Is Fasting Really a Safe Way to Lose Weight?

by Trinh Le, MPH, RD
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Is Fasting Really a Safe Way to Lose Weight?

Think of a time when you wanted to lose weight. Naturally, you knew to eat less, but how much less depends on your metabolism, which determines the total calories you need throughout the day. Eating fewer calories than you expend typically leads to weight loss, but how you want to budget these calories gets very personal.

While most of us prefer a consistent calorie goal, some find it helpful to slash calories through intermittent fasting. Intermittent fasting is skipping meal(s) for a certain number of days with the purpose of creating a calorie deficit for weight loss. On the days you don’t fast you have the freedom of a higher calorie goal to eat with.

Let’s be clear: Intermittent fasting is not:

1) Going more than 24 hours without eating.
2) Regularly eating a very low calorie diet (think: less than 1,000 calories for women and 1,200 calories for men).

Both these scenarios can lead to nutritional deficiencies and other health complications and are not something you should pursue without the help of a health professional. Now that we have that straight, let’s jump in:

Defining Fasting for Weight Loss
Intermittent fasting allows you to shift the calorie-cutting phase of your weight loss to a couple of days per week as opposed to every day. It works because you don’t need to cut calories daily to lose weight. You can go under your goal one day and over the next but still lose weight if you eat fewer calories than you burn.

It’s important to note not all fasting diets are the same, and that something as simple as skipping a meal can count as fasting. Here are a few different ways people practice fasting that don’t include religious fasting:

  • Complete alternate-day fasting: Fast every other day. A fasting day means no calorie-containing food or beverage for up to 24 hours. An eating day allows you to eat as much as you want.
  • Modified fasting: Fast just a couple of days per week. For example, the popular 5:2 diet schedules 5 days of eating freely with 2 days where calorie intake is 20–25% of needs.
  • Time- restricted eating: Eat freely as you feel hungry throughout the day, but only within a specific window of time. For example, setting up a window of 12 hours and only eating within that time frame. Skipping breakfast and not eating after dinner counts as time-restricted eating.

Source: Table adapted from “Intermittent Fasting and Human Metabolic Health” from the Journal of the Academy of Nutrition and Dietetics.

Are Fasting Diets Better than Nonfasting Diets?
A 2011 review by Krista Varady, PhD, at the University of Illinois at Chicago examined 11 daily-calorie-restriction and five intermittent-fasting studies. As an FYI, “daily calorie restriction” is how we’re traditionally taught to cut calories: cutting a consistent but small amount of calories every day. Varady found that both methods of cutting calories were equally effective at helping healthy subjects lose weight and fat, but intermittent fasting appeared to offer an added benefit. Those who practiced intermittent fasting preserved more lean mass (90% weight lost as fat, 10% weight lost as muscle) than those who followed the more traditional method of daily calorie restriction (75% weight lost as fat, 25% weight lost as muscle). Because lean mass burns more calories than fat mass, it is beneficial to help you lose fat while preserving as much muscle as possible.

While these numbers may look impressive, there are a few drawbacks to this review:

  • Not enough studies exist. The review included just 16 studies—there just weren’t many studies addressing intermittent fasting. Because of this, there were disproportionately more studies for daily calorie restriction—11 daily calorie-restriction studies versus five intermittent-fasting studies.
  • Small sample sizes. Study sample sizes were small, ranging from 8–173 subjects, with most studies hovering at 20 subjects.
  • Difference in measurement techniques. Most daily-calorie-restriction studies use dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) to measure fat mass while most intermittent-fasting studies use bioelectrical impedance. Because DXA and MRI are more accurate at assessing fat mass compared to bioelectrical impedance, it makes it difficult to conclusively say that daily calorie restriction preserves lean mass better than intermittent fasting.

The science isn’t perfect, but it confirms what we already know: weight loss happens when the calories eaten are less than calories burned. If you’re overweight or obese, both nonfasting and fasting weight loss can lead to similar health benefits that’ll make your doc proud! Just a 5–10% weight loss can help bring down pesky numbers on your blood test (think: cholesterol, blood pressure and blood sugar).

Is Fasting a Safe Choice for Me?
The answer really depends on how you approach it and how your own body responds. As mentioned before, going long periods of time without eating, or eating a very low calorie diet for extended periods of time, is not safe. Generally speaking, though, the human body is designed to deal with periods of fasting. If you’re a healthy adult with weight to lose, there’s little evidence to say that intermittent fasting isn’t safe.

However, fasting isn’t for everyone and you shouldn’t try it if you are pregnant, diabetic or healing from a traumatic event like surgery. Still iffy about whether fasting is a good choice for you? We suggest seeking guidance from a health professional before experimenting.

