The difference between calorie restriction and fasting – Fasting 27

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Perhaps one of the most common questions we get is what the difference is between calorie restriction and fasting. Many calorie enthusiasts say that fasting works, but only because it restricts calories. In essence, they are saying that only the average matters, not the frequency. But, of course, the truth is nothing of its kind. So, let’s deal with this thorny problem. deathvalley

The weather in Death Valley, California should be perfect with a yearly average temperature is 25 Celsius. Yet, most residents would hardly call the temperature idyllic. Summers are scorching hot, and winters are uncomfortably cold.

You can easily drown crossing a river that, on average, is only 2 feet deep. If most of the river is 1 foot deep and one section is 10 feet deep, then you will not safely cross. Jumping off a 1 foot wall 1000 times is far different than jumping off a 1000-foot wall once.

In a week’s weather, there is a huge difference between having 7 grey, drizzling days with 1 inch of rain each and having 6 sunny, gorgeous days with 1 day of heavy thundershowers.

It’s obvious in all these examples that overall averages only tell one part of the tale, and often, understanding frequency is paramount. So why would we assume that reducing 300 calories per day over 1 week is the same as reducing 2100 calories over a single day? The difference between the two is the knife-edge between success and failure.

The portion control strategy of constant caloric reduction is the most common dietary approach recommended by nutritional authorities for both weight loss and type 2 diabetes. Advocates suggest that reducing daily caloric consumption by 500 calories will trigger weight loss of approximately one pound of fat per week.

The American Diabetes Association’s main dietary recommendation suggests to “focus on diet, physical activity, and behavioral strategies to achieve a 500–750 kcal/day energy deficit.” The ‘portion control’ advice to reduce calories has been fairly standard since the 1970s. This reduction is average calories should be spread consistently throughout the day, rather than all at once. Dieticians often counsel patients to eat four, five or six times a day. There are calorie labels on restaurant meals, packaged food, and beverages. There are charts for calorie counting, calorie counting apps, and hundreds of calorie counting books. Even with all this, success is as rare as humility in a grizzly bear.

After all, who hasn’t tried to portion control strategy of weight loss. Does it work? Just about never. Data from the United Kingdom indicate that conventional advice succeeds in 1 in 210 obese men and 1 in 124 obese women (4). That is a failure rate of 99.5%, and that number is even worse for morbid obesity. So, whatever else you may believe, constant caloric reduction does NOT work. This is an empirically proven fact. Worse, it has also been proven in the bitter tears of a million believers.

But why doesn’t it work? For the same reason the contestants of The Biggest Loser could not keep their weight off – metabolic slowdown.

Starvation Mode

The Biggest Loser is a long running American TV reality show that pits obese contestants against one another in a bid to lose the most weight. The weight loss regimen is a calorie-restricted diet calculated to be approximately 70% of their energy requirements, typically 1200-1500 calories per day. This is combined with an intensive exercise regimen typically far in excess of two hours daily.

This is the classic ‘Eat Less, Move More’ approach endorsed by all the nutritional authorities, which is why The Biggest Loser diet scores third on the 2015 USA Today’s ranking of best weight loss diets. And, it does work, in the short term. The average weight loss that season was 127 pounds over 6 months. Does it work long-term? Season two’s contestant Suzanne Mendonca said it best when she stated that there is never a reunion show because “We’re all fat again”.

Their Resting Metabolic Rates (RMR), the energy needed to keep the heart pumping, the lungs breathing, your brain thinking, your kidneys detoxing etc., drops like a piano out of a 20 story building. Over six months, their basal metabolism dropped by an average of 789 calories. Simply stated, they burning 789 calories less per day every day.

As metabolism drops, weight loss plateaus. Caloric reduction has forced the body has shut down in order to match the lowered caloric intake. Once expenditure drops below intake, you start the even more familiar weight regain. Ba Bam! Weight is regained despite dietary compliance with the caloric restriction and even as your friends and family silently accuse you of cheating on your diet. Goodbye reunion show. Even after six years, the metabolic rate does not recover .

All of this is completely predictable. This metabolic slowdown has been scientifically proven for over 50 years. In the 1950s Dr. Ancel Key’s famous Minnesota Starvation Study placed volunteers on a ‘semi-starvation’ diet of 1500 calories per day. This represented a 30% caloric reduction from their previous diet. In response, their basal metabolic rate dropped about 30%. They felt cold, tired, and hungry. When they resumed their typical diet, all their weight came right back.

Caloric restriction diets only work in the short-term, before basal metabolism falls in response. This is sometimes called ‘starvation mode’. Daily calorie restriction fails because it unerringly put you into metabolic slowdown. It’s a guarantee. Reversing type 2 diabetes relies upon burning off the body’s excess glucose, so the daily calorie-restricted diet will not work.

The secret to long-term weight loss is to maintain your basal metabolism. What doesn’t put you into starvation mode? Actual starvation! Or at least the controlled version, intermittent fasting.

Fasting triggers numerous hormonal adaptations that do NOT happen with simple caloric reduction. Insulin drops precipitously, helping prevent insulin resistance. Noradrenalin rises, keeping metabolism high. Growth hormone rises, maintaining lean mass.

Over four days of continuous fasting, basal metabolism does not drop. Instead, it increased by 12%. Neither did exercise capacity, as measured by the VO2, decrease, but is instead maintained. In another study, twenty-two days of alternate daily fasting also does not result in any decrease in RMR.

