Fasting can be traced back to biblical times, with certain cultures fasting as a mental discipline to enhance spiritual awareness.
Intermittent fasting is still widely practiced today, with proponents of this lifestyle saying it can help people overcome weight loss resistance, reduce insulin resistance and consequently lower blood sugar – as well as possibly lower blood pressure.
Other experts claim that limiting caloric intake a few days per week through fasting can help improve neural connections in the brain and prevent plaque that accumulates in people with Alzheimer’s disease.
But how does intermittent fasting work, exactly? Is it safe, and what are the overall benefits for the right candidate?
This guide offers a comprehensive look at intermittent fasting for women. We’ve obtained input from several experts on this topic, who address everything you need to know about intermittent fasting, including what it is, how it works, the ideal candidate and potential benefits – as well as those who should avoid intermittent fasting altogether.
Keep in mind that this article is not intended as medical advice, so it’s important to talk to your medical provider before you try intermittent fasting.
- What Is Intermittent Fasting?
- How Does Intermittent Fasting Work?
- Intermittent Fasting Benefits
- What Science Has to Say About Intermittent Fasting
- Is Intermittent Fasting Safe?
- Best Candidates for Intermittent Fasting
- Worst Candidates for Intermittent Fasting
- Can You Work Out During Intermittent Fasting?
- How to Get Started with Intermittent Fasting
- A Sample Plan for Intermittent Fasting
- What to Avoid on Intermittent Fast
- How to Break the Fast
- How Does Intermittent Fasting Affect Hormones?
- Intermittent Fasting Throughout History
- Factors to Keep in Mind with Intermittent Fasting
Simply put, it’s switching back and forth between periods of eating and periods of fasting, according to Aaron Slotkin, a holistic nutritionist and owner of Holistic Nutrition by Aaron in Los Angeles, California.
“Examples are fasting during the daytime or for the whole day, 1 to 4 days per week, or several days per month,” said Slotkin, adding that this is not to be confused with calorie restriction, which is eating less food, every day.
There are a few different styles of intermittent fasting, noted Denise Canellos, owner of Canellos Nutrition in Irvine, California, who has a Master's Degree in human nutrition from the University of Bridgeport, and is an American College of Nutrition Certified Nutrition Specialist.
“One style is to take two days of the week and eat about 25% of your normal calories those days, and eat normally for the rest of the week,” said Canellos. “The other style is to go long stretches of the day, usually eight hours, without eating.”
How long, and what you can and cannot eat or drink, varies depending on the purpose of practice and safety of individual health, said Natalie Dawn Sampila, owner of Natalie Dawn Yoga & Ayurveda, who has been a yoga and Ayurveda practitioner for nearly 20 years and has utilized many varieties of intermittent fasting.
Ruth Pupo Garcia, a Registered Dietitian and Certified Diabetes Educator who works at Adventist Health White Memorial in Los Angeles, said usually the fasting state is considered 16 hours without food – then followed by eating all food within an 8-hour period, and then begin fasting for 16 hours again.
Intermittent fasting is also considered “purposeful fasting” during certain hours, said Julia Budniak, a Registered Dietitian with a masters in nutritional science, who coordinated a study on feasibility and safety of fasting-mimicking diets in 2013 at the USC Department of Gerontology.
“It's not dieting because it doesn't restrict any food groups outside of the time of fasting,” said Budniak, who works at Sports Academy in Thousand Oaks, California. “It’s limiting calories for a period of 8-12-24 hours. It can be easily adjusted to anyone schedule and preferences.”
Melina Ershaghi, a nutrition coach at DexaFit in Irvine, California, said intermittent fasting is quite simple.
“An individual should go 14 to 16 hours without any food – 3 to 7 days a week – and consume their energy needed for that day within a time period of 8 to 10 hours on recurring basis,” said Ershaghi.
For example, if your last meal is at 10 p.m., your next meal should be around 12 to 2 p.m.
