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Intermittent Fasting for Weight Loss: What Does The Research Say?

Important: Fasting is not for everyone. Always consult with a qualified medical professional before making dietary or lifestyle changes. This information is intended to serve as educational material only and not to be relied upon for medical diagnosis or treatment.
*Most of the studies in this article were conducted on animals or men. If you are a female, please see the section below about special considerations for women and fasting.

What is Intermittent Fasting?

Intermittent fasting is the practice of cycling between periods of eating and periods of intentional fasting, or abstaining from food. Humans have fasted for millennia, whether for religious or cultural purposes or out of necessity during times of scarcity.

However, it’s a rare occurrence for most modern people to skip a meal when there are convenience stores on every corner.

Researchers are beginning to investigate how fasting intermittently affects weight loss and body composition. Unlike traditional “diets” that dictate what you eat, intermittent fasting focuses on when you eat, and it can be a powerful practice for better health.

Benefits of Intermittent Fasting

The benefits of fasting are similar to those of calorie restriction, which has been shown to have positive effects on weight loss and potentially even longevity. The problem is that for most people, counting calories is extremely tedious, requires a lot of guesswork, and is not sustainable. It tends to create a vicious cycle of losing weight only to gain it all back. Long-term calorie restriction without regular refeeds can be catastrophic for your hormones and lead to lower energy levels, loss of muscle or leave you feeling hungry and cold. Not fun.

That’s where intermittent fasting comes into play.

Intermittent fasting has been shown to mimic the benefits of calorie restriction without the potential drawbacks and the need to intentionally restrict food intake. Studies suggest that intermittent fasting is as effective as traditional calorie-restricted diets for weight loss due to specific benefits that occur during the fasting window:

Improved Fat Oxidation: Human studies have shown that fasting for periods of 12 or more hours can improve fat oxidation and induce mild ketosis.

Increased Metabolic Rate: Short-term fasting has been shown to lead to increased energy expenditure and metabolic rate in human studies.

Blood Sugar Regulation: Fasting can improve insulin sensitivity, lower overall levels of blood sugar, and reduce systemic inflammation, all of which are crucial factors for appetite regulation and metabolic health.

Normalized Appetite: Fasting has been shown to help regulate ghrelin, the “hunger hormone”. Ghrelin antagonizes leptin, the hormone responsible for telling us we’re satiated, so balancing the two is key to regulating appetite.

Better Muscle Retention: Intermittent fasting stimulates the production of growth hormone and testosterone, especially in overweight populations. These hormones help you maintain muscle mass while losing weight, and the more muscle you have, the more calories you burn at rest.

In addition to its benefits for fat loss, intermittent fasting has a host of other health benefits:

Autophagy: A repair process wherein cells dispose of damaged proteins and replace them with new ones. This process has been linked with anti-aging, longevity, and improved metabolic health because it keeps cells young and functioning optimally.

Improved Gut Health: Fasting can make your gut stronger by giving it a break from digestion, protecting it from the negative impacts of stress, increasing levels of good bacteria, and killing off harmful microbes.

Improved Blood Lipid Profiles: Fasting has been shown to improve a number of blood lipid markers including blood pressure, cholesterol, blood sugar, and triglycerides.

Improved Energy Levels: Most people equate hunger with lethargy, but fasting tends to lead to increased energy levels and cognitive function. This is due to increased fat metabolism and ketone production.

Intermittent fasting is a simple way to regulate energy intake without the need to weigh, measure, track, and count every morsel of food you consume. Many people find fasting to be an easier alternative to calorie-restriction for losing fat, increasing energy levels, and improving metabolic health.

Different Types of Intermittent Fasting

There are several different methods for intermittent fasting, each of which consists of different fasting and feeding windows to support different goals. Here are some of the most common types of intermittent fasting:

Time-Restricted Eating: This is a great approach for beginners. Time-Restricted Eating simply involves not eating between dinner and breakfast the next day. If you’ve ever gone to bed a few hours after dinner, gotten a full night’s sleep, and waited a few hours to eat breakfast, you’ve already done this type of fast!

  • Fasting Duration: 10-14 hours
  • What This Looks Like: If dinner ends at 8 PM, bedtime is at 10 PM, wake up at 6 AM, breakfast would be eaten between 8 and 10 AM. Only water is consumed during the fasting window – no other beverages and no supplements.
  • Frequency: Daily

16:8 Fasting: Also known as the LeanGains Method, 16:8 fasting involves fasting for 16 hours each day – as simple as skipping breakfast. This method is popular because a full day’s worth of food could be fit into the feeding window, making it easy to sustain long-term.

