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Does Intermittent Fasting Work? 4 Myths Busted by Science

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Does Intermittent Fasting Work? 4 Myths Busted by Science

Intermittent fasting is all the rage these days, but does it work? Is it better than traditional dieting? Let’s find out…

 

Are you eager to lose fat and gain muscle with less work?

You know that you need to eat fewer calories than you burn to lose fat. You also probably know that intermittent fasting can be an easy way to help you eat less.

However, you might be confused. Some people say intermittent fasting will make fat loss almost effortless. Others claim that intermittent fasting will make you lose muscle, and may even be dangerous.

If you read up on intermittent fasting, you can quickly learn that the major claims both for and against it are dubious at best, but in this article, I’d like to address a few myths that aren’t commonly addressed.

Myth #1:
Intermittent fasting will help you lose fat without a calorie deficit

When you go without food long enough, your body starts burning fat. Fasting also increases your insulin sensitivity, which generally helps you store less fat.

Theoretically, you could lose fat by fasting around 12-24 hours, and then gain muscle when you do eat. Some people have also claimed that intermittent fasting “optimizes” or “balances” your hormones in a way that helps you store less fat and build more muscle.

The problem with this idea is that your total calorie intake evens out over the course of a day. If you burn 50 grams of body fat during a 16 hour fast, you’ll gain it back if you eat enough calories to maintain your body weight during the other 8 hours.

There’s also no evidence that intermittent fasting will change your insulin levels enough to affect your body composition. 

In one study, people did lose fat after they switched to one meal per day instead of three meals per day. However, the differences were very small, and they weren’t exercising or closely monitoring their calorie intake. The study also used BIA to measure their body fat levels, which is notoriously inaccurate.

The bottom line is there’s no strong evidence that intermittent fasting will help you lose fat without also eating fewer calories than you burn. 

Myth #2:
Intermittent fasting will help you lose fat and gain muscle at the same time

This idea is similar to the first, yet takes the concept one step further. Like the first myth, there’s almost no evidence this is true.

A study commonly offered as proof that intermittent fasting does help you lose fat and build muscle simultaneously is a small review in 2011 that found that, on average, people who used alternate day fasting lost less muscle mass than those who cut calories every day.

The problem is the studies reviewed all used slightly different designs, which means the results could (and probably were), due to chance.

If you’re a complete beginner, you can lose fat and gain muscle at the same time. Otherwise, you’re better off focusing on one or the other

Myth #3:
Intermittent fasting is better than snacking throughout the day

For a while, almost everyone recommended that you eat small meals throughout the day. Self-styled gurus everywhere claimed that it helped keep your blood sugar and hunger under control, boosted your metabolic rate, and provided more energy for your workouts.

Well, we now know that these ideas are false and the “guru pendulum” has swung in the other direction: many are now saying that eating many small meals throughout the day is actually bad for you, or at least not as good as eating fewer, larger meals.

There is some evidence that eating more than 3-4 meals per day doesn’t keep you as satisfied as limiting intake to a few meals per day. However, if that applies to you, you don’t need to be intermittent fasting to eat fewer, larger meals.

On the other hand, you can find studies wherein participants were less satiated on 3 meals per day, and found that increasing meal frequency increased feelings of fullness and made it easier to stick to their diets. And again, you can do this with or without following the intermittent fasting protocol.

You may have also heard that eating small meals will make it harder to lose fat because you’re keeping insulin levels higher throughout the day. Well, as you learned a moment ago, however, insulin levels average out over the course of the day, and worrying about small fluctuations is pointless. When you eat a large meal, your insulin levels will stay higher for longer, resulting in almost the same effect as snacking.

When we look at the research, the reasonable conclusion is if “grazing” throughout the day helps you stay lean and satisfied, then do it.  There’s no evidence you’ll get better results with intermittent fasting.

Want a workout program and flexible diet plan that will help you build muscle and get strong? Download my free no-BS “crash course” now and learn exactly how to build the body of your dreams.

Myth #4:
Intermittent fasting is bad for women

 

 

 

 

 

 

 

 

 

There is some evidence that women don’t respond as well to fasting as men.

One study found that alternate day fasting actually decreased women’s glucose tolerance, or how well they process sugar. Another study on women found that intermittent calorie restriction, which is similar to intermittent fasting, made them hungrier and less likely to continue dieting.

However, there’s little evidence that it’s dangerous, or worse for women than a normal meal schedule.

Other studies have shown that alternate day fasting or calorie restriction works extremely well for women. Even in the previous study where women felt hungrier and less happy with alternate day calorie restriction, they still lost slightly more weight than those who stuck to a daily calorie deficit.

If you’re a woman, there’s almost no scientific evidence that intermittent fasting is bad for you, or not as good as eating more often.  That said, like with men, intermittent fasting doesn’t possess any particularly special properties for you, so you aren’t missing much if you don’t like it.

Intermittent Fasting Isn’t Particularly Special or Bad

Most evidence shows that when you eat isn’t that important.