“For people starting off this may seem difficult because many individuals start their day with breakfast around 7 a.m., but eventually within 2 to 3 weeks, the body becomes so accustomed to the fasting that you won’t feel those hunger pains in the morning – assuming your also eating enough the night and day before.”
Ershaghi has first-hand experience as someone who’s been doing intermittent fasting for five years, and has “seen great results from it.”
“I was diagnosed with Hashimoto’s four years ago…it is an autoimmune disorder that attacks the thyroid gland,” said Ershaghi, adding that the symptoms of Hashimoto's include fatigue, weight gain, low energy, dry skin, and hair loss.
“Intermittent fasting has given me a boost in energy, a reduction in body fat, and has helped my overall performance during my workouts and daily activities,” Ershaghi said. “Fast forward to today, and I am 99% cured due to my healthy lifestyle choices. I have read countless scientific journals on intermittent fasting as well as experimented on not only myself but hundreds of clients.”
During an intermittent fast, one typically will ingest water, coffee, tea, or a broth, said Slotkin, who added that during a fast day – typically for 24 hours – a person would consume water, coffee or broth for breakfast, green tea at lunch, then eat chicken, rice, and vegetable stir fry for dinner.
There are different styles of intermittent fasting, Canellos noted.
“On fasting days, people usually consume 500 to 600 calories, usually a mixture of two vegetables, 1 to 2 fruits, a small serving of grains and a small serving of protein,” Canellos said. “What people eat on the other days varies considerably.”
Sampila agreed that intermittent fasting can take on many forms.
“In the Ayurvedic tradition, if fasting is appropriate for your constitution…you do a kitchari cleanse or fast, where you remove all other foods and have a mono diet of kitchari,” Sampila said.
“This ancient recipe with basmati rice, mung dahl and spices such as turmeric, cumin, coriander, pepper and Ghee is ingested from 1 to 5 days with just water and teas. Mung dahl is easy to digest and helps move toxins through the body while building nutrients.”
This is only one of many ways, added Sampila, who has spent some time doing intermittent fasting by not eating past 8 p.m., and then waiting until 1 p.m. to have her first meal of the day.
“I use this method with many of my clients that are busy and won’t benefit from fasting for long periods of time,” Sampila said. “One could also do a broth-based fast where throughout the day or days you ingest liquid, which could include tea, and warmer broths which are always best as they are easier to absorb in the body.”
Garcia said an example of intermittent fasting would involve skipping breakfast – following dinner at 6 p.m. the night before – then skipping breakfast and eating lunch at noon.
“Most intermittent fasting regimens recommend sensible eating throughout the day after,” Garcia said.
When someone is transitioning into this new lifestyle, “I typically will say if you need to eat during the transition process, stick to cucumbers or celery until you can get used to fasting for the entire 16 hours,” Ershaghi advised.
When you want to break your fast with your first meal, you want to make sure to fuel your body with nutrients, she said.
“Your first meal of the day can be a breakfast or a lunch option,” said Ershaghi, adding that depending on the individual’s goal, you may choose either a high protein/low carb meal or high carb/high protein meal.
“It is best to eat a lower carbohydrate, higher protein diet paired with intermittent fasting and exercise for best health outcomes,” Ershaghi said. “During the hours that you can eat, it is always recommended to eat a healthy, well-balanced diet and avoid processed high sugar content foods.”
Ershaghi tells most of her clients to eat a diet that consists of leafy greens, moderate protein intake from sources like chicken, eggs, and turkey, carbohydrates from wild rice, sweet potato, yams, and brown rice, and finally, a variety of fruit.
“Eating a diet that consists of alkaline-rich foods and anti-inflammatory foods will give you the best results when paired with intermittent fasting,” Ershaghi said.
The positive effects of intermittent fasting can include overcoming weight loss resistance, reduction of insulin resistance and consequently lower blood sugar – and possibly lower blood pressure, according to Slotkin, adding that it can also increase energy and improve mental clarity.
Sampila feels feel there is great value in fasting one day a week with only liquids; especially if you carry a lot of weight, this habit might help to wake your digestive system.