  • Fasting Duration: 16 hours
  • What This Looks Like: If dinner ends at 8 PM, eating would resume at 12 PM on the next day. Feeding could be compressed into an even shorter window of 6 hours after fasting for 18.
  • Frequency: Daily

Eat-STOP-Eat: Perhaps the simplest fasting protocol, the Eat-STOP-Eat method involves fasting for 24 hours once or twice a week. It’s highly effective for people who have a lot of weight to lose.

  • Fasting Duration: 24 hours
  • What This Looks Like: If dinner ends at 7 PM, eating would not resume until 7 PM the next day.
  • Frequency: 1-2x per week

Intermittent Fasting Guidelines

So, which type of intermittent fasting is best for you? The truth is that there is no one-size-fits-all answer: you must choose which method is the most sustainable for your lifestyle. Here are some guidelines that apply to all types of intermittent fasting.

How Long to Fast: The ideal length of fast depends on your what your body can tolerate.
Start with a short fast of 12 hours and work up from there by adding just an hour at a time.

How Often to Fast: Some people fast for 12-18 hours each day, others prefer less frequent fasts of up to 24 hours. The key is to choose a protocol that’s sustainable and fits effortlessly into your schedule.

What to Eat Before Fasting: Prior to your fast, have a reasonably sized meal with protein for satiety, fiber to slow digestion, and fat to provide you with slow-burning energy.

What to Eat to Break a Fast: You can break a short fast (12-16 hours) with a normal-sized meal comprised of healthy, whole foods. For longer fasts, consider starting with some bone broth and digestifs like lemon and apple cider vinegar to ease the body back into eating.

What to Consume While Fasting: Most experts agree that you should consume water and avoid significant sources of calories during fasting. However, even the top fasting experts can’t come to a consensus on what exactly breaks a fast. Dr. Satchin Panda believes that anything aside from water will break a fast, Dr. Jason Fung believes that zero-calorie beverages like coffee and tea will not break a fast, while Dr. Valter Longo’s Fasting-Mimicking Diet involves consuming small amounts of food while still reaping the benefits of fasting.

All of that conflicting information can feel confusing, but here’s a simple solution: instead of worrying about what “breaks” a fast, consider how what you consume can enhance or inhibit the benefits of a fast.

Here are a few other things you can consume to make intermittent fasting easier and accelerate weight loss:

  • Black Coffee and Tea: Caffeine can help suppress hunger and increase fat oxidation. The polyphenols in these beverages might even enhance autophagy during fasting.
  • Electrolytes: If you only drink water during your fasting window then you flush out electrolytes, which are vital for basic physiological functions. You can maintain electrolyte balance by simply adding 1 to 2 teaspoons of sea salt or supplemental electrolytes to your first glass of water each day.
  • Essential Amino Acids (EAAs): Though EAAs have been shown to inhibit autophagy, they can make fasting easier and more sustainable by suppressing hunger and cravings, improving energy levels, maintaining muscle mass, and supporting training in a fasted state. In other words, if your primary goal for fasting is to lose weight and improve body composition, EAAs will not negatively impact your fast and will likely improve your results. Look for an EAA formula (like Kion Aminos) that has minimal calories and is free of added fillers or sugars, as those components will take you out of a fasted state.

Listen to your body as you experiment with intermittent fasting. If you’re losing fat, feeling good, and performing well during your fasting window, then keep it going! If you find yourself feeling sluggish and see your weight stalling, then modify as necessary. Fasting has many health benefits, but it doesn’t always work for everyone. Remember to consult with your doctor no matter which protocol you choose!

Working Out While Intermittent Fasting

You might be wondering: can you work out while you fast? The answer is yes, and fasted training might even accelerate your fat loss efforts.

Here are some tips to maximize workouts during fasting:

Do the Right Training. If you exercise in a fasted state, opt for workouts that are easily fueled by body fat. Passive aerobic exercise like hiking or high-weight low-rep strength training are great options. It’s best to avoid intense anaerobic, glycolytically-demanding exercise like martial arts and CrossFit as glycogen will be depleted while fasting. This is especially true for women.

Take Time to Adjust. If you’re brand new to fasting, you might see a slight decrease in performance. You will adapt over time as your body gets used to tapping into stored body fat for energy.