If intermittent fasting helps you eat less or gain more control over your diet, then do it. If you like to eat more frequently, that’s fine, too. 

Having a plan that you can stick to, that allows you to hit your calorie and macronutrient goals, is what will give you the body you want. Don’t worry as much about when you eat.

What do you think about intermittent fasting? Have anything else to share? Let me know in the comments below!

armilegge Armistead Legge is the Director of Content for Muscle for Life and Legion Athletics. He has completed over 100 triathlons and cross-country, cycling, and adventure races, and has researched and written for over a dozen organizations, including the National Institutes of Health. When he isn't helping people get into the best shape of their lives, he's lifting weights, riding his bike, hiking, camping, reading, and making delicious food.

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  • Vase

    I agree that it depends on the person. I am not hungry at all in the morning, and work out early, so it works for me to have my first meal in the afternoon. My wife, on the other hand, has to eat in the morning or she will have a miserable day. You just have to find what works for you. Just don’t forget those bcaa if you are fasting, to avoid catabolism.

    • Hey Vase, I agree completely. It’s largely individual. Glad you’ve found something that works for you.

    • Chad

      “Going catabolic” is as big of a myth than the ones outlined in this article. The only way a person will go catabolic is if they literally starve for days wothout food.

  • HYNK

    Good article. If you want to do an article on cracking the high intensity cardiovascular is bad for IF myth; in that you’ll lose muscle mass, contact me. You can see I do a ton of cycling and endurance training. http://www.myfitnesspal.com/BlakeHorton

    • Thanks man! I also agree with your statement, it’s certainly possible to gain or maintain muscle while doing HIIT.

  • Pingback: Does Intermittent Fasting Work? 4 Myths Busted by Science | A.D.A.M.()

  • flyjohny

    I am fasting for a couple of months now, and it works fine for me (I feel some hunger in the morning, but it’s much easier to control the cal. intake and macros) but I need to increase calories now because I hit weight plateau. It is difficult for me to eat more during my evening meals (so much rice!) so I was recently wondering what could happen if I would add another mean before my current first meal which is around 1PM. This article perfectly addresses my doubts 🙂 Thanks!

    • Hey man, good question. It sounds like you’re trying to gain weight. If that’s the case, you’re going to need to eat more as you said.

      If intermittent fasting is making that difficult or uncomfortable, then it’s fine to add another meal outside of the fasting window. The benefits of the extra calories are far more important than sticking to a certain feeding window.

  • Murilo

    I’ve been “oficially” IF-ing now for over 4 months now and I wrote “officially” because I’ve IF-ed for years without knowing simply because I never had a big appetite in the morning, so I would just wake up, have a shower and leave to work, while having my first meal at lunch time only…

    That said, I was very skinny then because I was not training and not hitting the right macros, but once I started doing it, things have changed… I never lift as much weight as I’m able now…

    When I started lifting, I did do the 7/8 meals a day as it is preached in the mainstream, but looking back now I can see that I was miserable by then.
    I was constantly hungry, eating non stop and I would get very, very grumpy if I could not eat (I feel sorry for my fiancee haha)…

    I still get funny looks when I tell people that I haven’t had breakfast in months, but I don’t care and I can say that IF works for me…

    I definitely recommend people to give it a try once and see how they feel, but of course, ensuring that their macros and workout plans are correct, otherwise there is no point and they will end up blaming IF for their lack of progress…

    Cheers
    M

  • Good article. I’ve doing some form of 16/8 about a year now (sometimes 14 hour fasts, other times 18, and for a time I did a 24 hour fast once a week) and I like it. I feel “on” pretty much all day, though I do get a bit tired after my first meal (usually around two or three).

    I’m not really that interested in the fat loss side of IF. What got me interested is the idea of autophagy (basically that the body “eats itself”) which is supposed to help your body “clean house”, so to speak. Would like to hear your thoughts on that.

    LC

    • Michael Matthews

      Thanks! Cool on what you’re doing.

      Yeah there is plenty of good evidence of IF’s benefits regarding autophagy and thus longevity and immunity.

    • nickjaa

      damn good point and it almost looks like that’s the most important aspect of IF

  • Caino Papettas

    It leads to serious eating disorders and poor relationships with food like obsessive eating, its just another stresser in life that we dont need

    • Michael Matthews

      It CAN, but some people do really well with IF.

      • Yeah and I’d like to disagree with those eating disorders as IF will actually help with those.

        Before IF I was highly addicted to sugar (it has been scientifically proven to be 8 times more addictive btw) so I had really hard time not to snack with something high in sugar.

        So obviously I thought that after all of my fasts I would be a sugar eating maniac?

        Nope. I didn’t I actually don’t even need sugar anymore and I’m consuming it far far less than I did before starting this whole IF thing

        Btw I’m doing 24 hour fasts at the moment and the things are even better now.

        • Michael Matthews

          Awesome, glad to hear you’re doing well!

    • Tom

      Hey, look, a comment with no factual basis.

