Q & A

Every weekday morning, he meditates for an hour, takes an ice-cold bath to give him "mental confidence", and has a breakfast of "salt juice": water mixed with Himalayan salt and lemon. Unless he is working from home, he walks five miles to work. If he's at home, he uses a standing desk and an infrared lightbulb.

He does not eat until the evening. It will be "a meal of fish, chicken, or steak with a salad, spinach, asparagus or Brussels sprouts", explains an article on his wellness habits by CNBC. "He has mixed berries or some dark chocolate for dessert."

At weekends, he does not eat at all between Friday and Sunday night. "The first time I did it, like day three, I felt like I was hallucinating," he told a fitness podcast last month. When he tried again, he noticed that "time really slowed down". At night time, he tracks his sleep using an Oura ringA 0 plus ring which also tracks daily activities..

For some, he is seen as a guru. Last weekend, The New York Times published a profile calling him the "Gwyneth PaltrowAn American actress and businesswoman, known today for her lifestyle brand. for Silicon ValleyA global centre of technological innovation in Northern California. It is home to many start-up and global technology companies including Apple, Facebook and Google. ". According to journalist Nellie Bowles, "An endorsement from Mr. Dorsey can put products out of stock for weeks."

But others are worried about the message his habits are sending. National Eating Disorders Association CEO Claire Mysko told Mother Jones that his endorsement of fasting is "potentially dangerous", particularly to those who are vulnerable to eating disorders.

The science about the benefits of fasting is confused. One 2017 study found "no significant advantage" over simply eating healthy, regular meals, when it comes to losing weight.

Meanwhile, the neuroscientist Mark Mattson has suggested that some forms of controlled fasting may help stave off brain diseases like Alzheimer's and Parkinson's. Most scientists conclude that more research is needed.

All of this matters. Dorsey is not just any tech CEO. Twitter is a hugely influential website, with a lot of problems - from online abuse to the disruption of democracy.

So what should we think of him?

You don't have to follow his advice (and you should definitely not go for days without food), but he is clearly committed to hard work, say some. These elaborate wellness routines may look strange, but they come from a place of wanting to be healthier and more productive. Better that than the reckless behaviour of Dorsey's opposite, Elon MuskA South African-born entrepreneur whose companies have included the online payment service PayPal. He now controls Twitter, renamed 'X'..

He is a worrying figure, argue others. His routines are not inspiring, they are obsessive and unhealthy - and they set a terrible example for those who admire him. Dorsey acts more like a cult leader than a man in charge of a website that is changing the very fabric of society.

What do we know? Jack Dorsey is the founder and CEO of Twitter and a payments tech company called Square. His estimated wealth is $5 billion. He often tweets about his diet, meditation and other health routines. He also explained them in more detail to the Ben Greenfield Fitness: Diet, Fat Loss and Performance podcast last month. He says he is shifting his focus on Twitter from growth to "conversation health".

What do we not know? Whether he is up to the job. He has been criticised for his lack of urgency when it comes to Twitter's problems - concerns which are only exacerbated by his outwardly calm manner. We also do not know whether he really has an eating disorder, as this would be impossible to diagnose based on Tweets and descriptions alone.