Train at the Right Time. Women typically see more fat loss when they eat pre-workout and fast after exercise. Men, on the other hand, are more flexible but tend to see benefits when training fasted and having a post-workout meal.

Supplement With EAAs. Aminos acids increase fat oxidation during workouts and keep the body from cannibalizing muscle when taken prior to fasted training. Taking EAAs is also a potent hack for extending a fast post-workout, as they provide muscles with the proteins needed for rebuilding and recovery but allow you to continue burning fat until the next meal.

Intermittent Fasting for Women

Due to different hormonal profiles, women have to take some special considerations when intermittent fasting. For women, fasting creates a major reduction of Kisspeptin, which is a precursor to reproductive hormones. Therefore, fasting can lead to a significant decrease in sex hormone production in women, which can cause a whole host of symptoms including hormonal imbalances, loss of menstrual cycle, infertility, or thyroid issues. Women also produce less leptin than men, which means that they are more sensitive to hunger when food intake is restricted.

So, should women try intermittent fasting at all?

It depends. Fasting may not be a good idea for women who are very lean (under 18% body fat) and/or extremely active, have subclinical hypothyroidism, have hormone disorders, have a history of  eating disorders, or are pregnant, breastfeeding, or trying to conceive.

Healthy women typically do best with shorter or less frequent fasts, such as:

The Crescendo Method, which involves fasting for 12-16, hours 2-3 days a week on non-consecutive days. Ideally, fasting would fall on rest days as opposed to training days.

Eat-STOP-Eat, 24-hour fasts once every 1-2 weeks.

Occasional Prolonged Fasting, like a Fasting-Mimicking Diet or an Elemental Diet for 3-5 days, done 1-4 times per year.

Here are some other tips on how women can take advantage of the potent benefits of fasting without sabotaging their hormones:

Avoid intense exercise like CrossFit and long distance running during fasting. Opt instead for low-rep strength training, low-intensity cardio like hiking or swimming, and restorative movement like yoga.

Sleep, ensure you're doing everything possible to get plenty of quality nighttime rest.

Minimize stress, and prioritize relaxing activities.

Eat adequate calories from nourishing foods during feeding windows, including plenty of protein and healthy fats to optimize hormone production.

Intermittent Fasting Mistakes

Fasting can be a great tool in the right context, but it’s ultimately a stressor on the body. When combined with others stressors such as extreme calorie restriction, intense exercise, or stressful life situations, fasting might do more harm than good for your health.

Consider augmenting your fasting routine, or ditching it altogether, if you experience any of the following symptoms:

  • Irregular menstrual cycles or loss of period
  • Decreased fitness performance or recovery
  • Poor sleep
  • Negative changes to mood
  • Binge eating or uncontrollable cravings
  • Inability to lose weight
  • Acne or dry skin
  • Loss of libido
  • Always feeling cold
  • Thinning hair or hair loss
  • Infertility

Intermittent fasting should be icing on the cake of an overall healthy lifestyle. Make sure you cover your bases by eating nutritious foods, getting good sleep, exercising intelligently, and managing lifestyle stress before incorporating it into your daily life.

Common Concerns of Fasting

Will intermittent fasting make me lose muscle? Remember that intermittent fasting is more muscle-sparing than traditional dieting. You’ll only lose muscle if you don’t consume adequate calories (especially protein) during your feeding window. Strength training and supplementing with EAAs like Kion Aminos will also help support muscle maintenance during fasting.

Will intermittent fasting slow down my metabolism? Fasting has not been shown to reduce metabolism. Your metabolism won’t slow down as long as you eat enough calories during your feeding window.

Will intermittent fasting affect my thyroid? Fasting can cause a temporary reduction in thyroid hormone T3, which plays a role in metabolism and energy production. However, T3 production returns to normal once feeding is resumed. This re-uptake of metabolism and thyroid hormone is a benefit that is unique to fasting, as it doesn’t occur during long-term calorie restriction.

When do I take supplements during intermittent fasting? Most supplements contain insignificant amounts of calories and can be taken during the fasting window. However, some supplements are best consumed with food, including vitamins and fat-soluble nutrients. The best practice is to follow the directions on the packaging.

Safety, Side-Effects, and Special Considerations

Fasting is a great practice, but it’s not appropriate for everyone. Do not fast if you are underweight, under the age of 18, have recently undergone surgery, are pregnant or breastfeeding, or currently deal with mental health conditions. If you have gout, diabetes, or are currently taking prescription medication, then only fast under the supervision of your physician.