  • Laura

    Been IFing 16:8 for the last couple of weeks, breaking my fast between 12 and 1pm. What’s interesting to me is that I actually don’t feel hungry in the afternoons at all. Previously I would eat breakfast at around 7.30/8am and NEED to eat every 2-3hours. Now I can easily last from my first meal at 12/1pm until 4 when I have a protein rich snack, and then dinner at 6/7pm. I’m not craving sugar any more, like IF has switched off something!! Is this common?!

    • Michael Matthews

      Yup I’ve experienced that before. In fact, I don’t get hungry anymore period no matter how long I go without food. It’s strange.

    • Tom

      Yes, it is. it’s very common for people to report fewer sugar cravings as their body “remembers” how to burn fat stores for fuel.

  • TOG

    Great article as usual. I’ve been “out of the scene” for many years but, have just jumped back in due to the motivation this community offers. Back when I was considering competing I did a type of IF as well but, purely on accident as I just could not stomach breakfast. I was usually able to maintain lower bf’s but growth was definitely stymied as I found myself unable to get enough calories in during the rest of the day. Its a give and take with IF, as now known, and everyone is different. I know for me, I feel better when I am hungry! For some reason when I am full I feel like crap though you wouldnt know it by the pounds ive packed on this year. This brings me to a question…..If completing the one year challenge and already getting my meal plan am I better off sticking with the meal plan or adopting an IF tyoe schedule to trim fat? Fat reduction is currently my main goal and I am willing to cannibal a bit of muscle to do it.

    • Michael Matthews

      Thanks!

      Yeah bulking on IF is pretty awful. I don’t think anyone likes eating 1k+ cals every meal.

      If you like a traditional style of eating stick with it. IF won’t do anything special in terms of fat loss.

  • Thanks for stopping by and checking out my article! I hope you enjoyed it.

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  • alex

    What’s your current eating window?

    • I IF on the weekends just because I like jamming my lower calories into fewer meals. Mon – Fri (training days) I eat on a traditional schedule.

  • alex

    I honestly believe that to keep an IF lifestyle, people should just do ONE simple thing: Learn to skip breakfast! You’re almost always going to eat lunch and dinner with friends/family/co-workers. If you just skip breakfast and have an early dinner (6pm-8pm) you’ll have no problem living this lifestyle. I eat at 12pm and then just have dinner anytime I want before 830pm. However, if there’s a special occasion, I might eat a little later on a particular day but this does not hurt you! You’ll still get a good 12-14 hours of fasting if you just skip breakfast even if you eat a littler later. That’s it people, discipline yourself to skip breakfast and drink ONLY black coffee or water during your fast.

  • Jenny Hudson

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  • NSW

    It’s very hard to determine whether, given the same number of calories, IF results in a significantly greater fat mass loss. However, in my experience (I’ve been eating within approximately a 5-6 hour window for about three years now), the real benefits are a) a nearly complete absence of hunger (which you have noted); b) on a related issue, no low blood sugar related performance lows; c) very nice blood lipids (I primarily track triglycerides and to a lesser extent, HDL/LDL ratios); and d) the possibility of enhanced neuronal autophagy (which feels more relevant as I approach 51 years of age). But I think your article is balanced, and I believe that a certain M. Berkhan might even agree with most or all of your points!

    • Thanks for the comment and I agree on all points. Keep up the good work.

    • EJ

      ‘The possibility of enhanced neuronal autophagy” In your opinion, does this explain the mental clarity boost doing some form of IF consistently?

      • That’s possible, although exercise also has some similar benefits. There isn’t much evidence at this point to say one way or another.

  • victor

    I have two points…
    1. Many people say that they practice intermittent fasting, while their eating window starts at 1pm and ends at 9pm. I would not even consider it ‘fasting’. They are just skipping breakfast, no big deal at all, nothing much to talk about. They are saying “I fast for 14 hours” – seriously? I don’t know anyone who eats at night regularly, so why are they counting the 7-8 sleep hours as part of their “fasting” hours? Their fasting really begins when they wake up, so an average, they “fast” from 7am to 1pm – wow – 6 hours!!! I regularly eat at 4pm after the gym (I workout during my late lunch break), or quite often my first meal is at 8:30pm at home. My workouts are quite intense and after a few days of getting used to fasted workouts – I actually feel more energy and have increased my push-ups and pull-ups significantly. Now this might be considered intermittent fasting, but in my book – only if you skip the entire day of food (night+day+night) – that’s intermittent fasting. I’ve done a few 14 and 15 day water-only fasts, for the record… People make such a big deal of eating regular meals 3-4 times per day… Read up on water fasting (Herbert Shelton and others) – you’ll see that 100 years ago it was perfectly normal to have 2 meals per day and some time earlier – it was normal to have one meal per day.

    2. HGH. Human Growth Hormone. Not mentioned here at all. For those who workout and want to grow muscles or increase strength – look into ‘fasted workouts’. HGH level increase if you workout on an empty stomach. I don’t like to workout in the morning, plus I feel like my fasted state is more pronounced after 12pm, so I workout some time between 1 and 3pm, then have a small meal at my desk or nothing at all until I get home.