Why does this happen? Imagine we are cavemen. It’s winter and food is scarce. If our bodies go into ‘starvation mode’, then we would become lethargic, with no energy to go out and find food. Each day the situation gets worse and eventually we die. Nice. The human species would have become extinct long ago if our bodies slow down each time we didn’t eat for a few hours.

No, instead, during fasting, the body opens up its ample supply of stored food – body fat! Yeah! Basal metabolism stays high, and instead we change fuel sources from food, to stored food (or body fat). Now we have enough energy to go out and hunt some woolly mammoth.

During fasting, we first burn glycogen stored in the liver. When that is finished, we use body fat. Oh, hey, good news – there’s plenty of fat stored here. Burn, baby burn. Since there is plenty of fuel, there is no reason for basal metabolism to drop. And that’s the difference between long-term weight loss, and a lifetime of despair. That’s the knife edge between success and failure.

Fasting is effective where simple caloric reduction is not. What is the difference? Obesity is a hormonal, not a caloric imbalance. Fasting provides beneficial hormonal changes that happen during fasting are entirely prevented by the constant intake of food. It is the intermittency of the fasting that makes it so much more effective.

Intermittent Fasting vs Calorie Restriction

The beneficial hormonal adaptations that occur during fasting are completely different from simple calorie restriction. The reduction of insulin and insulin resistance in intermittent fasting plays a key role.

The phenomenon of resistance depends not only upon hyperinsulinemia, but also upon the persistence of those elevated levels. The intermittent nature of fasting helps to prevent the development of insulin resistance. Keeping insulin levels low for extended periods of time prevents the resistance.

Studies have directly compared daily caloric restriction with intermittent fasting, while keeping weekly calorie intake similar. A 30% fat, Mediterranean style diet with constant daily caloric restriction was compared to the same diet with severe restriction of calories on two days of the week.

Over six months, weight and body fat loss did not differ. But there were important hormonal differences between the two strategies. Insulin levels, the key driver of insulin resistance and obesity in the longer term, was initially reduced on a calorie restriction but soon plateaued. However, during intermittent fasting, insulin levels continued to drop significantly. This leads to improved insulin sensitivity with fasting only, despite similar total caloric intake. Since type 2 diabetes is a disease of hyperinsulinemia and insulin resistance, the intermittent fasting strategy will succeed where caloric restriction will not. It is the intermittency of the diet that makes it effective.

Recently, a second trial directly compared zero-calorie alternate-day fasting and daily caloric restriction in obese adults. The Caloric Reduction as Primary (CRaP) strategy was designed to subtract 400 calories per day from the estimated energy requirements of participants. The ADF group ate normally on eating days, but ate zero calories every other day. The study lasted 24 weeks.

What were the conclusions? First, the most important conclusion was that this was a safe and effective therapy that anybody could reasonably follow. In terms of weight lost, fasting did better, but only marginally. This is consistent with most studies, where, in the short term, any decent diet produces weight loss. However, the devil is in the details. The truncal fat loss, which reflects the more dangerous visceral fat,was almost twice as good with fasting as opposed to CRaP. In fat mass %, there is almost 6 times (!) the amount of loss of fat using fasting

The other big concern is that fasting will ‘burn muscle’. Some opponents claim (without any evidence) that you lost 1/4 pound of muscle for every single day of fasting you do. Considering I fast at least 2 days a week, and have done so for years, I estimate my muscle percentage should be just about 0%, and I shouldn’t even have enough muscle to type these words. Funny how that didn’t happen. But anyway, what happened in that study? The CRaP group lost statistically significant amounts of lean mass, but not the IF group. Yes, there is LESS lean muscle loss. Maybe it has to do with all the growth hormone and nor adrenalin being pumped out.

Lean mass % increased by 2.2% with fasting and only 0.5% with CRaP. In other words, fasting is 4 times better at preserving lean mass. So much of that old ‘fasting burns the muscle’.

What happens to basal metabolism? that’s what determines long term success. If you look at the change in Resting Metabolic Rate (RMR). Using CRaP, basal metabolism dropped by 76 calories per day. Using fasting, it only dropped 29 calories per day (which is not statistically significant compared to baseline). In other words, daily caloric reduction causes almost 2 1/2 times as much metabolic slowdown as fasting! So much for that old ‘Fasting puts you into starvation mode’.

Fasting has been used throughout human history as a tremendously effective method of controlling obesity. By contrast, the portion control strategy of daily caloric restriction has only been recommended for the last 50 years with stunning failure. Yet, conventional advice to reduce a few calories every day persists and fasting is continually belittled as an outdated, dangerous practice akin to blood-letting and voodoo. The study reports that “Importantly, ADF was not associated with an increased risk for weight regain”. Holy S***. That’s the Holy Grail, Man! The whole problem is obesity and The Biggest Loser is WEIGHT REGAIN, not initial weight loss.

Weight regain differed during fasting vs CRaP. The fasting group tended to regain lean mass and continue to lose fat, while CRaP group gained both fat and lean mass. Part of the issue was that the fasting group reported that they often continued to fast even after the study was done. Of course! It is easier than they though, with better results. Only an idiot would stop. One of the very fascinating things is that ghrelin (the hunger hormone) goes up with CRaP but does NOT during fasting. We’ve known forever that dieting makes you hungrier. It’s not a matter of willpower – it’s a hormonal fact of life – the ghrelin goes up and you are hungrier. However, fasting does not increase hunger. Fascinating. No wonder it’s easier to keep the weight off! You’re less hungry.

Calorie restriction diets ignore the biological principle of homeostasis – the body’s ability to adapt to changing environments. Your eyes adjust whether you are in a dark room or bright sunlight. Your ears adjust if you are in a loud airport or a quiet house.

