he doesn't get it, he fears he will suffer and he will die of thirst and malnutrition.
"He does not want to be told by a doctor that it is in his best interests not to be given food and water by artificial means.
"He doesn't want to suffer pain or death by being starved or dehydrated.
"He doesn't want an undignified death and, in particular, he doesn't want doctors to tell him it is too burdensome for him to live because he will suffer too much.
"He wants to be the arbiter of how much he is prepared to suffer."
Earlier, Philip Sales, for the government, said if the original ruling was upheld, patients would be allowed to demand other treatments, which would have "very serious implications" for the NHS.
Artificial nutrition is classed as a form of treatment by the GMC and, therefore, last July's ruling, which was hailed as a breakthrough for the rights of terminally-ill patients, raised questions about medical interventions.
Mr Sales said: "A general right, as identified by the judge in the High Court, for an individual patient to require life-prolonging medical treatment has very serious implications for the functioning of the NHS.
"It may be interpreted as giving patients the right to demand certain treatments, contrary to the considered judgment of their medical team, that would lead to patients obtaining access to treatment that is not appropriate for them, and to inefficient use of resources within the NHS."
The case continues.