    • Well, technically fasting begins when the body enters a fasted state, which is going to be anywhere from 3 to 6+ hours after you ate your previous meal.

      You’re definitely right that meal frequency really doesn’t matter. Having protein before and after training probably helps slightly over the long term but it isn’t a game changer.

      Slight fluctuations in HGH aren’t going to make any real difference. It just sounds good. 🙂

      • Paul

        Mike,
        Tell me why they’ve done studies in mice and the If group lived almost twice as long as the regular diet control group… also they have done studies where they induced alzheimers disease in mice and they had one group do IF and the other traditional diet… the ones on IF lived on average about 30 (human years) longer. Its been proven to help you live longer… during the Great depression, they have shown that the life span average increased instead of decreased… so less food equals longer life… its all there for you to see…

        • Remember we humans aren’t just big mice and don’t mix up correlation and causation.

          Now, there’s no question that good things happen in the body when you’re in a fasted state (especially immune-related things). That’s well established. It’s a stretch, though, to say that IF is going to help you live significantly longer.

    • Tom

      You count the sleeping hours because of basal metabolism. I fast for 20 hours every day. My brain and the rest of my body continuously requires energy, whether I’m asleep or not. The brain alone burns through around 400 calories per day. If you aren’t eating regularly, your body has to pull that energy from somewhere or you would go into a coma and die. When you eat normally, the body’s “battery,” the liver, maintains a store of glycogen which it can convert into glucose. When you do IF, your glycogen store is always depleted. Hence weight loss. I guess if someone was drinking soda every day or w/e they won’t lose weight, but I don’t think we can call that intermittent fasting.

  • Gile

    Just like everything else out there, not one thing works well for everyone, but may work one for some. I personally had been stuck at weight loss plateau for more than a month and in just two weeks of following the 16/8 Leanfast program I have already lost another 10 lbs. Here’s an interesting article with a little more actual research on IF.
    http://www.leangains.com/2016/03/intermittent-fasting-where-are-we-now_18.html

    • I completely agree. If you enjoy doing IF and you get results with it, go ahead. If not, don’t.

      Great to hear on the results you got using IF.

      Thanks for sharing the article. 🙂

  • Bob

    Hey Mike, I’ve been following your BLS (cutting)/BBLS (bulking) programs over the last 15 months as well as following a 16/8 IF eating schedule. I started at 255lbs around 30% bf and now I am 202lbs around 9-10% bf. I love the IF eating schedule because it allows me to keep my calories down while still eating a big lunch and dinner. I have no hunger issues in the morning before eating my first meal. It is tough to follow when bulking as eating 3500-4000 calories in 8 hours is difficult. Anyway, thanks for all the information you have put out! I didn’t think I would ever be as lean as I am now until I found you website.

    • Hey Bob! Cool you’ve been rolling on BLS and BBLS for the last 15 months!

      Awesome job on the results, and cool you’re doing IF!

      My pleasure! Happy to have helped. 🙂

    • EJ

      16:8 requires 7 days of IF, correct? What do you think would have happened to your result if you dropped to 3 days a week doing 16:8? That type of IF has been working really well for me. I’m not sure if the additional gains from 4 more days is worth it. I have to say that my muscle definition, weight, moods, and mental clarity has improved doing IF for just three days + Wim Hof breathing.

  • Steve Goguen

    I love eating all my calories in a smaller window. Never any issues with satiety. Don’t think it helps any more with fat loss. However is it a good anti-aging tool? I was originally down to the idea because supposedly the fasting period slows down aging via autophagy.

    • There’s evidence of this yes but a much more powerful anti-aging strategy is just regular exercise.

  • Ifi

    Hi all. I like the idea of IF, but I don’t think anyone can say that the body will burn fat while fasting and no muscle at all in these 16 hours. In a fasted state, its more logical that the body will burn a combination of fat and muscle. There is not a timer and switch in our body. Also, while most users in comments and forums say that IF works for them, we don’t know their initial state. If someone just started, or was not ever in an advanced level (like Michael) its normal to assume that IF helps him lose more fat. But he can’t see how much muscle he is losing.

    • Thanks for the comment.

      If you do it right, the muscle loss while fasting is negligible.

  • Andrew Bayon

    Hey Michael I was curious about one think about the Fasted and Fed State, I’m sure you heard of adding Grass fed butter and coconut oil in your coffee. The reason I do it is a healthy form and quantity of daily fat intake. So it cuts the amount of fat needed the rest of the day, and it promotes weight loss. What I’m curious about is if the butter and coconut oil will end up ending the fasted state?

    • Hey Andrew! I talk all about this here:

      http://www.muscleforlife.com/butter-in-coffee/

      To answer your question on the coffee and fasting though, the amount of fat that’s in it would break the fast.

      • Andrew Bayon

        Awesome Article ! And I appreciate it, I began to think that it was after researching the fasted and fed state.