The same applies to weight loss. Your body adapts to a constant diet by slowing metabolism. Successful dieting requires an intermittent strategy, not a constant one. Restricting some foods all the time (portion control) differs from restricting all foods some of the time (intermittent fasting). This is the crucial difference between failure and success.

So here’s your choices:

  1. Caloric Reduction as Primary: less weight loss (bad), more lean mass loss (bad), less visceral fat loss (bad), harder to keep weight off (bad), hungrier (bad), higher insulin (bad), more insulin resistance (bad), perfect track record over 50 years unblemished by success (bad)
  2. Intermittent Fasting: More weight loss, more lean mass gain, more visceral fat loss, less hunger, been used throughout human history, lower insulin, less insulin resistance.

Almost every medical society, doctor, dietician and mainstream media will tell you to use choice #1. I prefer to tell people to take choice #2.

2017-10-13T21:38:45+00:00 108 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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108 Comments on "The difference between calorie restriction and fasting – Fasting 27"

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ANA
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I am assiduous reader of your blog, I look forward to Thursday to read your new post. I was 128 kg and I lost 25 kg in 2 years and my weight does not decrease for 1 year. I am worried if I have my metabolism broken! I used to do only one meal a day, dinner around 1500, because I work and is comfortable like that, from Monday to Friday, on Saturday and Sunday I make a normal meal. Is it fasting or calorie restriction? I am 56 years old and I am very active, I exercise regularly. I… Read more »
Lena
Guest

Hello from France.
Ana, it seems to me that you are mixing up several weight loss methods. You are fasting, doing keto, exercising and counting your calories. Why in the world would you count your calories ? My feeling is that you are STARVING. Eating one meal a day is excellent but you have to eat enough. 1500 kcal is definitely not enough and therefore your metabolism is shutting down. Stop counting calories and add many more fat to your meals !

Stephen Reed
Guest

Hey ANA

Not answering for Jason here of course. But interested to know what you typical meals look like for a day/week?

What sort of food do you eat? You say you exercise regularly, what does that look like?

Sleep and stress? Good or not so good?

S

ANA
Guest
Stephen, thank you very much for your interest. During the two years of weight loss, I removed sugar and grains, consumed almost nothing industrialized, many vegetables, fish, chicken, no fruits, only avocado and coconut, no vegetable olives, I make LOUCARB almost ketogenic. I have no problem with stress, sleep is not ideal but has improved with Melatonin. Even though I have been in a long plateau for more than a year, I am persistent, I believe that at some point my body will react. In that time I acquired a lot of health and disposition, I do not use any… Read more »
Steve Summers
Guest

I would suggest you start to eat more as 1500 cals a day with an active lifestyle is far from ideal. There’s a strong possibilty you’re suffering from a broken metabolism. I would up my cals to 2000 a day minimum and stop the excessive 48hr fasts. You should start to feel more energetic and your sleep should improve.

MFS
Guest
Steve – I read her dinner to take place at 1500 not that her calories are 1500. She’ll need to clarify that. Ana – do you track how much of which kinds of foods that you do eat? Perhaps a different balance of those foods would be beneficial? You mention you are almost ketogenic, how are you not ketogenic? If you are close to being keotgenic but your balance is off that could be the plateau. Perhaps you are eating good healthy fats but too many then your body isn’t feeding from your body fat. You will still get all… Read more »
MAC
Guest

Just found this amazing website! I’ve been on LCHF with 18 hr IF for about 4 months, significant weight loss, but not really seen a significant change in hunger level at the 18 hr IF mark. Is my RMR suppose to slowly drop, and should I be seeing (or will see) a reduction in 18 hr IF hunger level going forward?

sten bjorsell
Guest

Maybe too much carbs in your single meal stimulates your insulin to not drop. Do a fasting insulin test. Lower carbs and be careful with proteins, no more than 0.7 g protein per kg of lean weight, measure again after 3 months both weight, waist and fasting insulin. Read dietdoctor.com and look up what Ron Rosedale says about too much proteins. Best of Luck!

glib
Guest

Oi Ana, your diet looks poor in zinc at least. It is possibly not rich enough in fat and collagen, which can be remedied with bone broth, beef and butter. You may also try to see what it is like to have two meals one day, and zero meals another day. It is also possible that you are losing fat but building muscle, and that results in zero weight loss. What you need to monitor is not your weight but your waist circumference.

Ripple
Guest

You sound like you follow the Eat Stop Eat type of intermittent fasting.. Brad Pilon (http://www.thinkfn.com/forumbolsaforex/index.php?action=dlattach;topic=627.0;attach=2555)

Alex
Guest

I don’t believe in ‘broken metabolism’. You are still living your life, you consume and burn energy everyday. Just something in your diet is out of control. You may need to track your calories more accurate (so easy to go wrong here). And for breaking your plateau you may try prolonged fasting for more then 10 days. As you have experience with 48 hours fasting you will not have any problem with that. Only your fear can stop you from doing it. But please don’t worry, it’s safe. You can google it and find out for yourself.

