Fasting is not a new trend, although celebrities' embracing it as a method of dieting has brought the idea to the forefront recently.
In fact, fasting has, for centuries, been a way for followers of various religions -- including Buddhism, Christianity and Hinduism -- to observe their religions' holidays.
Now, some embrace fasting as a way to quickly lose weight or reduce or to become healthier, lessening their chances for diabetes or cancer.
In short term, they may be onto something, said Renee Waggoner, a dietician with Lourdes hospital.
"In the short term, for a lot of people, it really does help," Waggoner said.
In the long term?
"The camp is out," Waggoner said.
One of the more popular methods of fasting is the 5:2 diet, named such because those practicing this method eat for five days and "fast" for two.
"It's not a true fast," Waggoner said. "They still do get to eat something on those days: women get 500 calories and men get 500 calories."
Those calories should be spread out throughout the day instead of being consumed in one big meal.
And, on those days, dieters should seek healthier choices such as fruits, vegetables and small amounts of protein while staying away from high carb menu items and sweets.
"You still get all the minerals and vitamins you need, that way," Waggoner said.
Alternate day diet
A more extreme method, called the alternate day fasting diet, allows dieters to eat for 24 hours and fast for 24 hours, alternatively.
"On fasting days, they would drink no-calorie beverages and keep hydrated," Waggoner said.
She noted she didn't have much information on such a diet but "anyone with medical issues wouldn't want to do that."
The common theme
No matter what type of fasting a dieter may choose, there are a few suggestions common to any type that Waggoner suggests.
Most importantly, for those who are pregnant, diabetic or on medication, these types of diets may not be a good idea.
"As always, talk to your doctor before you do any of this," Waggoner said. "For those that are on these diets who are doing extreme workouts or a lot of physical activity, they need to be careful if they become light-headed or dizzy. They may not have had enough food."
Exercise, of course, is recommended with any type of diet, and she recommends that dieters exercise before their meals for the most success.
"You get a hunger surge 30 minutes or so after you exercise, so feeding then will help maintain diet," Waggoner said.
She also suggests, if you're counting the amount of hours you're fasting, include hours when sleeping.
While long-term effects aren't yet known, Waggoner said these types of diets have shown to help prevent certain health problems.
"In short term, these diets can seem to help with diabetes, cancer and heart disease, at least with those biomarkers," Waggoner said, explaining further that this is only for pre-diabetes.
She adds these types of diets tend to lead to more fat loss with less muscle loss, which she said is a good thing.
"They (dieter) will want to do more strengthening exercises, not so much cardio, to keep those muscles built up," Waggoner said.
The Academy of Nutrition and Dietetics, she said, hasn't come out against such diets so "there may be some benefits, but there's just no long-term studies yet. So, be cautious, which makes perfectly good sense."
For those who are uneasy about the unknown long-term effects or simply don't believe they could handle a fasting diet, there's always the realistic alternative.
"This sounds boring," Waggoner said. "But the best things to do is watch your portions: cut them down, use a smaller plate. Exercise. Reduce stress. All of those things build hormones. Also, be smart about what you eat. Sometimes pushing away from the table is the best way to diet."