  • Tom

    There’s so much wrong in this post I don’t know where to start. You need to study up on basal metabolism.IF ensures a calorie deficit unless you’re trying to burst your stomach each day. You burn through your glycogen store very quickly. Plus, after the first few days, most people who try IF report eating a lot less than they thought they would. Sugar cravings subside, etc.

    • Wut?

      IF does not guarantee a deficit. What are you talking about?

      This might help you:

      http://www.muscleforlife.com/bmr-calculator/

      • Michael Huser

        I agree with Tom this article is not accurate, I did the whole eat 4-6 times a day and had my macros in check. I even weighed my food out. I worked out almost 2hrs a day M-F even some Saturday. Im 247lbs 5′ 2″ 25 yrs old. After 2 months I lost 8lbs and for another 2 months I stayed around 240-238 even tried lowing my calories from 1800 to 1200 for 2 weeks and nothing. I had a blood test and all was good the doc said.

        I got alot of info from YouTube about intermittent fasting and after trying it for 1 month, eating the same foods (1800 calories) I dropped 12lbs. Now 2 months later I’m 201lbs and I’m acual lean lookig and cut.
        From size 42 to 34 pants
        XXL shirt to L
        I’v been fat my while life and I’v done all kind of diets with no results. I fast for 16hrs and eat for 8 2pm to 10pm
        3 meals
        I’v never been in this good of shape. If you want to lose weight fasting is the way to go. You can find more credible info from doctors on YouTube that will explain why and how it works. You still need to eat healthy, but you will see results. I eat protein 160g , 100-150 carbs, 70g good fats. And have a skinny cow ice cream every night hell yeah!

        • Glad to hear you’re doing well Mike.

          I’d bet dollars to doughnuts that you were making one or more of these mistakes with the traditional diet, though:

          http://www.muscleforlife.com/not-losing-weight/

          • Albert

            Regular dieting is trash!!! IF IS THE BEST!!! have done traditional with good results. But it is just a pain in the ass meal prepping and eating out of plastic containers all day. Now I eat fresh every day. 2 meals a day. Fast for 18 hours and have way better results than traditional. Not to mention the energy increase and IF makes u drink more water. Also another benefit

          • Cool. Whatever works for you man. At the end of the day, it’s all about being in a negative energy balance, so it looks like you were accidentally eating fewer cals than when you were meal prepping–hence the better results.

  • John

    IF works for me but only if combined with at least light regular exercise and cutting out empty carbs as well. Unfortunately though, you will gain the weight back gradually if you fall back on your old habits such as drinking or snacking late at night. I almost never eat breakfast regardless of IF.

    • Thanks for sharing John. At the end of the day it’s all about creating a negative energy balance if you want to lose weight.

      • VainSaints

        No. It’s not. It has nothing to do with ‘creating’ an energy balance. This has been proven wrong long ago.

        You don’t create an energy balance because the body regulates energy output better than you can regulate “energy” input. Exercise, unless exceptionally strenuous, can only account for a small fraction of the energy consumed by the body’s natural metabolic processes. By trying to keep an “energy balance” you are fighting an uphill battle against your body. You have to outrun your diet, then outrun a lower body temperature, then outrun lower blood pressure, brain function, sluggishness, etc. The body adjusts its internal processes to match the caloric input so long as insulin levels are signalling that calories are coming from an external source.

        Please stop peddling false information and then falling back on “Whatever works for you” cop outs when you hear reports of people losing weight efficiently on fasting protocols.

        There is a reason why all the commenters, even those much more friendly than I, who report gains claim that they achieved them on a fasting protocol rather than a calorie deficit strategy. There is a reason why virtually no one here has issued a comment praising how effective their calories in- calories our approach was. That is because it is ineffective. The calories in-calories out approach is doomed to failure.

        • Do you have any evidence you can reference to support the idea that creating a calorie deficit isn’t necessary for fat loss? I covered that topic pretty extensively here: https://www.muscleforlife.com/healthy-meal-planning-tips/

          I’ve also never fallen back on the “whatever works for you” when it comes to energy balance. It works for everyone, and that’s what every controlled study has also found. If you’ve found something that proves otherwise, I’d love to see it.

  • Inês Dionísio

    I have started IF a weak ago and I am having double feelings. On one hand I have not lost anything at all. I am not really worried about if for now because that is how my body tends to react before gaining speed (it holds on to everything! ). On the other hand, I am happy with the fact that the bloating sensation is gone, gallbladder pain is gone, being able to experience my body movement better (that was a surprise), sleeping better and learning here that helps with aging process! I am also happy that it doesn’t cost me money, time and it takes my mind of food, it has helped me with self-control (although some say “everything or nothing is not self control!). It has also helped with fear of feeling hungry. .. I can go hungry and nothing bad happens!
    I do notice that on eating intervals I cannot eat so much, and that’s good. I am starting to think that if I can stay doing this long enough, I might finally start thinking like a slim/healthy person! Although if I don’t loose any weight it is going to be frustrating and all the good things about Intermitent Fasting will not “overweight ” 🙂 that frustration.
    Cheers!