Stephen Reed
Guest
Hey Jason Another great post, you seem to be making a habit of it 🙂 Totally agree with all your points relating to intermittent fasting vs calorie restriction. The mechanisms and hormonal effects on the body are very different, although for many people, there is a crossover. They fast AND by default reduce energy intake. but of course, they then fall into that trap of reduced metabolic rate and all the nasties that go along with that. However, and i know that this is an approach you advocate anyway, food choices are (or should be) central to this lifestyle, whether… Read more »
Francine
Guest

Hi! I am a bit perplexed. When Dr Fung talks about caloric restriction, isn’t 16/8 IF that I do everyday, 7 days a week like if I would do a calorie restricted diet ? I don’t count calories at all, I am careful with the carbs, I don’t restrict the fats but I don’t fast for 24 hours some days, I fast everyday for 16 hours and eat in an 8 hour period. Since I do that (the same thing) everyday, do you think my metabolism rate will decrease?

Thank you

Birgit
Guest

Dr Fung, thank you for all the information you provide. It has been very helpful to me. So far, IF and LCHF combined has been the only strategy that has worked for me. However, I have been doing a water fast now for 4 days and have not lost any weight. Do you have any suggestions as to what the cause of this might be.
I usually lose about 6 lbs on a 5 day water fast. Thanks.
Birgit

Martin
Guest

Just to reassure you Birgit, it is impossible to not eat for four days and not lose weight because whilst you are not consuming calories but must burn calories to live you will be losing those calories and so losing weight. It may be that you are retaining more water and so the gain in body fluid is disguising the fat loss.

Birgit
Guest

Thank you, Martin. I am on my last (7th) day of fasting this go round. I have now eliminated all artificial sweeteners and reduced my salt intake. As a result, I have lost 2 lbs.

Since starting IF with LCHF, I have lost 50 lbs, but have plateaued for the last 3 months. I plan to continue IF by rotating 7 days of water fasting with 2 weeks of alternate day fasting and LCHF.

Star
Guest

If you were having sweeteners during your fast, then it was not a water fast. Even that small addition can halt weight loss on the scale. Next time, try just water or coffee, tea, and a little broth. The difference is monumental.

Rajesh Pankaj
Guest
Hi Dr. Fung, This is Rajesh from India, a big fan of your work. I have T2D since 2013, getting treated with Metformin 500 mg XR twice after each meal. I also tried SU-JOK therapy for almost a year with no significant improvement. But with all the restrictions, this September I became depressed thinking that I never getting out, I never be the same as earlier. Then I came across Prof Roy Taylor diabetes research online which opens my eyes. I immediately started my dies limiting it to more or less 800 Cal, mostly comprises of green vegetables(boiled n raw).… Read more »
Henry
Guest

I’ve met a number of vegetarians [including Indian vegetarians] who practice low carb and/or intermittent fasting. I would stick to as much avocados, coconut, nuts, vegetables, and legumes that you can and avoid rice and wheat. Also, the higher the carb content in the diet then the more there needs to be more emphasis on fasting, exercise, and proper sleep. good luck

Rajesh Pankaj
Guest

Thanks a lot Henry. That’s what I am following except No Fruits and No Legumes. I am missing Bread and Rice. Thanks Henry I will experiment if adding legumes would be beneficial for me. God Bless!!!

Birgit
Guest
Namaskar, Rajesh. May I suggest that you try to eliminate or at least reduce the wheat and rice. Eat channa and beans as well as nuts such as almonds, (not cashews and peanuts), and drink full fat milk and plain lassi for protein. Tofu is a good vegetarian food with high quality protein and very few carbs, I don’t know if it is available in India. Also, increase your fat intake with ghee and coconut oil. I have had to experiment for several months to discover what works for me. Everyone’s situation is different. I wish you good luck. May… Read more »
Rajesh Pankaj
Guest

Thanks Birgit. Those are exactly same except Tofu, milk and Lassi. Instead I have boiled and roasted Soya Chunks once in 2-3 days. If anyone could advice that can bread (Flatbread/Chapati of any flour)be added to food or should I forget it forever?

Birgit
Guest

Rajesh,

For now, avoid all grains. When your health has recovered, you might try to experiment with incorporating limited amounts. The Diet Doctor has a number of recipes for low carb Bread. I have not tried any, but the pictures look good.

Rajesh Pankaj
Guest

Thanks for helping me Birgit,

When one can say his health is recovered? My RBS dangle around 150 mg/dl(without any diabetic medicine). No visual FAT on body anymore. Any suggestion?

Babu
Guest

I am DT2 for past 15 years. Started the 24 hrs fasting with only non-caloric stuff, water, diet ice tea, tea etc. I am on Metformin 1000 twice a day and Junevia once a day. Both of them are extended release. My concern is that If I an not eating anything for 24 hours, taking medicine may cause my blood sugar to go very down.

Can anybody please please answer one simple question? Should I take my daily medicine while fasting?

Danielle
Guest
I am not a doctor and this is not medical advice, but you need to talk with your GP about lowering your Junevia. It is not a good idea to fast on it in general terms but depends on your dose and your blood sugar readings so you need to review it with your doctor who prescribed the medication. Metformin is usually the last drug to be eliminated once your hbA1c is <6.8 but again you need to discuss specifics with your doctor. You need to fast so you need to find a doctor who is supportive of that. If… Read more »
KibbyRose
Guest

So are the results as good if you do a daily 16-hour fast, instead of a 24-hour fast 2 days a week?

Alicia
Guest

I would also like to know this. Or an 18/6, which is what I do every day. FWIW, I am a 32 year old female, 5’6″ tall, 135 lbs.

David
Guest

The precise details of the benefits of relative fasting schedules don’t seem well-documented at all. Right now scientists are just measuring fasting versus continuous eating, not type I fasting versus type II fasting.