“The benefits of intermittent fasting are weight loss due to the fact when the body is not getting an intake of food after 12 hours of fasting it starts to use stored fat – fasting can also help with muscle strength for the same reason,” Sampila said. “Fasting, it turns out, has a number of health benefits that most people seek, from improved cardiovascular health and reduced cancer risk, to gene repair and longevity.”
It’s been discovered that part of what appears to be driving the disease process is the fact that we’re eating too frequently, Sampila noted.
“When you’re in constant feast mode, your body actually forgoes much of its natural repair and rejuvenation programming,” she explained.
“Intermittent fasting effectively mimics the eating habits of our ancestors, who did not have access to grocery stores or food around the clock,” Sampila said. “They would cycle through periods of feast and famine, and modern research shows this cycling produces a number of biochemical benefits. In short, by altering what and when you eat, you can rather dramatically alter how your body operates. And that's great news.”
Garcia noted that according to Mark Mattson, a professor of neuroscience at Johns Hopkins School of Medicine, “limiting caloric intake a few days per week can help improve neural connections in the brain and prevent plaque that accumulates in people with Alzheimer’s disease.”
Regular fasting helps reduce insulin resistance by keeping insulin levels low, Slotkin said.
“The hormone insulin goes up anytime you eat food and helps escort glucose as well as other nutrients into the body's cells for energy – in obesity and Type 2 diabetes cells are insulin resistant,” Slotkin explained.
“Fasting, as opposed to just eating foods lower in starch, actually appears to improve insulin sensitivity. This helps correct the underlying metabolic imbalance.”
As far as weight loss, fasting depletes your stored energy in the liver and muscles – which is sugar called glycogen; as the body is depleted of glycogen it turns to fat for energy, therefore the fat burning process is activated, Garcia said.
Additionally, fasting, in particular, is stated as initiating an anti-aging process in the brain due to ketones, that are by-products of fat burning, being beneficial to our brain cells, Garcia noted.
“The theory is that fasting causes a challenge to the brain, and the adaptive response of the brain is coping with disease,” she said.
Budniak added that during an intermittent fast, “the body has time to regenerate, to fix your DNA, and do some repairs that it never has time to do when we digest all the time.”
Garcia noted one study published in JAMA Internal Medicine in which 100 overweight people were assigned to one of three eating plans: restricting calories daily by the same amount each day, fasting on alternate days, and normal eating habits.
“At the end of the one year study, both diet groups had lost weight compared to the normal eating group,” Garcia said. “The fasting group did not have any extraordinary results.”
In another study, the fasting group only was ahead of the conventional dieters by 1 pound.
“The studies that would support intermittent fasting are studies by Mattson, as his results are that cutting energy intake by fasting several times per week decreases neurodegenerative diseases like Alzheimer’s and Parkinson’s, and improves memory and mood,” Garcia noted. “Mattson claims that persons in his six-month study reported overall better well-being over time, and had anti-depression effects.”
According to Ershaghi, there have been many rat and human studies on the effects of intermittent fasting.
“A few studies have stated that intermittent fasting delays the onset of neuro-degeneration, reduces blood pressure, improves fasting glucose, reduces visceral fat, elevates ketone levels, resistance to diabetes, and reduces the risk for fatty liver disease,” Ershaghi said. “There is promising evidence that intermittent fasting can improve our resistance to disease.”
Shellee Dyne, a certified nutritionist at Dyneamic Nutrition in Calabasas, California, said there is scientific evidence about fasting.
“However, I do not suggest this as it’s hard to sustain and it can slow your metabolism,” Dyne said. “Healthy eating, exercise, 7 to 8 hours of sleep, and reducing stress consistently are the best options for the long-term.”
It varies by individual, according to Slotkin, who noted that people at any age can have a healthy metabolism or an imbalanced metabolism.
“I wouldn’t recommend any more than 3 days per week of fasting for a middle aged woman in good health,” Slotkin advised. He added that females are more sensitive to fasting than men, therefore extreme overeating after a fast may be common.
