By Daniel Burke, CNN Belief Blog Co-Editor

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(CNN) - After morning Mass on most Saturdays, you’d find the Rev. Dan Atkins cutting into a thick stack of pancakes or digging into a plate of eggs. But this Saturday’s menu is a bit spartan.

“I’ll probably just have coffee and a piece of toast,” said Atkins, the pastor of Holy Family Catholic Church in New Albany, Indiana.

The Catholic priest isn’t on a diet. Rather, he’s one of many believers across the country - and throughout the world - heeding the call of Pope Francis to fast and pray for peace in Syria on Saturday.

“It’s a way to be in solidarity with people who are suffering terribly from war,” said Atkins, a native of southern Indiana. “I’m going to be thinking about the children, the kids, affected by this terrible conflict.”

Holy Family is opening its doors Saturday afternoon and inviting parishioners to pray and reflect before the Blessed Sacrament, also known as the Eucharist, asking Jesus to bestow a blessing on the world. A special Mass for peace and and justice will follow.

“I’m going to be inviting people to stop and think: Is the world more peaceful this world because of something I did, or not?,” Atkins said. “It’s a way of bringing the pope’s message home.”

Pope Francis has proclaimed September 7 a churchwide day of prayer and fasting for peace in Syria. It was the first such proclamation since 2003, when Pope John Paul II called for fasting and prayer before the Iraq War, according to CNN Vatican analyst John Allen.

“Humanity needs to see these gestures of peace and to hear words of hope and peace!,” Francis said. He called on the world’s 1.5 billion Catholics, other Christians, people of different faiths and “all men of good will” to join him in prayers and fasting. Many are.

The Vatican expects to host huge crowds at its prayer vigil in St. Peter’s Square in Rome on Saturday evening.

In a poignant conjunction, U.S. President Barack Obama on Friday declared September 6-8 to be National Days of Prayer and Remembrance of the 9/11 attacks.

Obama encouraged Americans to remember the victims and their families through prayer, contemplation, vigils and other ceremonies.

The Catholic day of prayer and fasting is the spiritual component of a wider push by Francis and other religious leaders to persuade the United States not to use military force in Syria, even as they acknowledge the severity of suffering there.

In a letter to G20 leaders on Thursday, the pope decried the “senseless massacre” in Syria but said a military solution would be “futile.”

READ MORE: Pope to G-20: Keep your armies out of Syria

The U.S. Conference of Catholic Bishops echoed the pope, calling on Congress to consider this moral calculus: “Will more or less lives and livelihoods be destroyed by military intervention?”

According to the United Nations, more than 100,000 people have already died in Syria's bloody civil war, which has drawn fighters from Iran, Iraq and Lebanon.

In a letter sent to Congress on Friday, a coalition of Muslim, Christian and Jewish leaders organized by the Washington-based Friends Committee on National Legislation urged legislators not to approve the use of military force in Syria.

"Rather than yielding to the temptation to fuel the fire with more violence," the letter says, "we see an opportunity for the U.S. to leverage the full weight of its diplomatic influence and resources to advance a just, negotiated settlement."

Sister Patricia Chappell, president of the Catholic peace group Pax Christi USA, signed that letter and said she's combining protests with prayers on Saturday.

She’s fasting most of the day and joining a vigil at noon outside the White House with Catholic groups and other activists.

But if she wants to transform others, she must first be transformed herself, Chappell said, a process aided by fasting.

“It’s basically a way of cleansing myself and trying to be open to what God is directing me to say and do,” Chappell said.

In addition to the political advocacy, Catholic parishes from Alaska to Washington are holding prayer services and fasting on Saturday.

According to Catholic teaching, people who are fasting are allowed one full meal and two smaller meals. Ash Wednesday and Good Friday are obligatory fast days for Catholics ages 18 to 59, but the church occasionally asks members to fast on other momentous days as well.

READ MORE: Syria explained: How it became a religious war

Catholics aren’t the only believers praying and fasting for Syrian peace this Saturday.

Bishop Michael Vono of the Episcopal Diocese of the Rio Grande asked congregations in Texas and New Mexico to set Saturday and Sunday aside as days of “prayer, action and contemplation.”

The pope’s call to prayer and fasting is “too serious to ignore,” said Enuma Okoro, an author who has written several books about prayer. While granting the frailty of human faculties, human prayer has a quiet power, she said.

“Such things have been known to topple kingdoms, to bring down walls, to free those held captive, to heal and comfort, and to do what appears impossible for our limited imaginations,” Okoro said.

Even when prayer doesn’t move mountains (or mortar shells), it can still be worthwhile, said other Christians participating in Saturday’s spiritual campaign.

Rachel Held Evans, a popular Christian author and blogger, said she’s weighed the theological and political options, wept over images of disfigured Syrian children, sent money to help refugees and listened to the counsel of wise people.

And still, she said, she feels helpless. “It’s just so big, so complicated, so out of my control.”

But there’s a “strange power” in acknowledging helplessness before the divine and holding on to hope that God will answer, Evans said.

"In a world where opinions get whittled down to 140 characters and allegiances are declared on Facebook walls and 30-second TV spots, focused and deliberate prayer says: I don’t know. This is bigger than me. Help us, God.”

Like Evans, the Rev. James Martin said he has watched the news coming out of Syria with “growing alarm and sorrow.”

The Gospels say that when Jesus saw suffering, his “heart went out to them.” But that’s a weak translation of the Greek, said Martin, a Jesuit priest and prolific author. What the Bible really means is that it was gut-wrenching for Jesus to see people in pain. “That’s how I feel when I look upon Syria,” Martin said.

How do fasting and prayer help?

Abstaining from food forms a physical connection between the person fasting and people half a world away whose stomachs growl because they can’t find a safe place to eat, said Martin. Fasting puts our bodies in need, just as others do involuntarily.

As for prayer, Jesus famously said, “Ask and you shall receive.” Martin said he’s taking him up on that offer and asking for peace in Syria.

“How will God answer? I don’t know: I’m not God,” Martin said. “But I don’t need to understand God; I only need to be in relationship with God. I believe God hears us, so I pray.”

READ MORE: Syria's rebels: 20 things you need to know