Hello! I believe you are asking about Anita Desai's short story "A Devoted Son."
In this story, Varma is justifiably proud of his son, Rakesh, who earns his MD and then goes to America to practice medicine in a prestigious hospital. Rakesh is so filial that he bows and touches his father's feet when he returns to his father's house. Rakesh marries an uneducated girl of his mother's choosing: a plump, old-fashioned and placid daughter of his mother's childhood friend, who soon bears him a son.
Rakesh eventually starts his own clinic after rising up the ranks to the position of director at the city hospital. Varma, now content with his life, soon retires. However, his life quickly falls apart. He
developed so many complaints and fell ill so frequently and with such mysterious diseases that even his son could no longer make out when it was something of significance and when it was merely a peevish whim.
Varma takes to the habit of stretching out on the bed and then lying still. This invariably puts the whole household into a frenzy of anxiety. Then, just as suddenly, Varma would sit up ramrod straight, "spitting out a big gob of betel-juice as if to mock their behavior." Now, why does Varma mock the behavior of his family? As time passes, we see that Rakesh's filial devotion borders on an almost obsessive preoccupation with prolonging his father's life without the benefit of adding any meaningful joy to his father's existence. Rakesh measures out what his father is to eat; he deprives Varma of fried foods, rich fare and all the delicacies Varma has loved all his life. Varma's status of powerful patriarch has now been fully supplanted by the tyranny of modern medical science which sees death as a tragedy.
If I ask him for one more piece of bread, he says no, papa, I weighed out the ata myself and I can’t allow you to have more than two hundred grams of cereal a day.
Varma's childish act of spitting beetle juice on anyone near him is an impotent rebellion against the hypocrisy of his family: on the one hand, they hail him as the patriarch, but on the other hand, they ration out his pitiful fare as if he is lower than a servant. Varma is tired of the powders and pills he is forced to ingest; he is tired of all the boiled foods he must eat.
[I]s it possible, even in this evil age, for a son to refuse his father food?...on such a miserable diet, Varma found himself slipping, weakening and soon becoming a genuinely sick man.
He is forced to bribe his grandchildren for treats; after all, the Hindu concept of transactional food exchange has been denied him. The essence of food (anna) is derived from the giving of food (annadana). Rakesh's rigid modern medicine has deprived his father of one of the joys of life: eating what one enjoys and likes. This is partly how life is enriched, and perhaps even prolonged, in traditional Hindu culture; food is not only nourishing, it is therapeutic. Rakesh's disregard of this important aspect of his father's beliefs prompts Varma's mockery.
Thanks for the question!