“Fifty percent of my questions are about why their hair is not falling out,” Dr. Watsa said. “It is the zillionth time I have answered it.”

The son of a military doctor, Dr. Watsa trained as an obstetrician and gynecologist and joined the ranks of the progressive activists at the Family Planning Association of India, which promotes sex education and the use of contraception. But even in that liberal-minded group, his focus on the quality of sexual life made him an outlier.

Amita Dhanu, a longtime colleague at the association, recalled the furor that resulted when Dr. Watsa introduced human sexuality to the association’s training sessions, illustrating his workshop with slides of erotic carvings from medieval Hindu temples. The response of the other activists, she said, was to say, “This is basically pornography.”

IT was, in a way, logical that Dr. Watsa would surface in a more populist venue. For decades, as conservative groups battled against the introduction of sex education curriculum in Indian schools, advice columnists have found themselves barraged by basic questions, often in huge quantities. When the women’s magazine Femina introduced a sex column, an outraged reader filed an obscenity complaint with the police, claiming that the magazine’s editors were fabricating outrageous letters to increase readership. Sathya Saran, then the editor, responded by delivering a sack of unopened letters to the judge.

“He read them over the lunch hour and dismissed the case,” she said.

Dr. Watsa said yes when Meenal Baghel, the editor of The Mumbai Mirror, approached with the idea for Ask the Sexpert. It was the first time such questions appeared in a daily newspaper in India, rather than the specialized venue of a men’s or women’s magazine, and it remains — even nine years later — a daily shock to Indian sensibilities.

Commuters in Mumbai can be spotted folding over their newspaper before reading it on the train, and subscribers have been known to snip the column out with scissors before sharing the newspaper with their children. One Mumbai journalist said she liked to read the column aloud to her mother as a form of torture, routinely forcing her to run from the room. As for Dr. Watsa, he will take his position in his study in the morning, working his way through another batch of letters. His wife, Promila, died in 2006 after a 52-year marriage, leaving him to look after the orchid she had nursed on the balcony. It was a happy marriage, Dr. Watsa said — “I hope she thought so, too” — but he was diffident when asked about their sex life. “Sometimes you felt in marriage that you’re not performing as well as you should,” he said. “I think the wife handled it better than I did.”