The truth about fasting

In early 2020, Shiv Haria-Shah waved goodbye to breakfast. The London barrister and law firm partner had never really liked eating in the morning but, out of habit, he would grab a Bircher muesli pot from Pret on the way into work.

When the pandemic hit and he started working from home, however, Haria-Shah did a reset, thinking about ways to boost his “performance and wellbeing”. His executive coach, Kannan Paul, suggested he look into intermittent fasting. He started skipping breakfast and pushing back lunch so that no morsel entered his mouth before 2pm. He hasn’t looked back.

“I’ve found it pretty easy actually,” says Haria-Shah, 35, of his newish routine. On weekdays, he’ll consume only filter coffee, green tea and water in the morning; if he’s had a rich dinner the night before, he sometimes misses lunch too. He’s lost weight and, without the morning sugar high, is “definitely calmer”.

He likes the feeling that his body has “properly digested and made use of the nutrients” consumed the previous day before it is restocked, and appreciates the simplicity of only having to think about two meals daily. No, he does not often get “hangry”. “It feels like the natural balance for me,” he says.

There’s a good chance that many reading this share Haria-Shah’s sentiments. Intermittent fasting, a health practice that involves extending the time periods between eating, has been pursued by so-called biohackers such as Jack Dorsey and Bulletproof Coffee founder Dave Asprey for some time. And Michael Moseley’s decade-old 5:2 diet, in which you inhale barely a crumb for two days a week, has always had plenty of fans.

The concept of three meals a day is starting to feel quaint. Why did it become normal to starve ourselves for stretches of time?

But at some point in the past couple of years, the practice of missing meals has grown so common as to be unremarkable. On the of-the-moment pop culture podcast How Long Gone, the hosts, two regular “bros”, talk matter-of-factly about how they eat only at dinnertime.

The Intermittent Fasting section of the social network Reddit has more than 800,000 users feverishly comparing fasting durations. My mum, my friend’s aunt and too many friends to count now squash their meals into an eight-hour daily window, a method known as time-restricted eating that has emerged as the most popular form of intermittent fasting.

Not too long ago, if a friend mentioned that they didn’t eat in the morning, or on Wednesdays, you’d have cocked an eyebrow and considered an intervention. Now, the concept of three meals a day is starting to feel quaint. Why did it become normal to starve ourselves for stretches of time? And is it smart or simply unnecessary?

Kannan Paul, Haria-Shah’s executive coach, might be the dream ambassador for intermittent fasting. He’s whippet-thin, looks considerably younger than his 52 years, and has a soothing, monk-like presence (the buffed head helps).

Five years ago, inspired by Asprey, he stopped eating during the day; sometimes, he’ll fast for 24 or 36 hours. All four of his clients, who work in tech, finance or law, now practise some form of intermittent fasting too.

Like Haria-Shah, fasting feels natural to Paul. His father, who is Indian, has long preached about the power of fasting in accordance with Hindu traditions. (It’s also a staple of religions from Christianity to Islam.) More remote ancestors practised it too: early hunter-gatherers went for extended periods without food out of necessity. “In our 100,000-year evolution as a species, it’s only in the last 30-40 years that we have had food on tap,” says Paul.

The truth about fasting

As Tim Spector, the epidemiologist and author of Spoon Fed: Why Almost Everything We’ve Been Told About Food is Wrong, says: “We’ve been brainwashed into thinking when we wake up in the morning that we need something to put in our stomachs. If you only eat when you’re hungry, actually you’ll find that you eat several hours later.”

Nonetheless, the science has some catching up to do. Intermittent fasting has become “scientifically mainstream” to study and there’s “huge excitement” around its potential, says Courtney Peterson, a leading researcher on the subject at the University of Alabama at Birmingham. With almost 100 studies on humans — and many more on rodents — scientists are building a knowledge base. But, says Peterson, “there are still a lot of unanswered questions”.

There is ample evidence that intermittent fasting can help you lose weight. Practically, if you’re eating in smaller time windows, you’re unlikely to consume as many calories. But it goes deeper. One study Peterson was involved with indicated that, when people did time-restricted eating, it lowered their levels of ghrelin, the hunger hormone. This meant they naturally felt like eating less. Plus, after the 12-hour fasting mark, your body runs out of glucose so starts turning fat into energy. This ketosis process of “reducing bad fat” is one of the most compelling benefits, says Mark Mattson, a neuroscientist who hasn’t eaten breakfast in 40 years and has just published The Intermittent Fasting Revolution. (Some studies, including one from the University of California in 2020, have questioned its effectiveness for weight loss.)

Unlike fad diets that order you to hunt down frozen dragon fruit and activate your almonds, time-restricted eating asks only that you eat at certain intervals. It doesn’t care how much, or what, you ingest. “You don’t have to join Weight Watchers or buy special diet products: you can tailor it to your own lifestyle,” says Spector.

Fans say that gives it the most precious quality imaginable in a weight-loss regime: it is sustainable. Charlotte Lauren Wood, a creative content consultant in London, had “never been very good at dieting”. But, since late 2019, on four days each week, she has successfully squeezed her meals between 8am and 4pm. “I don’t find it that much of a sacrifice,” says Wood, 32.

Its appeal goes beyond keeping trim. For Paul, the most immediate benefit of eschewing breakfast and lunch is being “consistently quite sharp” across the day. Instead of “falling asleep at four o’clock” in a post-lunch slump, “you actually have an afternoon to work productively”, he says.

One of Peterson’s studies did indeed find that time-restricted eating increases energy levels and makes people less fatigued, although they’re not yet sure why (“it could be because eating and digesting food makes us feel tired, but it could be due to other reasons,” she says). But she adds that, in terms of overall health benefits, evidence indicates that eating two meals daily is preferable to just one.

There are also signs that intermittent fasting can lower insulin and blood pressure levels, improve gut function, increase the effectiveness of cancer treatments and activate a number of anti-ageing pathways. “The biggest debate right now is whether it has benefits [independent] of weight loss, or whether all the benefits are due to the fact that it helps you lose weight,” says Peterson.

Not everyone sees its potential. “I don’t promote it ever,” says Renee McGregor, a sports dietitian and eating disorder specialist who has worked with Olympic teams. “The research doesn’t stack up, particularly from a performance angle.”

She says it’s a myth that you will put down lean muscle if you exercise on an empty stomach.

“You don’t, because the body needs fuel to be able to turn that information into something useful.” Instead, you’re likely to have a lacklustre session and a poor recovery.

More concerningly, she has seen intermittent fasting “pre-empt” eating disorders in individuals who are genetically predisposed to such things. In some it can lead to binge eating in those windows; in others, the window for eating becomes ever smaller and “more and more restrictive” until eventually you get “the common traits we see with people in starvation: the fixation on body and the fear of eating. I’m not saying it will do this, but it can.”

In addition to people with an unhealthy relationship with food, Peterson says children, pregnant women, elderly people, and type 2 diabetics should avoid intermittent fasting. She believes that, “in the next 5-10 years”, the science will be solid enough to issue public health recommendations.

In the meantime, Haria-Shah thinks curious folks should try it. “Give it a go for a couple of weeks and, if it sits well with you, carry on,” he says. He’s convinced that getting his body off “the treadmill of consumption” was the way to go. “Unless the science suggests that what I’m doing is actually harmful, I don’t feel like I want to move to any other way of being.”

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