Updated on Feb. 27 at 9:30 a.m. ET.

No booze. No meat. No french fries. For millions of Christians around the world, 40 days of “fasting” kicked off on Ash Wednesday, marking the beginning of Lent. In the United States, even as younger Americans drift further away from organized religion, the practice of Lent persists.

The Lenten season culminates on Holy Thursday, which falls during the week before Easter Sunday. (This year, Lent runs Feb. 26 to April 9.) Those observing — including Catholics and many Christians in liturgical traditions — historically fasted or refrained from eating meat, especially on Fridays, or gave up other luxury items, such as sweets or fatty foods. Resisting temptation was meant to be a time of reflection, an opportunity to grow closer to God.

In 2015, 47 percent of U.S. Catholics said they gave up something or did something extra for Lent, according to the Pew Research Center. One-third of cultural Catholics said they would observe Lent, as did 12 percent of former Catholics.

Millennials are leaving religion in greater numbers than ever before, but they are more likely to observe Lent than baby boomers, according to 2014 research from Barna Group, an evangelical Christian polling group. Twenty percent of millennials (those born between 1981 and 1996) responded that they were planning to fast, compared with 10 percent of boomers (those born between 1957 and 1964).

And increasingly, “fasting” is being adapted for modern times. What millennials choose to give up aligns with other current movements — environmentalism (going vegan, for example), an awareness of the pitfalls of technology (forgoing social media) and a commitment to social justice causes (volunteering). For those who did observe Lent, according to the 2014 Barna Group research, giving up social media, phones and video games was especially gaining in popularity.

For Elizabeth Harper, who is in her 30s and identifies as Catholic, Lent is an opportunity to reflect on “some of the ways I’ve legitimately sucked as a person and ways I can make the world just a tiny bit better by going through a small, uncomfortable confrontation and correction,” she wrote in an email.

Harper, a professor living in Los Angeles, is taking her reliance on technology a step further in her nuanced fast. In order to acknowledge what she called “the erosion of workers’ rights” that have come with the convenience of smartphone apps, Harper has, for the past few years, doubled her tips to restaurant workers during Lent.

This year, she also decided to keep cash on hand and give some amount of money to anyone who asks. For Harper, who described herself as “shy,” the aim of this year’s observance is twofold: “I was inspired by something Pope Francis said a while ago, that not only should you give to people who ask without question, but it’s the human interaction that goes with it that’s important,” Harper wrote. “I think that’s an area where I’ve been deficient, and this is an opportunity to do better while still keeping my focus on the larger injustices in the world, not just my own self-improvement.”

These days, those abstaining in the lead-up to Easter might not even be religious.

Writing in Talking Points Memo in 2015, Monica Potts made “The Case for Secular Lent.” She wrote: “Lent forces you to think about what you’re eating, why you’re eating it, and whether it’s tied to your goodness as a person. It provides an opportunity to believe you can start fresh.”

Potts, who no longer considers herself religious, argued that Lent could be as divorced from religion as Christmas:

“A lot of nonreligious Americans, who tend to be young and urban-dwelling, must find this humanistic quality to Lent appealing.”

For those who aren’t religious but want to start new habits, Lent has the benefit of commencing right as people are realizing that their New Year’s resolutions have lapsed.

“The timing is right for people to start worrying again about self-improvement,” said Wendy Wood, a research psychologist and the author of “Good Habits, Bad Habits.” “By the end of February, people may be willing to try again to change their unhealthy, unproductive behaviors, and Lent could be an opportunity to do so.”

Google “Lent weight loss,” for example, and an endless number of plans or challenges come up.

Toronto-based writer Anne Theriault, 36, refers to herself as a “bad Catholic,” because she disagrees with the Church’s teachings on various social issues.

Still, she’s giving up tea for Lent.

“It’s probably a very middling thing to give up, because it’ll be an inconvenience, but it won’t feel like a huge sacrifice. Someday I’ll give up social media or alcohol,” Theriault said.

Still, for those who are observant, the secularization of Lent for self-improvement isn’t the point.

“It’s really not about personal health, and it’s definitely not about looks,” Harper, the Catholic professor, said. “I don’t think St. Catherine of Siena was after a bikini bod.”

Editor’s Note: This article previously misstated Elizabeth Harper’s name.

Our days are full of uncertainty. We asked religious leaders for guidance on making it through.

Their wisdom could help us weather these times

The unexpected life of a millennial nun

Armed with degrees and work experience, these women are going against the grain of their generation