5 Tips for Fasting
If you want to experiment with fasting to switch up your weight-loss journey, here are a couple of tips:

  1. Log your calories. If you’re doing a modified fast, you may want to track calories on a fasting day to help you meet your target calorie goal. For all other fasts, it’s helpful to track calories on the days you eat freely. Doing so can help offset the likelihood you’ll overeat and thus cut into your overall calorie deficit.
  2. Take it as an opportunity to better understand hunger. Not surprisingly, fasting diets can bring unpleasant side effects, one of which is hunger. We’re all born with hunger cues to signal that our stomach is empty and we should eat. For most of us, this ability becomes blunted as we age especially in a plentiful society where food is not in short supply. We may even mistake thirst or cravings for hunger. Fasting can reacquaint you with what physiologic hunger feels like.
  3. Drink plenty of water. Depending on how long your fast is, your body may switch to fueling itself more from fat and protein instead of carbohydrates. To do so will require more water to keep your metabolic machinery running smoothly. Also, if you’re already feeling minor unpleasant side effects from hunger, you don’t want to add a dehydration headache to the list!
  4. Choose nutrient-dense foods. On eating days, choose nutrient-dense foods that pack plenty of important vitamins and minerals along with calories. Nutrient-dense foods include fruits, vegetables, whole grains, dairy, lean meats, seafood, nuts—you get the idea! These are foods you should choose even if you’re not fasting. Check with your doctor if you’re concerned about vitamin and mineral deficiencies or want to undergo an extended fast longer than 12 weeks.
  5. Know you can always change your mind. Tried fasting and found it’s not for you? Fasting isn’t for everyone, especially those who get hungry really easily. Just know that you can cut calories the old-fashioned way and still lose weight.

SOURCES

  1. Varady, K. A. 2011. “Intermittent Versus Daily Calorie Restriction: Which Diet Regimen Is More Effective for Weight Loss?” International Association for the Study of Obesity 12(7): e593-e601. Accessed August 30, 2015.
  2. Patterson, R. E., G. A. Laughlin, A. Z. LaCroix, and S. J. Hartman. 2012. “Intermittent Fasting and Human Metabolic Health.” Journal of the Academy of Nutrition and Dietetics 115(8): 1203-1212. doi: http://dx.doi.org/10.1016/j.jand.2015.02.018. Accessed August 30, 2015.
  3. Orenstein, B. W. 2014. “Intermittent Fasting: The Key to Long-Term Weight Loss?” Today’s Dietitian 26(12): 40. Accessed August 30, 2015.

Related

  • Ana

    It is so refreshing to see a MFP blog post with real information. Thank you, you did an amazing job writing this article. Nothing bothers me more than when MFP spews crap about “starvation mode” and “you aren’t losing weight because you’re not eating enough”.

  • Ajarn Ron

    Anyone who hasn’t figured out how to lose weight has to on another planet by now. Calories in/calories out. No tricks needed.

    • shrity

      calories in calories out could you be more specific pls sounds good

      • Ron Leroux

        Calories in ( how many calories you consume in a day). Calories out ( how many calories you burn in a day, rest, exercise). If you burn more calories than you consume you WILL lose weight. On the other hand if you consume more calories than you burn you WILL gain weight. Finding out that number can be tricky. You can use Calorie burned calculators on line to help you as a guide. I myself fasting everyday. It’s great! I don’t eat breakfast. As I am not really hungry. Only a cup of black coffee, or green tea. It allows me to eat a bigger lunch and dinner without feeling guilty. I am on a cut (losing fat) right now. So I consume 800 calories for lunch, and between 1000-1400 calories for dinner. I burn about 2,800 a day. Calories in (1800-2200). Calories out ( 2500-2800). So my calorie deficit will be anywhere between 1,000 and 600. I personally have 1 day a week where I eat at maintenance (2500-2800 calories). Helps to revamp my metabolism and keep me mentally focused on my weight loss. Feel free to add me on facebook. Ajarn Ron or Ron Leroux.

        • Whoknows

          You’re spot on. It’s not rocket science. My IFing consists of a fast between 9pm-1pm. I only have coffee in the morning. I used to do the “6 meals/day” and it was a nightmare. It’s so much easier to prepare when you only have to figure out 2 meals/day.