    • Hey that’s great, Ines! Glad you’re experiencing greater overall well-being after starting IF. Keep in mind, it’s not the weight loss magic bullet. It will still come down to keeping a negative energy balance consistently over time. Sounds like IF is helping you get some great habits down. 🙂

  • Sandva

    I am a female over 60 who has been int fasting for 8 months now. I have lost 20 lbs and am holding my weight at 109. I fast 2 consecutive days a week restricting myself to 500-650 calories a day on fast days. The other days I eat normally at approximately 1500-1800 each day. I try to walk on all days. This program works extremelly well for me. I feel great coming off the 2 day fast and am delighted to have found a method of weight control that works for me. What a pleasure to semi fast 2 days a week and eat normally the rest of the time. I never successfully dieted any other plan in my life. San

    • That’s great, San! Good to see IF working out for you in creating a sustainable deficit in your diet for you to lose weight. Nice job!

  • Karla

    I’ve experimented with IF. So far, the best thing about it, for me, is it’s trained me not to go into panic mode when I’m hungry. The biggest downfall for me in dieting is sticking to a schedule, and then, in hangry panic mode, eating something quick, convenient, and too often not on my diet plan. I spend most of my days alternating between work, running errands, and taking kids to their activities, driving all over the valley. I can’t always keep my food in the car with me (I’ve tried, it’s gross). Learning to identify true hunger, then calmly reminding myself I won’t starve to death if I don’t eat in the next few hours… Well, it’s helped a lot 🙂

    • That’s great, Karla! Sounds like it’s a system that works for you to create that daily deficit. Nice!

      Also, food left in a warm car is definitely gross…

  • AK

    Arnold (terminator) used to over-eat one week then under-eat the following week….then repeat.

  • AK

    I tried fasting (eating a large meal every 12 hours). Noticed feeling high blood pressure and constipated. Did not reduce belly. And my arms and legs shrunk. I did have slightly more energy & alertness midday.

    I’ve learned it’s not when you eat, it’s what you eat that matters. Anyway, going back to Weider principles of eating at least 3 meals/day.

    • Cool! Sounds like you’ll do better spreading out your meals. And, you’re right. It’s not so much about the when as it is about the what.

      • Brian badonde

        But when you eat is completely relevant, your body isn’t just hanging in digestion 24/7. My feeding window is ~7-9pm and I feel my very best between 12-18 hours fasting. I don’t think a big meal every 12 h is very helpful if you’re seriously considering IF. Good luck on all of your body endeavours though!!!

    • Ga

      I think where you messed up is the only 1 meal every 12 hours, even if your fasting you still should get your normal calorie intake. Cant retain muscle if your not fueling them with the right foods. I eat smaller meals Fasting, and am turned off by fried foods and sugar but maybe more so because I am planning a healthier meal since i;m so hungry before I get to eat and want to make sure I’m getting enough protein after my workouts. One thing I love it since fasting is quitting soda, which was the hardest thing before this. One other thing I would suggest that works for me, Is I try to drink a tea or juice with low sugar content to give my glucose levels a boost

  • Jason Yap

    i’ve been on IF for a year (leangains) and got much shredded and more muscle definition than before IF which was on a calorie deficit based on 3 meals/day. i do have 1-2 days of break in a week where i eat 3meals/day.
    From my 12 months experience, IF is no magic but it DEFINITELY make calorie deficit much much easier than a 3meal/day regimen. Imagine you have to eat all your calories within a 4/6/8 hours window depending on your IF approach, every meal become so satisfying..I’m still doing it weekly whenever i could..

    • Sounds like it’s working for you! That’s awesome man. Keep at it.

  • Ga

    Good article, doesn’t say it is bad, but doesn’t say its great, and mostly says it depends on you. Most articles I read condemn IF and then create reasons that are unrelated, like one blamed it will start a caffeine addiction?????!!!!! I know since i started IF which I will only eat between the hours of usually 3 to midnight, I actually find myself craving protein rich foods, I do eat a little more carbs then I thought I would and I get sick trying to drink soda and eat sugary foods.

    • Thanks!

      Haha caffeine addiction through IF?

      That’s great IF is working out for you! 🙂

      • Ga

        Yeah it was a huffington post article. They couldn’t get enough bad on IF so they blamed caffeen addiction as one of the 5 negatives.

  • Loren Fok

    Jason Fung a Toronto medical doctor who has treated many patients with type 2 diabetes caused by obesity with IF. He has backed evidence with logical arguments as to why it works. It may seem unconventional, but when you have generations of obese people and no definitive answer as to how to fix it. Sometimes you have to resort to unconventional methods. Check out his website https://intensivedietarymanagement.com/ it has a lot of useful information regarding IF and just healthy nutrition overall.

    • I’m familiar with him and his work and there isn’t anything particularly “magical” about IF and weight loss. It can just help some people be more consistent with their caloric intake.