“Additionally, fasting can cause headaches or low energy,” Slotkin noted. “This is especially the case for those who suffer from low blood sugar.”
Fasting is not dangerous, Slotkin further emphasized. “I feel it is very safe. However, if one has any sort of medical condition they need to check with their doctor first.”
Women who are ill, have diabetes or pregnant should not use intermittent fasting, Canellos advised.
“The research we have shows that both styles of intermittent fasting appear safe as long as a woman is getting all of the nutrients she needs over the week,” said Canellos, further adding that as long as a person is not malnourished due to intermittent fasting, it does not appear to be dangerous.
If someone is using intermittent fasting as a way to mask an eating disorder or is not getting enough nutrients to stay healthy, that becomes dangerous, Canellos warned.
“If someone has a chronic illness, low blood pressure or diabetes they can experience adverse effects from intermittent fasting,” Canellos said.
For the most part, if you are healthy and not fasting for long periods of time, it is relatively safe, Sampila said.
“It is always a wise idea to have support or coaching from a professional that specializes in health and or nutrition,” Sampila recommended. “If you’re ever unsure and it doesn’t feel right don’t do it, or seek the advice from your doctor.”
It can be safe if it does not involve excessive calorie restriction for days, Garcia said.
“Each person is individual, in which fasting may affect timing and action of certain medications. For example, people with diabetes can suffer a severe low blood sugar reaction,” Garcia said. “If done excessively, very low calorie diets can weaken the heart.”
You have to find what works for you, Budniak noted.
“Start with small changes and fasts, maybe stop eating between 6 p.m. and 9 a.m. or do a day fast once a week,” Budniak said. “Don’t overdo it. For longer or daytime fasts, I wouldn't recommend more than 2 to 3 times week, so you don’t restrict too many calories and nutrients for your total intake.”
Budniak added that if it gets to the point that you obsess too much, restrict too many calories on too many days, “it can turn to disordered eating or even an eating disorder. Remember you're doing it for your health, not to have more health problems.”
There is little evidence whether intermittent fasting is harmful, said Ershaghi, adding that some people have paired intermittent fasting with calorie restriction.
“There is not enough data that has supported whether this is safe for long-term,” Ershaghi said.
This can, however, become dangerous if the individual is starving their bodies from nutrients and remains in a calorie deficit for a long period of time, she said.
“It is essential that you eat energy dense foods like avocados, almonds, walnuts, seeds, and nutrient dense foods like fruits and vegetables to prevent malnutrition,” Ershaghi advised.
Slotkin said the type of woman ideal for an intermittent fast is one whose blood sugar tends to run higher, has excess weight, and has inflammation and food sensitivities.
Other good candidates are women who are looking to lose weight, re-boot their body and mind, and release toxins from the organs due to unhealthy habits, Sampila said.
A healthy woman that is not on prescription medication or has a chronic condition, and does not have an unhealthy relationship with food, is also a good candidate, according to Garcia.
Additional candidates are women who don’t do well with dieting and calorie restriction, or those who have tried a lot of things and nothing worked, Budniak said.
Most women can adopt this lifestyle, Ershaghi added.
“There is no ideal woman, but many women who would like to see a decrease in body fat and would like to improve their overall health should adopt this lifestyle,” Ershaghi said.
Ershaghi always recommends women who restrict themselves calorically or do extreme dieting should not adopt this lifestyle because it puts their bodies in a state of metabolic stress and more health risks can occur.
“Also women who are pregnant should avoid intermittent fasting,” Ershaghi added.
A woman that suffers from any form of eating disorder, has a medical issue, pregnant or nursing, or suffers from hypoglycemia, should avoid intermittent fasting, Slotkin warned.
“If you get spacey or lightheaded when skipping a meal, or if you feel much better after you eat, fasting is probably not for you,” Slotkin said, “or at least until you heal your metabolism.”
