The obsession with fasting overlaps with a trend for what is often termed ‘biohacking’ – the idea that your body is a system that can be quantified and optimized

Eating is so last season; these days all the cool kids fast. Fasting diets have rocketed in popularity over the last few years, garnering a number of high-profile fans. Like Twitter CEO Jack Dorsey, for example, who tweeted last month that he had “been playing with fasting for some time”. Dorsey explained that he does “a 22 hour fast daily (dinner only), and recently did a 3 day water fast”. The billionaire added that the biggest thing he had noticed after depriving himself of food was “how much time slows down. The day feels so much longer when not broken up by breakfast/lunch/dinner. Any one [sic] else have this experience?”

I have! I’ve had lots of experience with the various side effects of fasting because I did it a ton as a teenager: it was called “anorexia”. And it wasn’t fun. It wrecked my health and took me years to recover.

Any eating behaviors that involve restriction or rigid rules is concerning Dr Allison Chase

Fasting, of course, is not synonymous with anorexia. Nor is it necessarily problematic. However, as Dr Allison Chase, an eating disorder specialist, tells me over email, “any eating behaviors that involve restriction or rigid rules is concerning” and can be a precursor to diagnosable eating disorders.

Also concerning is the way these behaviors are glamorized, particularly in Silicon Valley, where a number of high-profile tech execs extol the transformative power of extreme fasting. Meanwhile the compulsive measuring behaviors associated with eating disorders, including obsessively tracking your calorie intake and exercise, have been normalized by fitness tracking apps and the Silicon Valley ethos that constant self-examination leads to self-improvement.

Starving yourself and constructing rigid rules and rituals around when and how you eat is generally seen as a problem when it’s teenage girls doing it; when tech bros do it, it’s treated very differently. Indeed, in many ways it feels like Silicon Valley is inadvertently rebranding eating disorders.

Do you even fast, bro?

It’s worth slowing down and defining “fasting”. As Dr Valter Longo, who is director of the Longevity Institute at the University of Southern California, and something of a rock star among the fasting community, explains to me over the phone, the word “fasting” doesn’t mean much. It’s about as instructive as talking about “eating”, he says.

Longo notes that there are four distinct approaches to fasting, “which all have benefits and limitations”. The first is alternate-day fasting. The second method is often known as the 5:2 diet and involves eating normally five days a week followed by two days where you only eat around 500 calories. Then there is time-restricted feeding, where you fast 12-18 hours a day and consume all your calories within a narrow eating window. Finally there is the Fasting Mimicking Diet™, which is Longo’s brainchild. This involves eating a low-calorie diet that follows a very specific carbohydrate/protein/carbs ration for five days a month, a few times a year. The specially formulated diet costs $225 a pop and, according to the website, “provides scientifically researched micro- and macro-nutrients in precise quantities and combinations that nourish you, but are not recognized as food by your body and therefore mimics a fasting state!”

Fasting 12-13 hours a day is safe but things get more complicated when you fast 16-18 hours Dr Valter Longo

Longo believes that fasting, in general, can be highly beneficial. He likens it to a “reset” mode on your body that helps eliminate damaged cells and replace them with newly regenerated ones. Various studies, he notes, have shown that “fasting is as good as chemotherapy” in treating cancer and there is growing evidence that fasting can help with longevity by lowering markers of aging such as cholesterol and blood pressure. (While a few studies on mice suggest fasting may improve the efficacy of chemotherapy there remains a lot more research to be done and fasting should not be considered an alternative to chemotherapy.)

However, while there is exciting research about the efficacy of fasting, there are also some studies that show it can have negative effects. Longo stresses that it’s always important to put safety first and warns against being too extreme. For example, he says: “There is very little doubt that fasting 12-13 hours a day is safe but things get a little more complicated when you fast 16-18 hours.” Clinical studies have shown this sort of extended fasting can have positive effects on metabolism but also a number of negative results, such as an increase in gallstones.

Longo unambiguously advises against the sort of extreme three-day water-only fasts that Dorsey said he was playing with, and that seem particularly popular in Silicon Valley. “We’re no longer cavemen we’re not equipped to be doing extreme water-only fasting diets,” Longo stresses. “Your blood pressure can go very low. It’s very dangerous stuff.”