        • stuck

          That’s great for those of you who can exercise normally. My body is messed up from multiple back surgeries and I live in constant pain on a daily basis. I take 2 short walks a day, drink a protein shake for breakfast & lunch and then try to eat a healthy dinner. I have gone to PT and end up in even more pain. So what are the suggestions for someone in my condition? I would love to be able to exercise but cannot. I have gained so much weight because of it. I’m not a big eater but just can’t lose weight. The fast thing sounds like a solution, maybe…

        • ron6788

          Not as easy as it sounds. It’s often very difficult to pin down ‘calories out’. Apps help but there’s a lot of factors: age, type of work, exercise habits, genetics, weight and frame type, etc. ‘Calories in’ are easier to figure because they’re the same for everyone but still every single bit of food one eats has to be measured, looked up, and logged. This whole business is not anywhere near as easy as you’re making it sound. Then, there’s side issues, such as the quality of the calories and how much that matters, and how much a person will burn in after-effects from HIIT workouts and from being muscular.

          It’s a little annoying to hear people talk like it was so simple. If it were, there wouldn’t be hundreds of books out there on dieting and millions of people struggling. Lastly, even if we do know what’s good for us, can we actually do it?

    • Roseanne McKinley Knowles

      AMEN!!

  • Ramehu

    Fasting with natural homemade fruit and veggie juices is the best way to detox the body and lose weight without feeling hungry. I’ve been doing that for over a decade once or twice a year. I usually do 10 days and once I did 21 days but now I am doing 30 days.

    • Victoria Rejuney

      Detoxing in this sense isn’t recognised by science. It isn’t a real thing that actually happens to the body.

  • all carefully…

  • Moran Zhou

    As Big Brandon Carter would say, IF allows for satisfying, luxury meals while maintaining a calorie deficit. Quality over quantity.

  • Naim Khan

    I’m glad people have realised the benefits of fasting, at long last. Of course Muslims have been fasting for a month each year for the past 1500 years! I fast regularly, still work a normal day and then go to the gym in the evening. On average I lose about 4kg weight during that month.

    • Naomi Lynn

      You are right, the Jews have been fasting for 5000 years. (the muslims of course copied it from them)

      • Islamophobia

        wow….

    • Mohan

      There were no muslims 1500 years ago-And there shouldn’t be any soon. Its a fking radical cult.
      Anything good attributed to muslims (Algebra, architecture, fasting…) is a joke. The only thing they really are good at is terrorism-and that too they copied from the Tamil Tigers.

  • Anne Sisley

    I cannot believe this article was posted on a trusted weight loss source like Myfitnesspal. This mindset of fasting is what hooked me as a teenager and led to an eating disorder. “Fasting” is what we called it when we skipped a day of eating but guess what we called the days we ate? “Bingeing”. That’s all this is. These ideas can become a toxic mindset that can very easily lead to health and mental problems. Just reading this article triggered me, and made me think maybe I should stop eating again, an idea that I fight against every day. Who’s to say an impressionable teenage girl isn’t reading this right now and feeling as though the ideas she’s been toying with about not eating are now justified and validated. Shame on you, Myfitnesspal.

    I want to encourage everyone reading this thinking it is a safe option for weight loss to close out immediately and go eat a healthy balanced meal that you love.

    • Naomi Lynn

      I have been intermittent fasting off and on for a few months now. But since it is difficult, I only do it 3 days a week.

      It works for me I don’t eat from 8pm – 2pm. I also do my cardio in a fasted state. It burns fat like crazy. Also, I do not lose muscle.

      Sorry it does not work for you. I think you have been doing it wrong, or do not accurately understand what IF is.

      • highlatte

        Not eating food 6hrs a day is not fasting. 8pm-2pm?

        • cq13fish

          8PM-2PM is 18 hours of fasting, not 6.

          • highlatte

            Sleeping is not fasting time, not in the medical community. So assuming you don’t sleep right before bed and sleep hours not near 18 hrs. Nice try.

          • momof3

            Say it isn’t counted. She is still not eating 10-12 hrs a day. If sleeping isn’t fasting time why do I wake hungry? If u eat before bed your body Works on digestion during sleep. If you don’t, your body does not work on digestion…it focuses on repair… just like daytime except night digestion may lead to more stored energy.

          • highlatte

            Okay, one more time for those of you with no experience opinions only: Eight to twelve hours is considered fasting, doing a daily fast not eating from rise till bedtime is considered fasting not sleep time as we are not meant to sleep and eat at the same time. Talk to your doctor, I’ve worked for a number of them. btw missing a meal or two is also not ‘fasting’ it is skipping a meal. Enough.