Sampila noted that there are plenty of anecdotal reports from women who became amenorrheic – their menstrual period stopped – when they started doing intermittent fasting, then went back to normal when they stopped doing it.
“For these reasons, women should definitely be careful with intermittent fasting,” Sampila advised. “Ease into it, and if you have any problems like amenorrhea then stop doing it immediately. If you have problems with fertility or are trying to conceive, then consider holding off on intermittent fasting for now. Intermittent fasting is probably a bad idea when pregnant or breastfeeding.”
Budniak agreed that pregnant or nursing moms who need the calories for the baby development and milk production should avoid intermittent fasting, as well as women with diabetes who need to maintain their blood glucose.
“Not eating for long periods of time is not a good idea in that case,” Budniak said. “Anyone with any health condition should consult with a doctor before trying intermittent fasting.”
If desired, Slotkin recommends only some mild cardio, which can help elevate blood sugar, but he doesn’t advise weight training, which tends to lower blood sugar.
For individuals concentrating to lose fat, it is best to pair intermittent fasting with well-balanced nutrition – as well as exercise, Ershaghi said.
“I always recommend my clients getting at least 30 minutes of both aerobic and anaerobic activity at least five days a week,” Ershaghi noted.
If individuals would like to work out in the morning and are fasting, it is safe to do so if they have eaten enough energy the night before, she said.
“Keep in mind fasted workouts do burn through our glycogen levels more quickly, so individuals may burn fat quicker,” Ershaghi explained. “Making sure to re-feed with a healthy source of protein and carbohydrates after our workouts is crucial.”
She noted that many people during intermittent fasting also state that they see the best results when paired with High Intensity Interval Training, which is associated with a significant reduction in body fat and helps combat insulin resistance in young women.
“Also, a calorie deficit will affect an individual's energy level throughout their workouts,” Ershaghi said. “Many people are able to work out fasted, but others may have a harder time. I recommend experimenting with your body to see what time of day works best for you. Most importantly, always remember to listen to your body.”
It is best to start slow, such as one fast day per week, Slotkin advised.
A woman “should clear it with her physician first, then seek guidance from a nutritionist or dietician to make sure she is meeting her nutrient needs,” Canellos recommended.
Sampila emphasized that timing is everything.
“If fasting for the first time start slow and build,” Sampila suggested. “In reality, we fast each night when we are sleeping, hence that is where the term breakfast came: break fast.”
Her suggestion for women looking to try a fast: know what will and won’t work.
“If just reading this you’re getting mad, scared or hungry, start with a mono diet such as I mention above with the Kitchari,” Sampila said. “If you are looking for larger results other than a simple cleanse and reboot go with 3 days; it is never easy at first but hopefully the results of having more energy, a clearer mind and a little less weight will be inspiring.”
If a woman wants to fast, “I say first start slow,” Sampila added. “On day one, remove solid foods and just intake broth and/or teas. Choose to do your intermittent fast when you have time to do self-care. If your body has a lot of toxins from dietary or lifestyle habits, side effects of irritability, headaches and lethargy are quite normal.”
Additionally, beforehand, it is always good to start to cut down on refined sugars, caffeine, alcohol, and processed foods, because these all cause toxins in the body, “and once food is removed, the body will try and push the toxins out and can sometimes be very intense,” Sampila said.
“The magic day is usually the third day, whether intermittent fasting with liquids or a mono diet; for most women this is where they begin to feel energy and empowered.”
A woman should ask herself if this is a sustainable behavior for long-term weight control, Garcia advised. “Also she should consider how she feels when going without food for long periods of time.”
Budniak likes the “5:2 diet” where you choose 2 non-consecutive days a week and only consume 500 calories on those days.
“It's the easiest on your busiest days, but avoid strenuous exercise because you may feel a little more hungry after,” she said.
Dyne said she works better with routine, and so does Mark Mattson, a neuroscientist who's been intermittent fasting himself for the last 35 years.
“Mark Mattson suggests that in the morning you drink some tea or coffee and keep busy working until 1 p.m.,” Dyne noted.