IMO, just do whatever fits your schedule. I do personally assume that longer fasts yield additional benefits, but they’re heard to schedule.

glib
Guest

I agree. we are all different, and summer me is different from winter me. In summer I can go 36, do not even notice it. In winter I get cranky at around 20 or even 16 hours, and sometimes I just do a fat fast, where I eat a couple tbsp of ghee or coconut oil at 10am and 2pm (going dinner to dinner).

RP
Guest

I have been doing 16-18 hours daily fasting for almost 2 years now with GREAT results. I eat 2 times a day: i break my fast (after a fasted workout) around 2 PM and i eat dinner at 7-8 PM (and some fruit snacking in between) and then i fast again from 8 PM to 2 PM. I feel great, i have low bodyfat percentage and i am pretty athletic (due to strength training), no muscle loss, no hunger etc… so from my own experience i can surely tell that 16-18 hours daily fasting works great.

sten bjorsell
Guest
It will take at least 12 hours “run in time” before insulin falls enough to get the liver to empty glucose constantly. Once it starts emptying it can go on for 2 days and more for those with an enlarged liver, which keeps insulin from dropping further and reduces or prevents fat burning. Hence longer periods are more effective. Blood sugar can even go up during 2-3 days fasting for those with high insulin resistance/enlarged liver, until the stored glycogen eventually runs out. Note, as pointed out before, diabetics-2 normalizes blood sugar through a GBP operation! But not through the… Read more »
seebrina
Guest
You have to try a fast and see how it effects you and gives you the results you want or not . If not Do a different length fast. What works for one doesnt work for another. I just did back to back 48 hour fasts, eating one day in between. Iam now doing 24 hour fasts everyday until I do another 48 hour fast next week. My fasting BS finally came down to 92/ I really want it to stay there or a bit below. This am after 1 LCHF meal yesterday it was 102. Its progress. Shorter fasts… Read more »
Marguerite
Guest

Is there a practical way yet to measure insulin instead of blood glucose as was done in the two studies you mention? I’d love to be able to see what was happening on the insulin front in my body .

Leah
Guest

Thank you Dr Fung! You are my health hero! I am so thankful for your work! I need to remember that with fasting, even when I am not loosing weight I am still healing my body. I have lost 30lbs this year thanks to you. Its very slow going but its going and not coming back.

Eli
Guest
Dear Dr. Fung Is body temperature a good measure of “starvation mode”? I have been doing very well on an LCHF diet for 9 months, the last 4 also with added intermittent fasting. I lost 15KG and lowered my HbA1c from 7 to 5.7. However, the last month or so the weightloss stopped and I even started gaining a wee bit. Reading through your blog and book about Compensation, I thought perhaps my metabolism was slowing down – so I measured my temperature. I was very surprised. it was 95.5F (35.3C). So I started measuring constantly and noticed that I… Read more »
sten bjorsell
Guest

One simple check is fasting blood sugar morning after eating days. If over 100 you are probably eating too much protein, that converts to blood sugar. Longer fasting times will also help.

Phillip Actor
Guest

GNG is NOT at all a reason as has been amply proven in recent science. It is a demand driven feature. The only real reason to not outdo protein versus fat in LCHF is because protein tastes much better, but only brings half as many calories per gram. Zero carbers do excellent on 2 kg of meat per day for a reason and they tend to be in ketosis permanently. Not possible is protein converted to blood sugar by magic instead of GNG 🙂

Roger Bird
Guest

OMG: “success is as rare as humility in a grizzly bear.” You are one funny and creative dude, Jason.

Lynn W.
Guest

Thanks Dr Fung for your wonderful posts. Not only do I learn, I laugh out loud!

Chris S
Guest
I just returned home from surgery for a complete hysterectomy. I have been morbidly obese for about 25 years or so, early signs of diabetes, creeping A1c, thyroid meds, blood pressure. I realize that I have been insulin resistant for much longer than that. I am 64 and have been given all manner of advice on taking the weight off since I was 10. In May I stumbled upon this wonderful community of people who are passionate about health first – i.e. the patient, and then statistics and other factors later. I began to fast for 24 hours three days… Read more »
Pete
Guest

Fantastic! Check out the Fung Shweigh group on Facebook as a support tool.

Stephen T
Guest

Chris, the food given to diabetic patients must constitute cruel and unusual punishment. Complete madness.

Well done on your choices and progress.

Maria J
Guest

Excellent read. Favorite laugh, “Goodbye reunion show.” Thanks for all you do.

Roger Bird
Guest

What is IER and CER? I spent 10 minutes looking for an explanation and ended up having to trust the implication of the text compared with the graph.

PhilT
Guest

Intermittent and Continuous Energy Restriction – IER and CER

Roger Bird
Guest
I have been intermittent fasting (and a few extended fasts) for 6 months and 3 days. Since I am human, I have also fallen off the wagon now and then. This falling off the wagon now and then has actually been a good thing. It has taught me a lot. One thing that I have learned is that sugar, especially fructose, makes me hungrier and destroys my will power, both. First, fructose, even in the form of fruits like grapes, destroys my willpower, and I do not mean just about eating. I struggle and usually win with getting to bed… Read more »
Michelle
Guest

I am not sure I fully understand. Let’s say I follow a 23/1 fasting protocol everyday, but also restrict my calories to a 40%-50% deficit everyday. Also, my only meal of the day is very low carb, high fat (keto). Will I slow my metabolism down over time?

JohnM
Guest

Your metabolism will NOT slow down after a substantial calorie reduction unless your insulin level is also high. Insulin controls the release of fat. Fasting with HFLC combined with a narrow eating window ensures that insulin stays low so your body can use fat as it fallback energy source. When fat can’t be used, the body’s only other choice is to reduce your energy output by putting the brakes on your metabolism.