          • momof3

            I am not clear on your ‘no experience opinions’ comment. I have worked at as a bioscientist at a medical research college until deciding to be a SAHP and have always known knowledge and experience are often not one in the same. Perhaps you should additionally consult journal articles and organizations like NIH rather than only the opinions of doctors with whom you have worked. I am sure they are trusted opinions, but opinions none the less. I think everyone agrees upon the definition of skipping a meal. That is silly. However, that does give a glimpse into the disregard you gave the facts which I presented. I have fasted overnight for 3 c-sections… in my Doctor’s orders. Even the ‘wiki’ community has the definition of fasting correct. It is irresponsible to spout out opinion as fact. I tend to offend people with my comments because they ‘lack’ smiley faces and such. I really just make statements that are not meant to be muddied by emotion. Being more analytical rather than empathetic, I do so enjoy these forums.

        • gdavissd

          No, you are mistaken, that is 18 hours

          • highlatte

            Sleeping is not fasting time, not in the medical community. So assuming you don’t eat right before bed and sleep hours not near 18 hrs. Nice try.

          • Ty C

            No, sleep hours count.

            I mean unless you’re a sleep eater it’s still fasting.

          • Dick Tracy

            The word for our morning meal “breakfast” means to break your fast, sleeping counts. I have fasted one day a week for over ten years. There are many benefits beyond weight control, primarily a rest for our digestive system and toxin elimination. Drink the proper amount of water for your weight, 24-36 hour fast will benefit you greatly

    • Abigail Mueller

      I totally agree with you. I’ve always loved and trusted the content on Myfitnesspal and because of this article I’m discussed! I was shocked as I read the article. I’m no longer going to connect myself with Myfitnesspal. You really should be ashamed!!!
      -abby

      • highlatte

        Actually the article is very informative. Your opinion is uneducated opinion only.

      • AnnaF

        You need to read up on how fasting works.

      • Dick Tracy

        Be serious, I’ve fasted one day a week for over ten years. Don’t be so easily offended.

    • Rizzo Rizzo

      Sorry for your struggles, but science supports the safety and efficacy of intermittent fasting. Bingeing is not part of any IF protocol.

      Do the research prior to adopting a new eating plan and carefully consider the risk/reward ratio as it applies to your specific situation. IF may not be a good fit for those who suffer from an eating disorder, but it can offer a wealth of benefits for the right person.

      Best wishes.

    • Elizabeth CW

      I had a similar response. I saw the title and expected to see a rational explanation of the risks of this form of dieting and some advice on a natural and balance approach to nutrition. I was shocked to see myfitnesspal actually promoting it and even giving advice for people to try it. Anne, I also believe that it is a form of disordered eating, and I commend you for speaking out about it. People definitely need to hear the other side of the story! Like Abigail, I will not trust myfitnesspal in the future.

      • Dick Tracy

        See ya, keep your head in the sand

    • Judy

      Anne – The article clearly states fasting is not for everyone and only if you are healthy … I would think mentally as well as physically, too. I would expect that if you consulted your physician, based on your health history, he would have advised against it. I am one who will actually gain weight if I had to force myself to eat three square meals plus two snacks a day. I was always 5-10 lbs overweight all my life. Now at 68 y/o, I’ve lost those excess pounds by one of the fasting methods above and I’ve lived a pretty sedentary life, too. Please do not malign fasting for healthy people. It does work!

    • Carol

      Anne, I am in agreement with you and I respect your courage and determination to overcome. I have great concern for young adults that are looking for answers – this is HIGH RISK. Final thoughts, most people don’t know they are at risk for an eating disorder until they enter into fasting. Similar to many addictions I would think.

      • highlatte

        Fasting does not create eating disorders! No diet or method does. Wanting to practice diets and methods obsessively means you already have a disorder. I wish you people with no medical training or experience would stop spreading uneducated opinions. btw Fasting does not mean ‘not eating’ that is anorexia, learn to understand terminology, at least.

    • highlatte

      Anne, you were looking to feel and be in control; the fasting did not lead you to eating disorder nor does any other diet or weight loss regime. A number of cultures and religions practice healthy fasting. The idea that we must have food in our stomachs at every moment is a false one that leads to obesity, diabetes, cravings, inflammation, and bowel disorders. Healthy minds are not obsessed with eating or not eating, as a former bulimic I know that help from others both professional and personal is important. Fasting two days a week has reduced my appetite and the inflammation of RA in my body, also, my bowels are more regular. It does take a change in mindset and a want to let go of obsessions. The biggest yes-yes for weight and health is to ‘eliminate’ processed sugar; this alone ( but not only) will reduce unhealthy pounds and inflammation.

      • Miya McDougall

        I agree, I also had anorexia and bulimia. It was more of a control issue for me but everyone is different. This has worked out great for me and my weight loss after having 4 babies in 5 years!

    • Pat

      There are other things that create eating disorders although I’m sorry for your struggle this information isn’t flawed. There’s no one size fits all solution. Fasting for religious purposes as well as weight loss is a way of life for some people. Having a healthy awareness of self is what’s important when considering any diet or exercise program.