If you usually exercise, then you may want to exercise at noon, she advised. Then eat a moderate amount of healthy food right after you exercise – around 600 calories – and eat the rest of your food during a 3 to 4 hour time window in the late afternoon to early evening.
“The biggest benefit is that your mind will be clearer and you will be more productive during the entire morning,” Dyne added.
Staying dedicated to any lifestyle change is crucial, Ershaghi emphasized.
“Once you incorporate fasting in your lifestyle, you will notice differences in your body within the first month,” Ershaghi said.
If you want to continue to get the health benefits of fasting it’s recommended to stick with it long term, she recommended.
“It’s always best to start slow and incorporate fasting 2 days a week and increase the number of days every 2 to 4 weeks,” Ershaghi said. “This will allow your body to get used to the change and allow yourself to gradually get used to fasting.”
Budniak offered the following example of fasting from 6 p.m. to 12 p.m. the next day.
“You simply don't eat during that time; water and decaffeinated beverages like herbal tea are okay,” she advised.
If you want to do intermittent fasting two times a week during your busiest days, you can eat a light breakfast consisting of:
- 1 egg
- 2 cups of spinach, ½ red pepper, ½ tomato, ½ onion, 5 sliced mushrooms
- 1 medium potato
Or a smoothie made with ½ cup blueberries, ½ banana, 1 cup of almond milk, 1 scoop of protein, and 1 cup of spinach.
“Both options are about 250 calories because the day will consist of 500 calories only,” Budniak said.
For dinner, she recommends a choice of a salad with 3 cups of baby greens or shredded lettuce, ½ tomato, 5 olives, 1 cucumber, ½ cup black beans, 2 tablespoons of Italian vinaigrette; or a soup made with 2 cups chicken broth (ready to drink or cubes dissolved in water), 1 package mixed frozen vegetables, and ½ cup plain croutons.
“Those are just sample meals, but honestly you can have any 500 calories that day,” Budniak said.
“I think it's easier to have it divided between breakfast and dinner because we tend to be the most busy between those hours anyways, so we won't think about food – it’s like forgetting to eat in purpose,” she said.
In this case, you can fast 10 to 12 hours, “so it's not a full day of no food, which I think makes it easier than a full day fast. Ideally, you still eat good, nutritious food, so your body is not deprived of nutrients when you don't fast.”
Canellos said that intense exercise should be avoided on fasting days; and Garcia advised to avoid all foods that have calories because usually during the fasting state, only water is allowed.
“As a woman, know where your challenges lie,” Sampila said. For instance, be mindful if you have a really busy work week, or parties or events that have options that won’t support your process.
“The goal is self care, and setting yourself up for success,” Sampila said.
Budniak advised to avoid long exposures to extreme conditions, “like heat and strenuous exercise because you may feel dizzy.”
It’s also important to avoid any pressure to get results, Slotkin said.
“The word diet can bring up negative feelings and also restrictive thoughts,” Slotkin noted. “Have the mindset that this is an experiment for fun, and it is simply a period where you skip eating every now and then. It is not about calorie restriction or avoiding certain foods forever, both of which may have negative metabolic or psychological effects long term.”
Slotkin advised to re-incorporate food as normal, as though you were not fasting beforehand.
“Any foods are fair game: oatmeal, chicken, vegetables, potatoes, oranges, avocados,” he said, adding that a regular sized meal should be eaten.
For intermittent fasting there are no restrictions on eating once the fast is over, Canellos noted.
“A woman should concentrate on consuming nutrient-rich foods to make up for any nutrient deficiencies from the fast days,” Canellos recommended.
Breaking an intermittent fast should be done consciously, Sampila emphasized.
“You will do yourself no favors if you go out for burgers and French fries,” Sampila said. “The idea behind intermittent fasting is to take charge of your health for the inside, so be mindful about what you are putting back into your body.”
Sampila recommends breaking your intermittent fast by introducing whole and healthy foods back into your system.