Pete
Guest

No, because any energy you need can come from stored body fats once you deplete your glucose as fuel, metabolism has no reason to slow down.

Michelle
Guest

Thank you, that’s what I thought I had understood. I feel great and my energy level is very high!

ANA
Guest

Pete and Michele, it’s exactly my case I put my doubt in the first post. Thank you!

sten bjorsell
Guest

Agree, it is perfect at least to start. If weight loss stalls after a while reduce proteins. Check out Jimmy Moore and Ron Rosedale for more about it.

kent
Guest

I echo this question. Having read every word that Dr. Fung has written, I still don’t know the answer. I suspect that total calorie intake doesn’t matter, but I would still like a definitive answer from Dr. Fung on this topic.

Abi
Guest

So what I get out of this is that daily caloric restriction is CRAP. Is Caloric Restriction as Primary really the official term? Did the geniuses who came up with this bother to read their oh so clever acronym?

Thanks Dr Fung, I learn a lot from you and the humour makes the points stick.

Carlos
Guest

Part of Dr. Fung’s witty style.

He (as far as I know) chose the acronym deliberately for comic relief reasons.

And the alternative theory he proposed, Hormonal Obesity Theory is…yes, it’s HOT.

Anistemi
Guest
As has been referred to by a handful of people who have responded to this post – there is a third choice one can consider, apart from CRaP and Fasting (intermittent or otherwise), and this is the Low Carb, High Fat (LCHF) diet a.k.a. the Ketogenic diet. I began with fasting myself, and found this to be very challenging. But then I was introduced to the LCHF by other Fasters in a chat room I joined, and I found that I could achieve the same results by pursuing a Ketogenic or LCHF diet than I could with fasting. I have… Read more »
Deepak
Guest
Dear Dr. Fung, firstly.. THANK YOU! I think I have managed to read most of your blogs, watched your various videos on you tube and your books on Obesity and fasting and I had a question. background: I have been T2D since 2003 on standard medications and injection till 2008 with by weight going up to 98 kg. With some half-assed reading, primarily CraP, my weight came down to 82 kg and only on metformin until Dec 2015. From Jan, I began reading again with renewed vigor on how to get my weight (fat%) further down. But still on CRaP,… Read more »
Bre
Guest

Hi,
My question about all this intermittent fasting is: Is IF beneficial if you are not doing the low carb diet as well? I eat gluten free, but I do eat fruit and sometimes small amounts of grains. About 100 grams of carbs a day. Would intermittent fasting benefit me, or would it just stress out my body since I am not keto adapted? Thanks for any insights!

Stephen T
Guest

Bre, I started by changing to a low carb, high fat diet and found that I was easily and naturally going 12 – 14 hours without eating because eating a higher fat diet satisfied my appetite. I later moved easily into fasting because it was easy to add another 2 – 5 hours on top. So, fasting benefits anyone, but a diet that doesn’t make you feel hungry obviously makes fasting a lot easier.

Wenchypoo
Guest

Fasting seems to work no matter WHAT your starting point–I have a girlfriend who is hopelessly wed to the SAD diet, so I turned her onto intermittent fasting instead of the continued uphill battle to try to clean up her diet. In spite of eating SADly, she has lost weight, and her blood sugars have improved. I imagine the lack of stress from me trying to correct her diet also played a role.

She’s continuing to lose weight and improve as we speak, despite all the junk foods she eats. GO FASTING!!!

Sonya
Guest
Dear Dr Jason Fung, I have tried fasting for 24 and 48 hours, both felt good and increased my energi levels. However, during periods when I practiced intermittance fasting, I felt changes in my bowel flora, and I developed both vaginosis and yeast infection. Now I am a bit hesitant of returning to my fasting regimen. I wonder: could my problems be due to too much coffee on an empty stomach while fasting? Have you experienced these sort of problems among your clients? I have eaten a low carb high fat diet for almost five years. Thank you for your… Read more »
thebigpicture
Guest
I do in general agree with fasting and a ketogenic diet, but it’s not as easy as it might seem. I’m overweight but not obese, have twice tried fasting beyond 24 hours and failed. I made it to about 36 hours each time before giving in. It’s a combination of hunger, emptiness, and a strange feeling of being tired and alert at the same time. You literally can’t sleep, nor can you do anything else. Eat a meal, and I instantly feel full, satisfied, and ready to either work or sleep. As far as ketogenic diet, again, not so easy.… Read more »
Stephen T
Guest
I think a 36-hour fast is success. I don’t even try to get past 16 – 20 hours. You’re right that refined carbohydrates are everywhere, but I now find it easy to ignore them. It is shocking when you realise how much of what we eat is sugar-laden junk and it explains the obesity rate. Slipping up at Christmas might set you back a couple of days, but I can’t understand why you say a year? Some people can get away with eating badly for a while, but it’s probably not doing them any good in terms of visceral fat… Read more »
George Thomas
Guest

It’s not that hard to dodge refine carbs. Sounds like you’re just making excuses.

