But public memory has nano-second retentiveness, so we forget that Mr Modi's excessively low-profile predecessor Manmohan Singh is also vegetarian, teetotal and routinely put in 12- to 15-hour days right to the end of his discredited government's second term.
This general approbation of workaholism in our top political leaders has, over the last few decades, become something of an approved public image. Maybe it allows us to feel reassured that our elected head of government is fully engaged with the myriad problems that plague a country as diverse and poor as India. This is probably why H D Deve Gowda, a uniquely hapless occupant of No 7 Race Course Road in the late nineties, felt it incumbent to insist to a magazine that he worked very long hours - though bureaucrats of the time recall him occasionally making up for lost sleep in meetings and Parliament with equal conscientiousness.
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Still, you can't help wondering, what do these guys do for relaxation? Beyond the insider gossip circles, those aspects of our prime ministers are rarely publicised. We know, for instance, that Dr Singh had an unexpectedly dry sense of humour but may have had a hazy concept of the term "fun".
Sanjaya Baru, his former media advisor, once told a TV channel a charming story of how an official visit to Goa ended early, leaving them with time to spare before the official flight out. Dr Singh was dismayed, Mr Baru recalled, because he didn't know what to do with that extra time at one of the world's most visited leisure destinations.
If we exclude Jawaharlal Nehru, Rajiv Gandhi and Atal Bihari Vajpayee, none of whom saw reason to mask the relatively hedonistic aspects of their personalities, the public image of our prime ministers appear to be unrelentingly, and alarmingly, work-focused.
Contrast this with leaders in the developed democracies. The President of the United States, unarguably the most powerful person in the world with responsibilities at least as onerous as India's prime minister, openly takes vacations and has other interests. Indeed, George W Bush took holidays on his Texan ranch so regularly that he attracted acid comment from the East Coast press.
Barack Obama and his photogenic family make annual pilgrimages to his birth state of Hawaii. He plays golf as often as he can (famously approving the Navy Seal operation to capture Osama Bin Laden before heading off to the links), basketball occasionally and is a copious reader. He takes beer bets with other leaders on the outcome of hockey matches. He and his wife dine at a favourite restaurant on their wedding anniversary. He patently enjoys himself without any noticeable diminution of his efficacy even though he took office when the US was going through one of the worst periods.
Bill Clinton, another successful President, read widely, too, through his two terms as President, was a talented saxophone player (and even, like John F Kennedy, found the time to indulge in other extra-curricular interests, though those nearly cost him his presidency).
Or consider Angela Merkel, who heads Europe's most powerful country and has proved a durable leader. At the heart of the Euro crisis, she took time out to watch the German football team play. At the gathering of the G8 summit in Camp David in 2012, leaders gathered to watch the Champion's League Final between German club Bayern Munich and English club Chelsea. Ms Merkel and then British Prime Minister David Cameron sat side by side and animatedly followed the fortunes of that match. Ms Merkel also skis, recently fracturing her pelvis during a skiing holiday in Switzerland.
Russia's authoritarian President Vladimir Putin has a personal website with an entire section devoted to his interests. Some are well known, like martial arts, ice hockey and skiing, fishing, horse-riding and whitewater rafting. He also apparently "enjoys watching animals in their natural habitat" and has taken the Amur tiger, white whale, polar bear and snow leopard under his personal patronage.
Now, Mr Putin is the kind of "strong" leader for which some Indians yearn. Yet he has found it necessary to highlight a kinder, gentler side to his image. Perhaps it would do our leaders a world of good to demonstrate that governing India need not skew what the corporate world calls work-life balance. After all, workaholism isn't necessarily a guarantor of India's gross national happiness.