“I always think it’s best to cook it yourself if possible and that way you get a little love in the food as well,” she said.
Garcia said there are no eating patterns that she knows of that are recognized as a correct way to break a fast.
“Generally since hunger may be at an all-time high, overeating should be avoided,” Garcia said. “Also for overall weight loss success, a low fat healthy diet plan high in nutrients needs to be incorporated.”
The most important factor is to have an easily digestible meal, Budniak recommended.
“After your stomach had a break, the last thing you want to do is to overload it with heavy fried and greasy food,” Budniak said.
She recommends going for watery soups, a smoothie, lean protein like grilled chicken or fish, complex carbohydrates like quinoa, brown rice or potatoes, and plenty of vegetables without the heavy dressing.
“If it's your first time doing intermittent fasting, it is better if you have 2 smaller meals 3 hours apart after you're done to get used to eating and digesting again, then 1 large meal that may not make you feel so good,” Budniak added.
Intermittent fasting reduces the amount of the hormone insulin produced in the body, the main driver of weight gain, Slotkin said.
“This then allows the hormone cortisol to become more dominant which can then utilize fat for energy,” he explained. “However, females can be more sensitive to fasting and it may affect their menstrual cycle. For females, it is best to start very slow, like just 1 or 2 days per week of fasting.”
Intermittent fasting has been stated to increase HGH for men, but not women, Ershaghi said.
“There is also some evidence that levels of leptin and insulin are reduced,” Ershaghi noted. “Leptin is the hormone responsible for controlling our hunger and plays a role in caloric intake, fat deposition, and energy balance. Insulin is the hormone responsible for using the sugar from carbohydrates that you eat into your body’s cells for energy.”
Fasting can be traced back to biblical times, Garcia said, and certain cultures fast as a mental discipline to enhance spiritual awareness – one example is Buddhism.
In theory, our ancient ancestors practiced intermittent fasting all the time, Slotkin said.
“Why? Because food was not available like it is today,” he said. “As hunter-gatherers, periods without eating were undertaken, followed by periods of feasting. It is even theorized that fasting improves mental clarity since mental focus is needed during a hunt. Therefore, before an important exam or interview, it may be a good idea to avoid eating.”
Fasting has been around for as long as we have recorded history, Canellos said, with fasting for religious reasons the most common form.
“Orthodox Christians fast from animal products and reduce their food intake during Great Lent, Muslims fast from sunrise to sundown during Ramadan, and Jewish people fast from sunrise to sunset on Yom Kippur,” Canellos said.
Fasting for spiritual purposes is widely practiced, and remains part of virtually every major religion in the world, Sampila said.
“Jesus Christ, Buddha and the prophet Muhammad all shared a common belief in the healing power of fasting,” she said.
In spiritual terms, it is often called cleansing or purification, but practically, it amounts to the same thing.
“The practice of fasting developed independently among different religions and cultures, not as something that was harmful, but something that was deeply, intrinsically beneficial to the human body and spirit,” Sampila said. “In Buddhism, food is often consumed only in the morning, and followers fast from noon until the next morning daily. In addition to this, there may be various water-only fasts for days or weeks on end.”
Greek Orthodox Christians may follow various fasts over 180 to 200 days of the year, she continued.
“Muslims fast from sunrise to sunset during the holy month of Ramadan,” said Sampila, adding that the prophet, Muhammad, also encouraged fasting on Mondays and Thursdays of every week.
“So fasting is truly an idea that has withstood the test of time,” Sampila said. “Arguably, the three most influential people to have ever lived agreed that fasting is beneficial. If this was a harmful practice, do you not think we would have figured this out, oh, say 1,000 years ago?”
Prolonged and intermittent fasting was most certainly part of life during our evolution history, said Min Wei, who has a PhD in molecular biology and works at the Leonard Davis School of Gerontology at the University of Southern California.