      • FormerFan1

        Mike, I’ve been on so many diets from “Guru’s” that did nothing. No I didn’t fall off the wagon, I was extremely strict with their instructions which is always primarily about a caloric deficit and yes, you lose weight at the start but it never lasts as your metabolism slows to adjust for the caloric deficit. I’ve upped my calories to “Maintenance” and fasted 16 / 8, low carbs and sugar and guess what, fat is melting off and I’m never hungry cause I stuff my face with good foods.

        Now you could say, well good for you, that’s how your body responded. I just told 5 people how to do it and for the last month they’ve all been losing 1/4 to 1/2 a pound a day, feel more energetic, no brain fog, not tired after meals and love life again. It’s not just certain people, it’s insulin and the effects it has on EVERYONE. Of course there are people more insulin sensitive, but that doesn’t change the fact that insulin IS the cause of fat storage, not number of calories as all calories are not equal.

        Taking in 2000 calories of chicken and good fats have a completely different effect on the body then taking in 2000 calories of chocolate bars and sweets, because sugar and carbs skyrocket insulin which leads to fat storage. You will gain fat on one, and not on the other.

        Done deal, no “guru” can fool me anymore and sell me a miracle anything supplement. Fasting is free and has been practiced for hundreds of thousands of years throughout all cultures.

        I get it though, people have to make a living so telling people to simply fast and stay away from sugar and carbs would destroy a whole industry of supplements that are not needed and snake oil meal plans.

        Whether it was my profession or not, I have a conscience and could not do that to people.

        I hope you see the light.

        • Hey man, glad you’re having an easier time maintaining a weight you’re happy with.

          I think the evidence points to a slightly different interpretation of the role of insulin in weight gain and fat storage, which I wrote about here: https://www.muscleforlife.com/how-insulin-works/

          I’ve also written about the role of sugar (or lack thereof) in weight gain here: https://www.muscleforlife.com/sugar-facts/

          …and how food quality affects weight loss here: https://www.muscleforlife.com/clean-eating-and-weight-loss/

          • VainSaints

            Anything that purports that sugar consumption has nothing to do with weight gain is peddling bro-science that is beyond antiquated, and probably lying.

            The calories-in calories-out lie has been refuted so decisively, so completely and so overwhelmingly that I can’t believe that people exist who still peddle this nonsense. Is this guy pretending that insulin responses don’t matter?? Insulin is what determines what the body will do with the foods it consumes and the food it has stored. The body has no inherent response to calorie intake. If you put 10,000 calories of lard in a bath-tub, the tub will not get fat. Same with sugar and lean chicken. A bathtub has no mechanism by which to convert sugar or fat into anything. The body does have such a mechanism, and it is the mechanism which determines what happens to the inputs in the system, what converts these inputs into PTP, or glycogen, or fat.

            Despite the mostly gaseous handwaving which the “sugar facts” article consists of, there is overwhelming evidence that refined carbohydrates are the primary causitive agents of obesity.

          • Would you care to cite the “overwhelming evidence” you’re referring to?

          • michael ferrel

            The American public should be a good example.

          • Hmm, in what way does the American public refute energy balance?

  • Hollay Ghadery

    One of my health care providers got me onto IF for sleeping problems and thyroid issues. (I gained 30 lbs after my third child with NO changes to my diet, and other than amping up the impact-intensity of my workouts, no changes there. Just baby-hormone BS.)

    In 12 weeks of IF, I lost 20 pounds. Eating the same things, just in a restricted window (9am-5pm). Granted, I don’t and wasn’t eating crap to begin with, but IF seems to have checked my system. AND I don’t IF every day: 3-4 times per week, with days depending on my workout cycle. (Tough to do a 15km run when you haven’t eaten in 16 hours, so it’s usually Power Yoga or a shorter run or HVRT on days I’ve fasted. I also work out first thing in the morning.)

    In any case, it works for me, so I roll with it. Solid article.

    • Awesome, Hollay. Thanks for sharing!

    • Ajim Osman

      excellent comment here Hollay! I do IF 5 days a week. I take breakfast on weekends but clean ones like oat etc. Weight loss is there but nothing to shout at but the real benefit I can see is that added energy I have during my daily workout at 6 am..not sure whats the science behind it though :).

  • EJ

    There’s no mention of the HGH release or doing HIIT workouts while doing IF. This would have been very helpful to read.

  • Ezzat

    Awsome article, im a physiotherapist, and have continually come across the same research. I however do not recommend IF, but I love how your unbiased and continually mention that everyone responds differently. I cannot say i disagree with anything you said. As well i would like to mention, there a possibility for the placebo effect for many seeking these fad diets.

    • If a particular protocol like IF helps you stick to the diet and helps you achieve your goals, that’s what counts. I’m glad you like the article!

  • blake davis

    I feel it worthy mentioning I’ve always struggled with eating a lot of food fast. Growing up I was taught to eat a lot of food fast because you didn’t know how long it would be until your next meal and you did not want to complain saying you were hungry like you were a baby.