    • ron6788

      I agree with you, Anne. It’s dangerous when you start messing with a natural function. Skipping meals is a short term easy way to drop a few pounds but a terrible long term practice. The body will canabolize itself for fuel and use muscle protein and you don’t want to lose muscle.

      • RMBolderson

        Actually the very opposite is true. Intermittent fasting has been shown in studies to lead to less muscle loss than regular daily caloric restriction.

      • Dick Tracy

        Really? What if you eat 1000 calorie meals? It isn’t about the number of meals, but the amount of calories

    • Dick Tracy

      Don’t be so easily offended, the vast majority of society will benefit from a weekly fast. I have for over ten years

  • Brenda Grabowski

    I am a 56 year old female who over the last approximately 10 years has gained 30 pounds even though I am working out more than ever and cutback back on my calorie intake. I go to the gym (and have for more than 30yrs faithfully). I simply cannot lose weight.I am5feet tall and weight 130 lbs. Has anyone gone through this?

    • Michelle Gorski

      I was ill and gained weight when I was 55. I had fasted before from one to three days. I decided to go on an extended juice fast and I lost 30 lbs in 42 days. I’m 64 now and have never gained the weight back. Any time I gain five lbs I go on a short fast and it’s gone.

      • Brenda Grabowski

        Thanks although I think a juice cleanse would be difficult. Which one did you follow?

        • Michelle Gorski

          i just made my own raw juice fruit juice in morning and vegetable juice in the afternoon. Did lots of different combinations. I also took whole food vitamin supplement to make sure I didn’t miss any vitamins. After the 1st 3 days your digestive system shuts down and your appetite goes away. The hard part is after the fast. Adding solid food back into the diet slowly to not over taxing the system. I read lots of books before I started and then listened to my body.

    • sandra

      I am 63 and just the same, i cannot lose weight. I went along to my health centre and saw a nurse, who by the way was double the size of me! She said i would never get the weight off as i had gone through the change, etc! I came away thoroughly disheartened and fed up. Yes i can relate to what you are saying as that is me now. I dont know what the answer is but please do not do this daft fasting lark, i doesnt work and it leads to health and mental problems. I dont know how they dare print it.

    • Nancy

      Brenda I real your pain!! Am in the same boat. Am 63 & have gained 20 lbs from menopause. Eat gluten free, eat healthy & exercise 5-6 days a week. Have tried every combo to get the weight off. More calories, less, IF. It takes me a month to maybe loose 1 pound. People think it is just soooo easy to lose weight but for some like us it is not!! MFP says I should be loosing from what I am doing but there the scale sits. Thank you for the article. Good info. Good luck Brenda!

      • Lisa Phillips

        You can get it from GNC.

    • Teri

      I gained 30 pounds in 4 months when I started going through menopause. I waited until it was over, then went on the HCG diet (homeopathic spray version), lost the weight and have kept it off. I too had tried traditionally calorie cutting with exercise and nothing worked except this.

      • Brenda Grabowski

        Thanks for your reply. I will try anything at this point. Where did you find this?

    • Nannie Ann

      Brenda, this seems pretty common as we age. Metabolism slows down as estrogen decreases, I understand. I have been doing 500 calories on two non-successive days each week for a couple of years. The theory is that it confuses your metabolism and increases it. My experience post menopause was exactly like yours, and increasing my exercise didn’t seem to have much impact. I had lost about 20 pounds with Weight Watchers but with a job then that involved a fair amount of business travel and entertaining customers, it was just hard to keep losing. I’ve lost another 10 pounds with the 2:5 calorie reduction and it’s VERY easy to keep it there. 500 calories is not as hard as you’d think, but like any new plan, it takes some study to find your way. The best part for me is psychological…when I see something I really want on a 500 calorie day, I tell myself I can eat that tomorrow. Delayed gratification but not by much! Like any ‘diet”, it works better for some that others, but it’s worth a try. Good luck!

  • Joyce

    I love IF. It’s the only thing that has worked for me.

  • disqus_e3b0l4oMNS

    I tried the 5:2 and it worked for about six months quite well, but I found that when I began eating normally again, the weight boomeranged back and I haven’t been able to get it off since. I feel like it encourages overall unhealthy eating practices, and don’t recommend it.

    • SweetArlene

      IF is a way of life, not a diet. If you go back to unhealthy eating habits, of course you will gain all the weight you lost. It’s simple math.