Raj
Guest
Hi Dr. Ginger I have been motivated by your articles to do fasting! But in my first attempt I fast with only water for 40-42hrs. I wasn’t feeling too weak but may be tired walking around. However (no) thanks to a diabetes exhibition in the mall I ended up checking my glucose level out of curiosity and it was 3.9. The sales lady who was selling the kits was somewhat surprised and asked me go eat something! With that remark it suddenly seemed I was too tired, weak and I broke the fast right away with bread. Then I felt… Read more »
sten bjorsell
Guest
Raj, Next time drink more water, it helps. If you eat less carbs and more fat for a few days before you start next fast you may not feel weak after 40 hours time as you have already adapted the body to burn more fat than usual. Fasting gradually becomes “pure” fat burning, once (diabetic) stores of glycogen and liver fats and ARE GONE AND proteins scavenged by autophagy has been used up. With LCHF as starting point you really get a flying fast start! Same fuel (fats) but from different sources. Wish you the best of Luck!
Christine S.
Guest
Raj, normal fasting glucose levels are between 4.0 and 6.0. And glucose meters may not be that accurate – Canada follows the ISO 15197:2013 standard, which says that meter readings need to be within plus or minus 15% of actual! Other countries may follow different standards. I would say your blood glucose reading was just fine in that situation. A blood test in the lab is the only accurate measurement. I have Type 2 diabetes, diagnosed 12 years ago, and test multiple times a day, but I tend to go with how I feel more than what the meter says.… Read more »
Raj
Guest

Just discovered there is a study result posted as table 3 in Dr. Jason article of 1 May 2015 (Fasting 4). The subjects’ average glucose on day 2 exactly same as what I observed in my case!

That’s reassuring.

Raj
Guest

Sorry the name got auto corrected, I didn’t notice!

Raj
Guest

Thanks Sten, Christine!
Yes my main concern was if I had not eaten the sugar level was low enough to cause some serious trouble such as fainting. I think I can stretch myself bit more next time. I am not vegetarian but not much of fats in my diet right now. I’ll keep your comments in mind. 84 hours seems like long long time impressed you pulled it off!

Good luck with your efforts

Buttercup
Guest
Thank you very much for this article, it was a very interesting read. I visit this website on a regular basis to learn more about fasting and other topics concerning metabolism. I’m an intermittent faster (/low carb) from Germany and I’ve got a question. When people fast for 3 or 4 days a week, usually the weekly average intake of calories will be decreased automatically. Would it be better if one tried to avoid this to happen and increase the daily calorie intake to even out the zero-calorie days? Or is there any calorie deficit one shouldn’t surpass? Right now… Read more »
JohnM
Guest
Weight loss will occur when the body is faced with a calorie deficit AND low insulin level. Low insulin level allows your body to use stored fat to supply the energy difference. If you body requires 2,000 calories each day, and you reduced consumption to 1,500, the remaining 500 calories would be supplied from fat. As far as exercise is concerned, I would suggest that you consider the resulting calorie burn as a weight loss bonus. By not eating replacement calories you also reduce muscle glycogen levels sooner and get into fat burning sooner. Exercise is best used to retain… Read more »
Buttercup
Guest

Thank you very much for the reply. Then I will continue with my fasting schedule. I just wondered whether my deficit was too large. I feel good and I love to fast on consecutive days. I’ve been doing this for some months now (more for health reasons than weight loss) and I didn’t want to change to some other schedule.
Cheers!

Buttercup
Guest

I need to correct something there: of course I want to lower my body fat percentage… Sorry about that.

Elizabeth Fen
Guest
I am T2D for the past 7 years. As Dr Fung had mentioned my medication had only gone up.I started with metformin500and750 ,now it’s 850 twice a day.i have not been regular about exercise or dieting. My weight 70kg went down to 62 kg and remains 65 kg ever since I becameT2D. I am 5’6 and doctors say my weight is o.k. I have started the intermittent fasting with 14 hours just to get my body used to the idea. Is it necessary to go off carbs totally. During my meals I consume some carb.what could be the best fast… Read more »
Tamara
Guest

Hi dr Fung!
I am on my third week of eat-stop-eat protocol (dinner-dinner ), and I feel increased hunger and fatique the day after fasting. I even experience some carb cravings ( LCHF for 8 months, without cravings) Funny thing that during fasts everything is just fine. But the next day I have zero energy…
Can it be caused by depleted liver glycogen? I rarely eat more than 80gr total carbs per day, usually even less. At the moment this is my only theory…

Walt
Guest
@Tamara, I have exactly the same results you describe, and this after multiple extended fasts, my feet (especially) and hands are constantly cold. I find I have to wear wool socks at night. For instance today is my third straight day of not eating…at all. Distilling, from all of Dr Fung’s blogs / Youtube vids and his two book, there are carbs and then there are refined carbs. While 80g of carbs/day is nowhere near ketogenic if it is comprised of salads and not potato chips that should suffice. There are those on here that believe the ‘true way’ is,… Read more »
Tamara
Guest

I no longer aim for ketosis, I stick to LCHF because it is so great not to be tempted by sweets and junk food. Its like my body works the way its supposed to.
But the after-fast fatigue is bad. Another week past by, and its still bad….

Etienne Juneau, PhD
Guest

Absolutely epic post Jason! My clients ask me all the time about “stavation mode”. I’ll point them here.

Btw, the “Zauder” 2000 study on your “Metabolic changes over 4 days of fasting” image should read “Zauner” (with an N) unless I’m mistaken.

Cheers and keep up the good work!

Etienne

Kok-Hong Wong
Guest

Even more interesting is the effect of prolong fasting with correct refeeding.

In this interview Dr Valter Longo compares the difference between chronic calorie retriction vs short term fasting/refeeding…see 1:10:00

https://www.youtube.com/watch?v=d6PyyatqJSE&t=1406s

DIANA BRAVO
Guest

Dr Fung, you should contact the biggest looser and put your plan against there’s. So that America can see which is the better way. Of course it would probably ruin their show…

lynn
Guest

I really missed this week’s blog . I also miss his comments.