Intermittent fasting is quickly becoming one of the most popular and profound weight loss practices, and for good reason: it’s simple, effective, flexible, sustainable, and best of all, it’s free. Fasting can be incorporated into nearly any other diet and lifestyle with relative ease, especially with the help of a supplement like Kion Aminos.

Share your fasting stories, advice or questions below!

54 thoughts on “Intermittent Fasting for Weight Loss: What Does The Research Say?

  1. Hi Team Kion –

    I’m a male in my 40’s and have just started intermittent fasting (dinner at 7:30/8) and don’t eat my next meal until 10AM the next day. Just a couple of questions:

    1. While fasting, can I interchange every other day unsweetened almond milk 22g protein shake for breakfast and the other day two soft boiled eggs, 3 chicken sausage links and spinach?
    2. Should I take my daily three mile walk before or after eating my first meal?
    3. Can I eat lunch while fasting?

    Thanks for your help!

  2. I’m approaching 70 and am very lean; my BMI is 17.4; I workout daily, running, lifting, walking, yoga, tennis. I’ve been intermittent fasting for years now but I keep hearing seniors should not fast. I occasionally do a 38 hour fast about every 3rd month; normally daily fasts of 16-18 hours; my diet is good but I don’t have the muscle mass I use to have. Should I not be fasting? What are your thoughts on fasting for seniors.

    1. Hi Carrie, thanks for your question! Admittedly, whether fasting is a good idea or not really depends on the person. It seems as though you are very active, and also a female, so you fall into the two categories in which regular fasting may not be a good idea. Muscle mass does decline with age, so part of it may be a natural evolution. However, it can help to make sure you are doing a lot of strength training, consuming enough protein (along with digestive enzymes, as protein absorption declines with age) and calories in general, and supplementing with EAAs can support muscle mass as well. Fasting itself has not been shown to decrease muscle mass (studied in males), however, if you found that your muscle mass started declining when you began a fasting practice, you may want to re-evaluate the frequency and duration of your fasts. Consider changing your routine to something similar to what’s suggested in this article for women. Maybe forego the daily IF, or only do IF on non-active days, and instead do the occasional longer fasts. We hope this helps!

  3. While this is great information – it would have been even greater, as a woman, to have it addressed in the very beginning that the recommendations are for men and that there is a small piece for women at the end. Its a bit short sighted and myopic to write nearly an entire article as though it is for everyone when that everyone isn’t actually everyone. I am surprised Kion/Ben Greenfield wrote it in this manner – and I am sure it wasn’t intended the way it rolled out.

    1. Hi Noelle. Thank you for your thoughtful comment! We apologize that this article came off myopic and it was not intended whatsoever. Admittedly, upon writing this article we realized that a lot of the science available about fasting for women is not concrete, so we are hesitant to say that fasting for women is NEVER a good idea. Many females fast regularly and have no issues. However, we did want to include the caveat that it may not be the best choice for some females, and discuss the warning signs to look out for. We are considering writing a post on fasting for women specifically, and hope to expand on that topic in much greater detail. Until then, you’ll see we have added a note at the beginning of this article with the disclaimer you suggested. Thank you for pointing this out!

  4. Hello
    I have diadetes ,and im doing fasting 16/8 is safe for person with diadetes to do fasting also omega3 help in fat lost or omega 6 cla
    Than you

    1. Hi George, thanks for your question. Fasting with diabetes can be risky, so we definitely recommend asking your doctor for advice on this. Best of luck!

  5. I’m a 39 female and have been doing 16:8 hour IF for over 2 years and have experienced some amazing benefits. Mostly healing my gut from IBS and reduced food sensitivity. But I have been experiencing hair thining and hormonal imbalance. Would doing the EAA help with that? Also wondering if you could share your thoughts “dry” intermittent fasting? Thanks!

    1. Hey Anik, thanks for your question! Unfortunately, this happens for some women practicing IF due to female hormones being more sensitive to calorie intake. We are not doctors, but there’s a few things we would recommend. 1) Get your thyroid tested by a functional medicine doctor to make sure your levels are optimal. 2) Practicing IF daily is sometimes too much for some women. Try reducing the number of days you practice it to a few days a week, ideally on less active days. 3) Make sure you are consuming enough calories during your feeding windows. 4) If you are working out during the fasting window, especially HIIT, you might be putting too much stress on the body. 5) Maybe switch your protocol from Daily IF to a weekly or bi-weekly 24 hour fast to reduce the daily stress on the body.