  • sandra

    What a load of tripe! Who at MyFitnessPal thought this was a good idea to put it on the internet? I would like them to stand before me and i would give them a piece of my mind! Stupid! It just leads to health problems and mental problem. Get a grip and stop feeding us this crap!

    • Readuponhowfastingworks

      You’re an idiot.

  • AlisNwonderland

    I’m confused. There is literature that says your body chemistry goes into “starvation mode” when you fast, holding onto the calories you do ingest because “it thinks” it may not get fed again. As I understand it, that’s part of the thinking behind “small meals frequently”. Any enlightening thoughts?

    • JofJLTNCB6

      Every time someone uses the phrase “starvation mode” incorrectly, a puppy dies.

      Why do you hate puppies????

    • Cris Anderson

      ‘Small meals frequently’ has to do with insulin production. Not ‘starvation mode’. The thought process (and the marketing punch…don’t fool yourself into thinking 6 small meals a day is about health. Also, keep in mind this is over simplified to make it short and understandable) is that by eating six small meals you’re keeping your insulin production to an even low, which supposedly helps limit fat production. However, using that logic, intermittent fasting STILL wins. Your body can only produce so much insulin at a time. So, I don’t eat all day…no insulin production right? My TWO meals per day within the same short time window can only spike my insulin production so high, and only for a limited window of time. MY ‘two large meal’ average insulin production for the day will be less than someone who at six smaller meals.

      As for ‘starvation mode’…’as understood by the unwashed MFP masses…well, it’s a myth. Going a day without food will not kill your metabolism and make you gain 100 pounds overnight as seems to be commonly believed. Your body doesn’t start adjusting how it handles your dietary intake until roughly 72hrs goes by without any…though it will increase production of certain hormones to compensate. This is actually the cycle our bodies are most naturally attuned to. It’s only in recent history that the average person has a refrigerator full of food they can turn to when bored, thirsty, irritated, happy, or any other of a hundred emotional and physical cues we misinterpret as hunger. It takes substantial periods of little to no caloric intake to put your body into true starvation mode, where your metabolism is truly impacted and needs real recovery time.

  • Judy

    I am 68 y/o, 5’3 and had weighed in the mid-120’s range for the last fifty years. Married with three children, my lifestyle is relatively sedentary. Eating three squares and two snacks or six little meals a day does not work for me. I was a semi-faster all my life but was taught I had to eat something everyday. It was only after I read about fasting that I learned my natural fasting tendencies were quite healthy – I decided to eat only when I felt like it and only until I was full. I pretty much eat only the nutrient-rich foods mentioned in the article – with the exception of grains, which I eat very, very sparingly. For the last year, I eat a big meal in the late morning and maybe some fruit or nuts at night – I rarely eat after 3 PM and now weigh about 115.

    Go to the gym for the great cardio and body toning benefits – from what I’ve seen, it rarely results in weight loss – most of the clientele there are bigger than me, My overweight friends who work out regularly get so voracious that they end up eating more calories than they expended at the gym. LOL – I even stopped going to Zumba classes because I didn’t want to get as chunky as the instructors – strenuous exercising only made me hungrier, too. Walking is the perfect exercise for me.

    • ron6788

      You have some pretty strict eating habits and, sometimes, that’s what it takes. When we get older, it gets much harder to stay trim. Glad it’s working for you!

  • Valmr2

    Good to see a positive article on fasting. It’s been around thousands of years. I also will say that it does NOT cause eating disorders. Eating disorders like anorexia are a psychological disorder of body image and to quote Dr. Jason Fung.. “Fasting does not lead to anorexia any more than washing your hands leads to obsessive compulsive disorder. But these lies persist.”

    • Debbie Cusick

      Great to see someone quoting my hero Dr. Jason Fung! IF is the best thing that has ever happened to me in recent years. I have been maintaining a 100-pound weight loss for 6 years now, but really need to lose more weight which is not coming off

  • Paula OConnor

    I’ve been doing 5:2 for a while and LOVE it! If you’re not totally fasting for days and/or binge-eating on the regular eating days, I see absolutely nothing wrong or unhealthy about it. In my opinion, the up/down aspect keeps your body “on it’s toes” if you will & helps with your metabolism. My only wish for My Fitness Pal is that they’d allow you to enter fast days without telling you that you’re not eating enough when you try to complete it. Other than that, I love this article!

    • Lori Zappala

      right? I would love that you could say it was a 5:2 fast day.

  • Judi Hisam Bryant

    From what I have read and also experienced over the years, the best way to lose weight and remain healthy is to adjust calorie intake daily,;to keep blood sugar up the best way is to eat small meals during the day and get daily exercise. Anything under 1000 calories is putting you in starvation mode and is not healthy.