    Now combine this with the stress of being an adult and I found myself constant eating all day to make up for the stress. With IF I now can comp my habits in a way that works for me. Instead of constantly eating a lot of food fast all day, I can still eat a lot and fast but in a small time frame that is feasible for me. I’ve noticed I eat less now simply because I have a smaller time frame to stuff my face and have more energy to work out since my body is not breaking down the 10 tacos I ate along with saving money on food.

    My reason for saying this of course it would probably be ideal to eat smaller amounts in the time frame but for a lot of people that try to get healthy they probably hit the strategy hard right off the bat, thereby going into something that is completely different from what they did before thos rushing too fast trying to get fit instead of a slow lifestyle change which is what is needed in order for your body to change. A lifestyle; not just simple meal adjustments or taking the stairs, which while those are nice you wouldn’t get the results you are looking for which will result in you getting discouraged when you completely change you’re lifestyle but don’t see results.

    The key is making small adjustments that work for you and will stay around day to day as you change both mentally, physically and willingly.

    • Hey Blake, thanks for sharing! I’m glad that incorporating fasting and eating windows has worked well for you 🙂

  • AaronRussellCox

    I’ve been 16/8 IFing for awhile now and am looking into throwing in 24 hour fasts every once in awhile. When I break my 24 hour fast and thus only have one meal (dinner) that day, should I be trying to eat my entire caloric allotment at that meal? Or how much SHOULD I be eating for that?

    • Sounds like the Warrior Diet. I’m not a fan of that one, but yes, the idea is you’d eat all your calories in one meal in the evening. I’ve written about it here: https://legionathletics.com/intermittent-fasting/

      • AaronRussellCox

        Thanks Mike!

        Have you heard of the podcast called Mind Pump? They are my second favorite source of information and you guys align on a lot of things. It’d be interesting to see if you guys ever collaborated on anything.

        • Yeah! I’ll be going on their show soon actually!

          • AaronRussellCox

            Made my day!

  • Adrian Rivera

    I used to do this “intermittent fasting” by accident. I didn’t know it was a legit thing, I only did it because I only had time for one big meal a day. Yes, this can help you lose fat, but according to my professor in Sports Nutrition, it’s not ideal for your muscles because it’s best that you get a continuous amount of amino acids throughout your day. So 3-5 meals a day is ideal for protein consumption. So yeah I don’t think anything’s special with this diet cause just like any other diet, nothing will happen if you aren’t on a caloric deficit.

  • robert

    interesting article. I wil however disagree with the diabetes thoughts. I am a faster. I was 7.7 A1C and had numbers between 180-210 for daily blood suger. I am now ~100 in the morning and see a drop into the 90’s during the day. I am scheduled to test my A1C soon and suspect it will shock the doctor at how much of a drop I have had. The author needs to not put out claims he has no true knowledge of. I am not alone, as it was anothe diabetic who told me about fasting and diabetes.

    • Hey Robert, if you feel fasting has helped and your fasting blood sugar has improved, that’s great. Many people have different responses when it comes to blood sugar control and fasting, so I definitely believe you aren’t alone.

      Have you also noticed any weight loss since you’ve started fasting? That usually has far more of an impact than the fasting itself.

  • laura E

    I’ve done the eating 6 small meals a day and although I was able to reach my fitness goals…I was constantly hungry!! I am now eating the same amount of calories but in a shorter amount of time and I feel like I’m not even dieting. I feel like fasting in the morning works best for me to have energy throughout the day, and still feel satisfied.

  • Michael

    I’ve been intermittent fasting for a few week snow Using the 18/6 protocol, last meal done by 6:00 PM. I knew going in that calorie deficit is what counts and never heard you could eat what ever you wanted. This protocol allows me to consume less calories while staying satisfied. Sure, I get really hungry towards the 16 hour mark ,but knowing that I will be eating in two hours lets me deal with it. I break the fast with a well rounded meal, then two hours later a high protein snack and finally a well balanced dinner. I also have plenty of energy all day which I never had with a straight calorie reduction plan. As you say, coupled with sensible eating, its really effective for some people. I’m glad I decided to give it a try.

    • Michael

      Oh let me add I am a dancer primarily and not looking to add bulk.

    • I’m glad it’s working well for you Michael! 🙂

  • Sam

    Everyone is entitled to their opinion, your article is your opinion because there are countless studies on intermittent fasting. However, the fact you have intended to make points to argue your case, in fact you’ve been contradictory of your own research. In one section you say people intermittent fasting lost weight but it was small, however they didn’t control calories. Well that to me suggests that actually intermittent fastin does work. Anyway 6 months of lchf and intermittent fasting I’m 20kg lighter.

    • Hey Sam, you’re right that there are a lot of studies on intermittent fasting, and I link to some of that research. You’re also right that intermittent fasting does work for fat loss so long as it helps you stick to a calorie deficit. That said, there’s nothing special about it beyond being a tool that helps some people, and it isn’t particularly useful for others. Ultimately, if you enjoy it and it helps you, go for it. If not, you aren’t missing out on anything.

      You may also want to check out this, too:
      https://legionathletics.com/intermittent-fasting/

      Congrats on your weight loss. Keep it up!

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