“Our physiology has more likely been shaped and adapted to the prolonged/intermittent fasting,” Wei said, “and maladapted to the sustained and abundant food supply, the consequent over-eating, and a more sedentary lifestyle – all of which are fairly recent phenomena in the human experience.”
A woman should know what she wants to accomplish, and see if there are more effective means of reaching that goal, Canellos advised.
“She should be aware that on fasting days she most likely will be missing key nutrients and have a plan to replace those on the days she eats normally,” Canellos said.
According to Garcia, “she should evaluate her goal, and look at eating habits overall for sustainable results. Planning to decrease calories alone may not necessarily lead to sustained weight loss.”
Slotkin noted that eating real and unprocessed foods is the most important factor.
“Intermittent fasting will not save you from an unhealthy diet,” he said. “Unhealthy foods such as fast food will only backfire.”
Don’t try to catch up on eating just because you were fasting, Budniak advised.
“After you’re done, slowly resume normal eating without overloading your digestive system,” she said. Additionally, “make sure, you’re hydrated the whole time you fast.”
Dyne said to always check with your doctor to make sure fasting doesn’t affect any health problems you may have.
“Pregnant women, the elderly, and anyone with any chronic disease should not fast,” Dyne added.
Also, keep in mind that it’s normal to feel a tad of fatigue in the morning and slight hunger in the morning, Ershaghi said.
“But as you continue to keep this lifestyle going your body will adjust and you will start to feel a great amount of energy and your body can sustain longer hours without food,” Ershaghi noted. “Making sure to eat enough during the hours you can eat is crucial in order to avoid any hormonal and metabolic risks.”
Sampila added the most important factors to consider are:
- What is your intermittent fast going to look like?
- What is your purpose or goal for the intermittent fast?
- Is this a time when you can dedicate self-care?
- Can you set yourself up for success?
- Do you have support? Or are you willing to go at it alone?
“Be willing and open to the ups and downs, especially if you have to stop or cheat,” Sampila said. “There is no failure in trying.”
Intermittent fasting is an interesting idea, and Canellos said more research is needed before any recommendations are made.
“The threat of malnutrition is significant, and should not be ignored,” she warned. “There are thousands of phytonutrients that we can only get from whole, real foods – they are not available from supplements or meal replacement drinks.”
Intermittent fasting is not for every woman, and by no means makes you healthier than someone who eats and lives well, Sampila said.
“It is a tool that can be used to create a healthier body, eating habits and relationship with food,” Sampila emphasized.
“I feel the key for women is to connect with your intuition, work into it slow if this is your first time, or seek outside support from a health professional,” Sampila advised. “Never be afraid to ask for guidance or help.”
There are many ways to lose weight, Garcia said, but unfortunately most people regain weight that is lost due to lack of permanent lifestyle changes.
“Intermittent fasting is not exempt to this fact,” Garcia said.
We also must consider the neurological benefits of intermittent fasting, she said, however more studies are needed.
“Overall healthy eating habits along with more activity that is incorporated as a lifestyle has proven to aid in weight loss success,” said Garcia, adding that this is confirmed by the National Weight Control Registry, a national database of people who have lost weight and kept it off for 5 years or more.
“The question is: is fasting a temporary behavior, or a long-term lifestyle?” Garcia added.
According to Budniak, intermittent fasting is not a diet; rather, it's simply not eating and letting your body rest from digestion.
“I would recommend it to any healthy individual who cares about their health and longevity,” Budniak added. “Instead of forgetting to eat or skipping meals irregularly, try doing it on purpose. Athletes can do it, too, without compromising their performance, or losing muscle mass.”
To achieve the most out of intermittent fasting, it is best to stick with it for the long term, Ershaghi said.
“We are hopeful that this lifestyle can resist our bodies from disease and illness,” she said. “Remember to check with your physician before adopting any new lifestyle.”
» For Further Reading:
- Mediterranean Diet: A Comprehensive Beginner’s Guide
- Cancer Prevention Diet: 7 Foods That Can Lower the Risk of Cancer
- 7 Ways for Women to Lower Their Risk of Heart Disease