Sarah Oraby wakes up before sunrise to eat a meal every morning during Ramadan.

Once she is ready for the day, she fixes toast, a peanut butter and jelly sandwich or another food that is loaded with carbohydrates in preparation for the long day of fasting. She also makes sure to drink plenty of water to keep hydrated.

Thursday is both the beginning of the month of Ramadan and the day of Rosh Hashanah, which precedes the day of Yom Kippur by nine days. Both holidays that require observant Muslims or Jews to fast during the day. Muslims fast for a month, while Jews fast for Yom Kippur.

But abstaining from food and drink for 12 hours or more can take a toll on the body.

According to Jon Allen, coordinator for the nutrition program, it normally takes five to eight hours for the body to recognize that it has stopped taking in nutrients, which insulin regulates. When nutrients are no longer introduced into the body, insulin levels drop, and the body produces a hormone called glucagon, which regulates carbohydrate metabolism.

Carbohydrates produce glycogen, which muscles use for exercise.

When there are no more carbs left for the body to use for energy, it turns to body protein and fat for nutrition. When carbs are depleted, so are energy levels, despite the use of fat and body protein as a substitute.

Allen said that “this depletion normally results in fatigue, and the consumption of body protein can result in muscle atrophy.”

Ramadan, the ninth and holiest month of the Islamic calendar, is a 28-day period during which Muslims fast from sunrise to sunset. The Islamic calendar follows the lunar period, so the start of the 28-day month changes from year to year.

“In a way, you’re practicing self-discipline and self-restraint for the sake of God,” said Oraby, a senior in biomedical engineering and the president of the Muslim Student Association.

Not only do Muslims refrain from eating and drinking, but they also refrain from other behaviors they see as sinful, such as lying or cursing.

“[Muslims] also believe there are a lot of health benefits,” she said. “After a while of not eating, your body begins to clean itself … and the bacteria come out through your tongue.”

Allen said that ketones, byproducts of fat metabolism, are used as carbs when they are depleted. Ketones begin to appear in the blood, a process known as ketosis. After ketosis begins, the ketones can usually be found in your sweat and on your tongue and are expressed through your breath.

The main philosophy behind fasting is that “if you can stop eating or drinking, something you need to survive, then you can stop certain behaviors that you don’t need to survive,” she said. Oraby also said she doesn’t feel any different from normal when she fasts, other than the mild hunger and a slight fatigue.

Oraby breaks her fast by eating a couple of dates after sunset, a Muslim tradition. During the day, she craves “normal food, not fast food” and sits down at night to eat a three course, home-cooked meal that her mom prepares for her family.

Rosh Hashanah is one day out of the Jewish calendar year. Like the Islamic version, the Jewish calendar follows the lunar cycle. There are 10 days with Rosh Hashanah as the first and Yom Kippur as the last, the Jewish New Year and the Day of Atonement. Jews fast from sunset on the day before Yom Kippur to sunset on Yom Kippur.

During this day, Jews are usually in synagogue, where worship keeps their minds off of the hunger building up inside of them.

“When I was younger, I couldn’t fast for so long,” Jordan Robinson, a freshman in mechanical engineering, said. “Around 13 or 15, I was able to go on longer, but needed water.”

Robinson said he was able to fast all day after about 15.

Fasting does present a problem for athletes if Yom Kippur falls on a game day, especially since Jews have an incentive for fasting.

“It’s the day when God inscribes your name in the Book of Life for a good year or not,” Robinson said.

Robinson said he usually feels no effects of fasting, other than mild hunger, which is to be expected of such a short fast.

Allen said that effects of more prolonged fasting include lightheadedness, headaches and food preoccupation, “which can distract you from other activities — such as classes,” Allen said.