Whole-day fasting involves regular one-day fasts. The strictest form would be alternate day fasting (ADF). This involves a 24-hour fast followed by a 24-hour non-fasting period. The alternate day modified fasting (ADMF) and 5:2 diets—the latter defined as five days per week not fasting and two days per week either total fasting or modified fasting—both allow the consumption of approximately 500–600 calories on fasting days.[1][3]

Alison Moodie is a health reporter based in Los Angeles. She has written for numerous outlets including Newsweek, Agence France-Presse, The Daily Mail and HuffPost. For years she covered sustainable business for The Guardian. She holds a master’s degree from Columbia University’s Graduate School of Journalism, where she majored in TV news. When she's not working she's doting on her two kids and whipping up Bulletproof-inspired dishes in her kitchen.


This is probably a good time to mention that while I have practiced intermittent fasting consistently for the last year, I'm not fanatical about my diet. I work on building healthy habits that guide my behavior 90% of the time, so that I can do whatever I feel like during the other 10%. If I come over to your house to watch the football game and we order pizza at 11pm, guess what? I don't care that it's outside my feeding period, I'm eating it.
Several animal studies demonstrated that intermittent fasting based on daily circadian rhythms prevents weight gain. Mice given unlimited access to high-fat lab chow ate throughout the day and night which resulted in obesity and type 2 diabetes. Other mice fasted for 16 hours and actually consumed the same amount yet they didn’t gain weight or have negative health consequences. The findings suggest that it was the timing of eating, rather than the amount consumed which determined weight gain.
"There is a good evolutionary explanation for the difference in the calorie restriction response when comparing short-lived and long-lived species: famines are seasonal, and a season is a large fraction of a mouse lifespan but a small fraction of a human life span. Thus only the mouse evolves a relatively large plasticity of life span in response to food scarcity."

On my fasting days, I would wake up, have coffee, and start my day without any food. This would continue until about 5:30 p.m., when I would prepare a dinner that didn’t vary from my regular dinner in terms of either what or how much I ate. So, my fasting dinner would be something normal for me, like stir-fry, pasta, soup, sandwich, sushi, etc. This dinner looked like any other and occurred at the usual time. This made it simpler — I was just resuming eating with no special fanfare.
It doesn't matter when you start your 8–hour eating period. You can start at 8am and stop at 4pm. Or you start at 2pm and stop at 10pm. Do whatever works for you. I tend to find that eating around 1pm and 8pm works well because those times allow me to eat lunch and dinner with friends and family. Breakfast is typically a meal that I eat on my own, so skipping it isn't a big deal.
How It Works: Fast for 24 hours once or twice per week. During the 24 hour fast, which creator Brad Pilon prefers to call a “24 break from eating,” no food is consumed, but you can drink calorie-free beverages. After the fast is over, you then go back to eating normally. “Act like you didn’t fast,” Pilon says. “Some people need to finish the fast at a normal mealtime with a big meal, while others are OK ending the fast with an afternoon snack. Time it however works best for you, and adjust your timing as your schedule changes,” he says.
For example, in the graphic below you would eat dinner on Monday night and then not eat again until Tuesday evening. On Wednesday, however, you would eat all day and then start the 24–hour fasting cycle again after dinner on Wednesday evening. This allows you to get long fast periods on a consistent basis while also eating at least one meal every day of the week.
4) A sensitivity to God’s voice. The New Testament prophetess Anna is praised in the book of Luke for being a devoted servant to God and His temple. Because she regularly fasted and prayed, she was able to hear the voice of God speak clearly to her the day that Baby Jesus was brought into her temple to be dedicated. She knew He was the Christ and told everyone who would listen about His arrival. When we detox the spirit and become consumed with desire and praise for God, we become sensitive to His voice. Like Anna, when God speaks to us in the midst of chaos, we’ll still be able to pick out His voice and know what He wants us to do because we have trained our ear to hear Him through fasting, prayer, study and praise.

That means there’s certainly a type of person who won’t fare as well on it. “If you’re the type of person who wakes up ravenous, who loves breakfast, or who loves to snack, this may not be a good diet for you,” says Tinsley. “You won’t want to do something that makes it hard for you to adhere to. If this doesn’t gel with something you enjoy, you don’t need to fit yourself into this box just because intermittent fasting is popular right now.”
The fasting periods were often called ‘cleanses’, ‘detoxifications’, or ‘purifications’, but the idea is the same – to abstain from eating food for a certain period of time for health reasons. People imagined that this period of abstinence from food would clear their bodies’ systems of toxins and rejuvenate them. They were more correct than they knew.
When a feast day occurs on a fast day, the fast is often mitigated (lessened) to some degree (though meat and dairy are never consumed on any fast day). For example, the Feast of the Annunciation almost always occurs within the Great Lent in the Orthodox calendar: in this case fish (traditionally haddock fried in olive oil) is the main meal of the day.
IF might sound wacky to some, but there’s evidence that intermittent fasting for weight loss does work. One 2016 study in the Journal of Translational Medicine found that people who practiced IF for eight weeks lost more body fat than those in the control group. Another 2012 study from the Nutrition Journal suggests that IF can help obese women lose weight as well as lower their heart disease risk.
César Chávez undertook a number of spiritual fasts, including a 25-day fast in 1968 promoting the principle of nonviolence, and a fast of 'thanksgiving and hope' to prepare for pre-arranged civil disobedience by farm workers.[17][19] Chávez regarded a spiritual fast as "a personal spiritual transformation".[20] Other progressive campaigns have adopted the tactic.[21]
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