      Hope that helps! And stay tuned for some more fasting information coming soon in the next week, specifically for women!

  6. Hi Ben,

    I have been practicing a 16:8 fast cycle for a few years now and it has worked great for me. I recently read Longo’s book The Longevity Diet, and while he is an advocate of fasting, especially his 5-day FMD, he recommends eating breakfast as skipping it may harden the arteries.
    Could you give your opinion on the pros and cons of skipping breakfast for my 16:8 fast, as I normally skip breakfast and eat between noon and 8pm but don’t want to do so if unhealthy.

    1. Hi Everett, thanks for your question! This is Team Kion, not Ben 🙂 We’d recommend taking a closer look at that study, as it doesn’t seem like skipping breakfast is a *cause* of atherosclerosis. The study itself points out healthy user bias, with the statement: Participants who skipped breakfast were more likely to have an overall unhealthy lifestyle, including poor overall diet, frequent alcohol consumption and smoking. They were also more likely to be hypertensive and overweight or obese. In the case of obesity, the study authors said reverse causation cannot be ruled out, and the observed results may be explained by obese patients skipping breakfast to lose weight.

      Therefore it doesn’t seem like this study alone would be enough evidence for that statement, especially if you are healthy and have healthy cardiovascular biomarkers. However, if you are experiencing poor sleep, weight gain, or low energy levels, you may want to reconsider the timing of your fasting window as eating earlier in the day may be better for circadian rhythm. We are also big fans of Valter Longo’s work and his FMD protocol, but it may not be for everyone. NOTE: We are not doctors, so please discuss with your health practitioner if you have any concerns.

  7. What about adding MCT oil to your morning coffee? I listened to Ben’s podcast where he said that putting the butter in the coffee would likely break your fast. But I read that since MCT oil is readily available and not digested by the liver, it would not trigger an insulin response and therefore keep you in a “fasting” state.

    The MCT oil helps me last until about 2pm before I actually eat a meal, just wondering if it still counts as fasting?

    1. Though MCT oil does contain calories, small amounts of it are unlikely to negatively impact the benefits of a fast, “small amounts” being the key modifier. Anywhere between a teaspoon and a tablespoon is unlikely to negate the effects of fasting.

  8. Theres so much contention on how to break a fast and ive read the kion guide multiple times. Recently a saw a well respected fitness and nutrition advocate, he’s had ben on his podcast before, discuss insulin resistance post fast. I do a weekly 24 and have usallt gone ben greenfield style and made a big ribeye and some sweet potatoes. This guy claims insulin resistance and that its bad to have any carbs of any type though? On non fasting days i have carbs at dinner to replenish my glycogen and for sleep. On my fasting days im working out with less intensity so i get that i need fewer carbs, but should i have lil to none? Especially if im working out hard the next day? I guess it also has to do with i heard you dont want to combine saturated fats, or high fat in general, with carbs too. In sum, full big meal with ribeyes, veggies, and starchy carbs post fast? Or skip the carbs? Thanks! Love the articles.

    1. The simple answer is to do what works for you. Carbohydrates are not inherently good or bad – some people do well with more, some people do well with fewer, others still do better with none at all. If you can tolerate the types and amounts of starchy carbs you’re eating, and you feel like they benefit your health and performance, then, by all means, keep them as a part of your post-fast meal.

      Check out our article on carbohydrates, fasting, and carb refeeds for a more detailed look at the role of carbohydrates in an otherwise low-carb diet.

  9. When would you recommend taking Kion Aminos if I’m fasting 16/8? First meal is at noon and I train at 4pm. I’m currently taking them post workout.

    1. Timing depends on your goals. If you’re using them for the sake of recovery and muscle-building, then continue to take Kion Aminos post-workout. You can consider taking them pre-workout to boost performance, but that’s likely unnecessary since, assuming a quality protein source was part of your 12 PM meal, you likely still have amino acids in your system.

      You can also consider taking Kion Aminos in the morning before breaking the fast if you find yourself feeling hungry or fatigued.

  10. Taking Kion EAA’s made all of my discomforts go away (Hip pain, lower back pain, shoulder pain’s) while fasting, do you happen to know this is?

    1. Kion Aminos are supportive of muscle protein synthesis and overall recovery. The benefits are especially powerful when combined with the benefits of a fasted or ketogenic state.

