Choosing to Abstain

Advent today means the sparkling Christmas lights on Zurich’s Bahnhofstrasse, shops stripped bare, and mountains of online orders stacked in apartment doorways. Christmas markets lure visitors with their seasonal treats and mulled wine, and one festive dinner follows hot on the heels of another.

It hasn’t always been this way. Well into the 20th century, Advent was widely viewed as a “mini-Lent” – in contrast to the main period of Lent between Ash Wednesday and Easter. Known as the Nativity Fast, or Philip’s Fast, it remains an important tradition in the Orthodox Christian calendar today. The reason people fasted before Christmas was a question of simple economics, explains UZH theologian Ralph Kunz: “In a subsistence economy, anyone wanting to celebrate had to put something aside – if they didn’t fast, they couldn’t feast.”

In his new book, Kunz explores fasting as a spiritual and cultural practice. “Christians weren’t the ones to invent fasting,” he points out. They adopted it from Jewish and Greek traditions, where it was considered both spiritually and therapeutically beneficial. “Put simply: people already knew fasting helped.” This is why periodic abstinence is integral to many religions, as seen in the Ramadan month in Islam, at Yom Kippur in Judaism, and as part of meditative practices in Buddhism and Hinduism. The aim is self-examination, spiritual cleansing and deepened faith. Even during the Reformation, fasting remained important. While authorities had once set dietary rules, the Zurich reformer Heinrich Bullinger insisted in his Confessio Helvetica that fasting must be voluntary.

Religious roots aside, fasting has now made a comeback in its own right. Whether through intermittent fasting or detox retreats, periodically going without food has become a ritual in a society that prizes self-discipline. “Such heightened focus on the body is a megatrend,” Kunz says. But the motives behind this new movement differ markedly from religious ones. Instead of inner reflection, the purpose is self-improvement. People fast to raise their levels of performance, fitness and concentration – all in line with the success-driven logic of a consumer society.

“There’s this advertising slogan: Health is everything. That’s nonsense, of course,” Kunz says with a laugh. He warns against giving fasting undue moral or medical weight. If health is what ranks highest when fasting, the practice loses its meaning. For Kunz, fasting is above all a chance to pause – a tangible break from everyday habits that creates space for humility and attentiveness.

Anyone who chooses to fast commits to limiting or completely abstaining from food for a set period. “This firmness of resolve is already embedded in the original meaning of the word ‘fasting’,” Kunz notes. The time not spent preparing, cooking and eating meals becomes available for reflection, prayer or community. Social connection, he says, plays a crucial role. “Fasting doesn’t require people to withdraw,” he adds. “You can form fasting groups just as well.”

Similarly, food that goes uneaten can be donated to those in need or saved for social occasions. The true value of fasting as a spiritual practice lies in its blend of social, physical and spiritual dimensions. When fasting becomes no more than a diet, duty or competition in self-improvement, it’s being misused. “Fasting argues for a ‘less is more’ approach,” he says. “By choosing to fast, we resist the pull of consumer culture.”

However, this withdrawal is not just about liberation, Kunz adds. It forces people to face themselves. When you stop eating, you give up one of the easiest ways to distract yourself – and you’re left alone with your own thoughts. “Repressed or uncomfortable feelings come to the surface,” he explains. Fasting forces us to confront what everyday life usually keeps hidden.

Beyond these spiritual aspects, fasting also affects how the brain works. The outcomes of short-term fasting have been well-documented in numerous animal studies. “But we still have a research gap in humans,” says psychologist Lisa-Katrin Kaufmann, who is supported by UZH Alumni’s Research Talent Development Fund (FAN).

In her current project, she’s investigating how a short-term fast of 16 hours influences the neural mechanisms of stress processing. “After about 12 to 14 hours, there’s typically a shift in the body’s energy balance,” she says. “It switches from using carbohydrates derived from glucose to using ketones produced from the fatty acids in fat cells.”

In the FASTress study, psychologist Lisa-Katrin Kaufmann and her team are investigating how short-term fasting affects the neural and cognitive mechanisms of stress processing. The aim is to understand the biological processes that contribute to stress resilience. The project combines neurobiological measurements with psychological tests. The FASTress research team is currently seekinghealthy participants for the study.

In animals, this switch clearly alters their behavior and stress responses. “Mice become noticeably less anxious – they startle less at loud noises. They also act more boldly under stress,” Kaufmann explains. In elevated maze tests, a standard method for measuring anxiety, fasting mice showed less hesitation in exploring new areas. There was also evidence of a “dampening effect” in the brain – reduced responsiveness to stressors.

Whether the human brain also behaves differently depending on its energy resource, and whether fasting helps calm or stabilize the mind, is the subject of Kaufmann’s research. One hypothesis is that the body operates more economically during periods of food scarcity: “It seems plausible that the body wouldn’t waste additional energy on emotions that aren’t helpful in that moment,” she suggests. Emotional reactions may become more subdued, and the stress response may decrease. However, it’s important to note that these effects are short-lived: “If people go without food for too long, their risk of depressive symptoms increases.”

Hypothetically, short-term fasting may therefore function as a brief, calming mechanism – a neurobiological pause that prompts the body to conserve energy for what matters most. And this effect may be trainable. With practice in fasting, the body will get used to the switch and transition more quickly into ketosis – the process of generating energy from ketones, Kaufmann explains. “Figuratively speaking, intermittent fasting can be seen as metabolic training.”

Whether regular fasting periods might one day be recommended for therapeutical reasons – and in what form – depends on the study results. “Our goal is to observe how healthy fasting influences stress and anxiety and to draw insights for treatments,” she explains. Such insights could shape the way in which anxiety disorders and certain eating disorders are treated in future.

Whether seen as a therapeutic tool or spiritual exercise, both the theologian and the psychologist see fasting as a practice that links body and mind. Fasting interrupts the rhythm of constant availability. “In an affluent society, fasting is a challenge – but that’s precisely why it matters so much today,” Ralph Kunz says. Those who embrace it may discover an unexpected reward.

Perhaps deliberate abstinence is the key to unlocking what many of us miss during Advent: peace and reflection.