    • JofJLTNCB6

      Every time someone uses the phrase “starvation mode” incorrectly, a puppy dies.

      Why do you hate puppies???

      • Judi Hisam Bryant

        We learned this phrase in Nutrition class.

        • Chris Collins

          I learned the phrase “imaginary numbers” in Trig class…still have no clue what they actually are nor how they function in math problem.

    • Judy

      ‘Anything under 1000 calories is putting you in starvation mode and is not healthy’ … I beg to differ – I’m 5’3 and maintain my 115 lbs by averaging 1K calories a day within a week, which I adjust by fasting. I am by no means underweight. If I averaged 1200-1500 calories a day, I would weigh in the 120’s. It’s what you eat that counts … My 1K calories consist of nutrient-rich, whole foods. Not healthy would be eating 1K calories in empty calorie junk foods!

  • Jessica Kasten

    I think it’s interesting that they say their review was based on 16 total studies, but only cite 3 of them…Hmm…

    • Da Big Shoe

      If you are waiting/relying on study results or science to figure this stuff out, I’m afraid you are in for a really big disappointment. While basic human biology across the planet appears to be the same, we as individuals are just that.
      The best health/diet advice is it stick with real food when hungry (no bar-codes, no spreadsheets, no fitness apps or gadgets), and avoid the 600,000+ ‘food products’, and the associated 100,000+ chemicals.

      • Jessica Kasten

        I’ve read the studies that are out there for this. I was simply stating that they mention they were reviewing 16 studies yet only cited 3. I have tried intermittent fasting myself and am on my 4th month and have seen significant improvements in my bodyfat and overall health. I’ve experienced the benefits of IF anecdotally not only within myself but with a large amount of people (Clients and friends). Studies also show that IF offers benefits of neuroprotection Compared to calorie resitriction alone. I think intermittent fasting is a great way to improve health in many individuals.

        • Da Big Shoe

          That’s great, Jessica! I am sincerely happy that you have found success using IF; it has certainly been a contributing factor in my journey, having lost half my body weight (210+ lbs & counting).
          I read a lot of these posts where folks are struggling with the science, when the only way to know what works for you is to just do it.

    • Anna dee

      Jessica, she stated that the review by Varady (2011) looked at 16 studies, and the author cited Varady. There was no need to cite them again, the other 2 references cited are not part of the 16 studies reviewed. If you really wanted to see all of those studies, you can then look at the journal article by Varady to find them.

  • bigsister86

    I have tried all sorts of diets (Atkins, etc.) but IF is definitely the most effective for me in terms of longevity. I get to feel FULL at least a few days a week. The days after I eat plenty I’m really not that hungry so it’s not hard to fast. I just have to have that very full feeling every once in a while, or I will slip up. Small meals throughout the day just don’t cut it. I’m always starving that way and I feel like my tiny snack just feels like a tease.

  • Lori Zappala

    Sadly some of the people think calories in and claories out is what it boils down to. My doctor confirms that it is just not true. At least not for all people. Nothing ever worked for me btu I tell you intermittent fasting has been a Godsend for me. I totally have lost weight and totally feel like there is hope for me.

    • patstar5

      Well it depends what you put in. If you eat carbs, your blood sugar spikes and your body stores excess energy as fat.
      If you eat fat with low carbs, then blood glucose doesn’t spike and your body burns fat.

      • ron6788

        It’s just the opposite. Fat consumption leads to fat storage. Carbs are burned for energy.

        • patstar5

          Sure! I’ve been eating a high fat and low carb diet for 4 months now and have lost 40 lbs, 60lbs total!
          My body is burning the fat off.

          • ron6788

            I’m glad something’s working for you, keep at it.

            A body needs the nutrition supplied by fruits, veg, and grains (all carbs). Occasonal unsaturated fat, like veg oil, is ok but saturated fats like, cheese, meat, and grease are enemies of the body!

            Generally speaking, in exercise, fat is a slow-burning energy source, a very poor source, although there is plenty of it in the body. Carbs are more easily converted to sugar and burned for quick energy.

          • patstar5

            I’m down 70lbs now. You do not need to eat carbs to live! That is the only macro nutrient you can eliminate and live your whole life without.
            Humans should have never started eating grains (the seeds of wild grasses). Do you eat the seeds of the grass on your lawn? No. Then why would you eat corn, wheat, barley, oats, rice, etc.
            Grains cause so many autoimmunity disorders and grains and sugar are a recipe for obesity and diabetes.
            Humans evolved eating primarily fat and protein, not many carbs and definitely not grains. Grains have only been in our diet for 10,000 years while humans have been here over 1 million years.
            Fat has more energy per gram than protein and carbs combined. Studies have shown the brain runs better off of ketones than glucose. It is true that our body needs some glucose to live but that can be obtained through gluconeogenesis where our body turns protein into glucose.
            Our glycogen stores only last us 2-3 days and only hours in intense workouts, fat stores are much more reliable. Humans did not evolve eating carbs on a 24/7 basis, there’s no reason why we should be doing it

  • jal333

    Wish that myfitnesspal was designed to better support 5:2 fasting.