  11. I have been doing 20 to 24 hour fasts daily for the past month. I am eating 1 or 2 meals a day and trying to eat at a caloric deficit as I am trying to a large portion of weight. In the last month I have lost about 20 lbs and have another 40 to go. I am running about 3 miles every day and weight training a couple days a week. My issue is that I am having a hard time eating enough calories in my 1-2 meals. I am shooting for 2200 calories and may eat 1200- 1500 or so. I feel great, I am losing weight but fear I that it is not healthy to eat so little calories. Any input on this?

    1. When maintaining such a restricted eating window, it can be very helpful to have things prepared in advance. Including caloric/nutrient-dense beverages (think bulletproof coffee, antioxidant rich smoothies, high quality bone broth, etc) can also be effective in helping cover some gaps.

  12. With regard to your contention that “women produce less leptin than men”, the study you cited suggested that females have HIGHER leptin levels per unit fat mass. The gender differences within the study did not indicate one gender producing more or less leptin than the other, but rather that fat mass was the best predictor of serum leptin concentration in men, and body fat percentage was the best predictor of serum leptin in women. Therefore, in both men and women, adiposity is related to circulating leptin levels.

    Other than that, this was one of the best-written articles out of many that I have read on the internet concerning the benefits, types, and caveats of intermittent fasting.

  13. I’ve been doing an intermittent fasting. Mine has been a little bit different though.
    I eat a breakfast at about 430 am., and drink only water throughout the day (one half my body weight in ounces). My morning meal consist of 4oz of chicken, 1 soft boiled egg, about 8-10oz of frozen fruit that I put into the boiling water I took my egg out of. Then pour out most of the water and put in oatmeal. Then I don’t eat again for 14-16 hours.
    Pretty much all I eat for dinner is 8oz of chicken, 8oz of fresh or frozen veggies like peas or green beans and a half cup of pre cooked rice. Before bed two tbsp of peanut butter. The chicken is canned chicken breast with rib meat, drain the broth and rinse in hot water, 120% of the daily allowance for protein. I’ve cut my carb intake to half to one-third the daily allowance. Sugar intake below the daily allowance. And my total calorie intake is typically at or just barely over 1000 calories. Sometimes up to but never over 1300 calories per day.
    Have lost 12 lbs in the last five weeks and I have plenty of energy and fill great. I run 1-2 times per week. 3-4 times per week if my IT BAND Syndrome isn’t bothering me. So about 10-20 miles per week or 50-100 miles per month.
    What would be your best recommendations for vitamins and suppliments to help aid in weight loss and retaining and/or gaining muscle mass. I don’t workout much yet but when I start, I only want to tone up. I love to run.

    1. It would be smart to increase your food intake during your feeding window. Such a low amount of calories for an extended period can be deleterious your hormones, potentially causing negative side effects and actually make it harder to lose weight/support lean muscle mass. In general, Kion Lean would be excellent support for blood glucose regulation and energy metabolism. Essential amino acids (like Kion Aminos) help to support lean muscle mass, aid in recovery and are crucial for muscle protein synthesis

  14. in his interview with kevin rose, valter longo says intermittent fasting puts you at an increased risk for gallstones. he also said that skipping an early breakfast increases your risk for heart disease.

  15. Thanks for the article! Especially the part about women fasting. I’ve been doing IF of about 16 hours daily with a low carb diet and yes, it messed up my period and I experience hair loss. I guess I will do less of it and see if my problems go away. I will add butter to my morning coffee.

    I keep meaning to ask, what do you think about microwaves? Ok or not? I bring lunch to work and the only way to heat it up is to microwave.

    1. Microwaves have been shown to diminish the nutrient content of food and can also cause plastic to leach into your food… It would be best to use alternates to plastic containers (ie. glass) to heat your food if you have to use the microwave.