Hacking your body

Silicon Valley’s obsession with extreme fasting overlaps with a trend for what is often termed “biohacking”; the idea that your body is a system that can be quantified and optimized.

Geoffrey Woo, the 30-year-old CEO of Hvmn, a “human enhancement” company, is an enthusiastic proponent of biohacking and grew interested in fasting as a form of self-improvement. “The way I think about consumption, you’re taking inputs into your digestive system for survival and optimizing for performance outcomes,” he explains to me. “Fasting is a deliberate thoughtful pause in consuming anything except water. A lack of input is still a signal.”

Woo and his colleagues started off by doing 60-hour fasts and measuring the effects of these on their body in minute detail. “When I do aggressive experiments I have an implant that tracks glucose continuously for a couple weeks,” Woo says, and “I may do quarterly blood panels for things like lipids and C-reactive proteins”.

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Having experimented with fasting for a while, Woo now has a regular routine: he does an 18-hour fast daily, and does a 24- or 36-hour fast one to two days a week. “I know it can come across robotic and complicated,” he acknowledges, “but eating three meals a day could also come across as complicated if you’re not used to it.” Woo also acknowledges that there may be a risk with fasting going too far but says “there’s a risk element with any behavior”. There’s even a risk element with the current western diet, he says, which he thinks “should be considered disordered eating”. He notes that one-third of Americans are diabetic or pre-diabetic and there are soaring obesity rates. “That’s the most compelling data on what’s disordered or not.”

Justin Rezvani, a 30-year-old tech entrepreneur based in LA has similar views. He started getting into fasting a year ago; he had just sold his social media business for a lot of money but was overweight and unhappy with his life. Like Woo, he took a systematic approach to changing his life. Every week he does a “five-day water-only fasting protocol” and uses a variety of machines, including a glucose-tracking implant, to measure his metabolic markers. He has lost 60lbs from fasting and believes it has improved every aspect of his life.

Innovation or anorexia 2.0?

Dr Tiffany Brown, a postdoctoral fellow at UC San Diego Eating Disorders Center, told me over the phone that it can be difficult to make generalizations about when fasting behaviors and self-monitoring start to cross a line and become a problem. However, even if fasting diets may work for some individuals, Brown is worried about the extent to which it is treated as a “trend” and framed in a largely positive light.

The fact that we’re not all immediately describing Silicon Valley-style extreme fasting as a form of anorexia also says a lot about the gender dynamics around food and eating disorders. Anorexia is still very much associated with women and Brown notes that “people still have a difficult time recognizing similar behavior in men as problematic”. In her work with the National Association for Males with Eating Disorders Brown has met a number of men who said their friends, family and even medical providers, haven’t recognized their behavior as problematic, even when they look physically malnourished.

Dr Tiffany Brown is worried about the extent to which it is treated as a ‘trend’ and framed in a largely positive light

This isn’t to say that women don’t fast: a recent YouGov study found that 62% of men and 60% of women say they have fasted, up from 56% of men and 55% of women who said they had fasted in 2016. However, the most vocal proponents of the fasting movement seem to be men. Silicon Valley has also developed a pseudo-intellectual vocabulary that distances it from dieting’s “feminine” connotation. Tech types don’t diet, you see, they undertake “fasting protocols”. They don’t count calories, they quantify a range of metabolic markers with complex expensive scientific equipment. They don’t lose weight, they “optimize”. Rather than focusing on weight loss as a goal, they seem more likely to talk about improving their physical and mental performance.

Of course, drastically cutting calories in pursuit of a clear mind is not any safer than fasting in pursuit of a small waist. You can rebrand disordered eating, but you can’t remove its dangers. Longo worries that the “increase in irrational exuberance” around fasting in Silicon Valley may get gravely out of control, particularly with high-profile influencers like Dorsey publicly musing about potentially dangerous fasting experiments. “There needs to be more accountability,” Longo stresses. “Or this will all end up with lawsuits.”

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