  • DailyDose

    Yet another article with no conclusive opinion. The headline asks a question and at the end of the article… I’m still asking the question with no answers.

  • MCP

    Those that say this is unhealthy need to look in the mirror. If you have an issue with eating/not eating you will experience problems on any diet. As some here have mentioned there is a larger internal issue that needs to be addressed. It is nice to see MFP broaden their concepts of what ALL people may be doing. Specially love how some are trying to come down on MFP for posting something different… no one is forcing anyone to do anything.

    As for the comments on Muslims fasting for 1500 years and Jewish fasting for 5000… man prior to civilization were fasting long before, albeit mostly to the credit of nature. Think about how our ancestors would have eaten throughout history. I challenge you to find some with the capability to eat 3 meals a day with snacks in between. It just was not feasible in until the most recent few hundred years.

    Personally I am 35 and have the slowest metabolism in existence. I have tried many different diets with varied levels of success. As to when fasting, I could take in zero calories for 24 hours and would lose 1 pound.

    Bottom line is EVERYONE is different and should not speak against other options simply because they FEEL its not healthy. Good luck in your endevors.

  • patstar5

    Some days I just try togo 12-24 hours without eating, I haven’t really been hungry anymore after going low carb. I only eat once or twice a day.

  • Mohan

    Imagine the benefit to the world if we stopped “slaughtering” other beings-
    And fat americans should starve anyway, and become vegans.
    There will be a great economic impact in less food wasted that even the fat americans cannot finish off their plates, and fat baastards won’t take up 2 seats on a plane, with their rolls of flesh around their waist.
    It will definitely be a more humane place if people ate for living instead of living to eat. They are just large protoplasmic retards that have affected the planet’s other beings.

    • ron6788

      You need to lighten up. I’m sure you have your own faults. Fat people pay. If they use two seats, they will pay for two. And they’ll pay plenty at the grocers and plenty in insurance and health-related issues but that’s their choice. Doesn’t need nasty side comments from you.

  • khalid a

    I’ve been doing this for more than 5 years
    5 days I workout 1.5 to 2 hours/day and eat Whatever I want and 2 days No exercises but I fast 12 – 15 hours/day
    The days I am fasting I don’t feel sluggish

    • Stephen

      Water fasting was a real miracle for me. The time to start, is in the morning, after you have gone without food all night. I have type 2 diabetes, high blood pressure and the Doctor said my kidneys were working only 25%!!! That hit me like a bombshell. My legs and ankles began to swell real bad, and I couldn’t get them to go down, even with water pills and etc. I was desperate, and went on a three day water only fast….The results…my sugar went down to normal, high blood pressure went down, and best of all…the swelling in my legs and ankles went down to normal!!! Thank the Lord!! My next option would have been dialysis. I can say that water fasting really works, as I lost 10# in three days and went off all of my prescription medicine!! The secret is to start in the morning and to sip water through out the day. I went for another 3 day fast, the next month, and have kept the 20 lbs almost entirely off. It was a life saver…try it and see. Be sure only to take water.

  • JoanA

    There is a contingency for maintaining your weight. It’s called 6:1.

    • ughughughugh

      That’s still not eating normally. And again, let’s hear from folks who’ve been doing it for five years or more.

  • Serena Tsang

    I will say that for some individuals, it is too easy to abuse fasting (which is really just a tool) and slide into an eating disorder. I am not saying that fasting itself will give you an eating disorder, but to anyone who has/had/is recovering from an eating disorder, do be careful about IF. Make sure you have a healthy relationship with food first, and also have someone monitor you in case you do start showing disordered behavior/thinking.

  • Victoria Skelly-Buck

    I love IF. Sorry some of you do not and some of you think its an eating disorder. Mind boggling really… I eat from 1-9 pm every day. I eat very healthy. IIFYM carbs/fats/protein. If I know I have an event coming up, the day before I may go lighter on calories. But this is how I would eat if I were NOT Intermittent fasting. I am not hungry until 1pm (ish) and so it works. I don’t crave certain foods or go on binges… that is a certain mindset of someone with a disorder. I don’t look at food as a reward for starving myself. Because I am not starving. I’m eating as I normally would but within a window. People need to check their facts before spouting off.