    1. We can’t comment on all medications, but as long as you are not strict fasting most supplement/meds (save those containing significant amount of calories or sugar) will not diminish most of the benefits of fasting

  16. I have a question for Ben. Recent diagnosis of osteoporosis of the spine. I have no symptoms and feel quite strong.

    50 years old, female, clean eating- lots of greens, fish, bit of meat. Supplements – aminos, magnesium, thorne – citrate with calcium. D3 QUESTION What else can I take to deal help? Stem cell injections?

    vit D great, cortisol is high due to work stress
    calcium 9.7 anion Gap 7, CO 27, K+ 4.6, NA 140
    low thyroid under control via Nature Thoyd
    glucose level 89 – good
    HDL – good 216
    LDL – very low 101
    Try glyceride 44
    HDL-C mg 97
    Non HDL c 119
    cortisol 23.3
    Creatine .6- good
    ALT 19
    AST 21
    ALP 45

    more calcium – increase from around 500 to 1000?
    I already do daily yoga, walking with weights, swimming, etc

    injections in the spine with stem cells?
    specific food?
    take estrogen- estrogen is low but I get nauseas when I try to take natural pathetic estrogen

  17. do you consider hypertrophic training while intermittent fasting to be intense exercise? is it possible to gain muscle mass while intermittent fasting? is it even advisable to eat in a caloric surplus with intermittent fasting?

    and can eating a large quality of food — even low glycemic — over a short period of time — say around four thousand calories in about four hours — itself have any inflammatory digestive consequences, or affect nutrient absorption?

    also, you said that black coffee might enhance autophagy while fasting, and elsewhere have talked about coffee stimulating lipolysis during exercise. but is any of that dependent on whether or not black coffee will spike your blood glucose?

    and though you advise those with mental health issues not to fast, you also note the role that fasting can play in gut health. given that for many a leaky gut is likely the cause of their mental health issues, and given that intermittent fasting can help heal a leaky gut, would it not be advisable for them to consider intermittent fasting as part of their approach to getting better?


    1. Regarding fasting and hypertrophy:

      1. Hypertrophic training doesn’t necessarily constitute intense exercise, but it depends on how you approach it and what your training plan is. For example, doing traditional bodybuilding workouts of 3-4 sets of 8-12 reps at a moderate weight might not be overly intense, whereas high-weight 20-rep squats or constant training to failure might be too much. Consider supplementing with amino acids to fuel intensity and maximize the efficacy of your hypertrophic training.
      2. It is possible to gain mass on a fasting regimen. If that’s your goal, you can indeed eat at a caloric surplus and reap some of the benefits of fasting.
      3. Eating at a caloric surplus in itself can have inherent consequences on digestion. Eating in a condensed window is unlikely to affect nutrient absorption, though this depends on several other factors including overall gut health. Note that the smaller your feeding window is, the harder it will be to take in adequate nutrition to gain mass.

      For more on combining fasting with mass gain, we suggest you look into The LeanGains Method by Martin Berkhan.

      In regards to coffee, autophagy, and lipolysis: If coffee spikes your blood glucose, then it could potentially affect autophagy. It depends on the severity of the spike.

      Regarding mental health: We are not doctors and thus cannot speak to specific treatment. Those struggling with mental health conditions should consult with their physician to determine if fasting could be helpful for them.

    1. Exogenous ketones are unnecessary during fasting. The exception is during fasted training. wherein a combination of essential amino acids and exogenous ketones can help fuel intense workouts.

  18. I have been doing 20-24hour fasts every day for about a month. I wonder if it is good or not for me. Sometimes i feel like I’m starving. I’m very lean and do hot yoga and workout every day also. ive always had stomach issues and i feel like they got better. Sometimes i get too full after i eat my big healthy keto meal. I just don’t know if i should be fasting every day like that or not. I’ve been listening to dr bergs one meal a day method. Thank you so much for help and i hope to hear from you

    1. You might be stretching yourself too thin, especially if you’re already lean. It might behoove you to decrease the frequency and/or duration of your fasts. See the section “Intermittent Fasting for Women” in the article for our recommendations.

  19. Ok this was perfect for me! I was doing some extended fasts ( only 24 hours) after daily intermittent fasting while trying to stay in ketosis and keeping my daily lifting protocol. I started very quickly to feel bad. Even though I had high energy I felt sluggish which sounds like the opposite but it’s hard to explain. Additionally, I wasn’t seeing any weight loss of the 5 lbs that I was targeting. So I added some carb cycling and reduced my fat intake from 80% of my calories to 60% and I feel better!

    I’ll try some of your suggestions above

  20. Under Train at the Right Time.
    “Women typically see more fat loss when they eat pre-workout and fast after exercise. Men, on the other hand, are more flexible but tend to see benefits when training fasted and having a post-workout meal.”

    How long should a woman fast after a workout? Say I get up have 100 calories a chia slurry, then run 5 miles at a zone 2 pace. How long should I fast post-run?

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