Ketogenic diet
Guest

Really good article. Thx for the same. My Qs is, during fasting, the uric acid level is increased and body will be getting into ketosis mode. Can the person who is having high uric acid level, follow the intermittent fasting?

In intermittent fasting, which window will give best result like 16:8, 20:4 or 23:1…

Please advise and thanks in advance

Walt
Guest
First, lest I forget, you probably need a copy editor. Few, if any, word processors or text editors can deduce language structure (verse correct spelling) I have two questions. Dr Joseph Kraft showed that type 2 diabetes could actually be determined upwards of a decade before any indication showed up in a routine fbg test by using a glucose tolerance test instead. This effect was even put to graph in earlier blog posts where fasting blood glucose is relatively flat until BAM, it goes vertical years into the chart. This is precisely what Dr Kraft discusses. If people took action… Read more »
Guest
Guest
I can’t answer for fung, but I was diagnosed with T2D two years ago. The day it happened I was admitted to an emergency room with a fasting glucose of 200+ the morning of my admission. Sadly, I can’t remember my a1c at admission, but it can’t possibly have been good. I’ll spare you the long version of what I’ve been up to over the past two years, but suffice to say, my last a1c test was 5.1. Over the past two months I have never measured a fasting glucose above 94 and the single highest blood glucose I’ve managed… Read more »
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Maureen
Guest

Thanks for the great post Dr Fung. One question I have is in regard to the increased metabolic rate that fasting produces. Have any studies been done to see how long the body maintains this increase? Reduced calorie diets decrease metabolic rate even up to six years. But I have seen nothing about how long the increased metabolic rate continues. Thanks!

Jordan
Guest
Hello Dr Fung, I have a question about caloric intake on Intermittent fasting vs fasting. Here is my understanding so far: When fasting for 36, 48 hours, or however long, one would abstain from all caloric intake during that period. The body does much to maintain itself by burning fat for energy, producing growth hormone, etc. When breaking the fast, one would resume regular caloric intake enough to satisfy for one’s daily macros, rather than enough to compensate for the lack of caloric intake during the fast. So over a week during which one would fast, one’s weekly caloric intake… Read more »
MachineGhost
Guest

The trick is to incur negative energy expenditure without decreasing TEE that would negate it. So if your goal is to lose body fat and not maintain or gain, you could still use a calorie deficit when refeeding. Since the body cannot access more than around 31.4 +- 3 calories per pound of fat per day under non-fasting SAD conditions, I would target a deficit no larger so TEE won’t be decreased.

Jan Hansen
Guest

Hi,

I’ve followed your advice, and my bloodsucker has improved, but ! I’ve been intermittent fasting i 4 weeks, and I’ve cut out all carbs and sugar, but it seems like my sugar storage is unlimited? How long does it take to get rid of it? I’m not taking medication, but I do take Gymnema, Chromium and Cinnamon that is working to a certain extend.

Thank you for all your information/education, is it desperately needed !
I’m Danish, and you won’t believe what the Danish diabetes association is recommending to eat, it’s sick ..

Vadym Graifer
Guest
Intermittent fasting was exactly what made a world of difference for me and my health quest. Short story: – Diagnosed with diabetes in 2013, weighing 240 pounds, A1C at 9%. – By adjusting a diet, replacing sugary and starchy food lost about 24-25 pounds over the course of 2 years. – Discovered Intermittent Fasting in the spring of 2016; lost 50 pounds over the next 7 months. Sitting at 165 pounds now, A1C dropping steadily and is under 6 now. Off hypertension medication as it’s not needed anymore; Metformin went down from max dose to a min (500mg a day),… Read more »
Mike G.
Guest
Dr. Fung, I can’t thank you enough for the wealth of information on your website. It has been lifesaving! I am a kidney transplant patient (9 years now!) who has been struggling with NODAT T2D. Prednisine really kicks my ass and over the years my total daily insulin dose (basal + rapid) has increased to 108 units. I have been on LCHF + IF for 3 months (23 hrs fasting with a 1-hr feeding window). Lost a lot of weight and waist girth and got my insulin down to 40 IU. Then I went on my first 5-day fast. Totally… Read more »
Wangiko
Guest
Dr. Fung, I have been on the LCHC Diet with the intermittent fasting for 15 days. I lost 5 pounds so far but am having problems with my bowel movements. I have relaxall every day morning and evening to regulate me. I fast 16 hour fasts and 24 hour fasts. Not sure if I am doing them correctly. I have the bullet coffee in the morning with cream, butter and coconut oil. Then drink green tea in the morning until about lunch time. I have broth after that two or three times until the evening. I have a low carb… Read more »
Hari Ganesan
Guest
Hi doc , Have been seeing all your videos through facebook and whatever resource i have. I believe whatever you had said made a lot of sense to me . But i have one big question . i could not get your email id to ask this question . So kindly take time to answer this, i would be very happy to see a reply from you even though i understand your have a very tight schedule. If We Fast for longer periods one of my doctors here who is an gastroentrologist suggests that i would develop gastricitis and duodenogastric… Read more »
Dan
Guest
I hope someone can help me/ clear something up. Apologies if it has already been answered and would appreciate a point in the right direction. I am a 34 Y/O male, 6 ft and weigh about 189lbs with roughly 18% body fat. Im trying to loose BF and eating a LCHF/Keto diet, Intermittent fast Every Day, weight train in gym in the morning 3 times p/w, but am struggling to lose any weight. In fact i have noticed a slight increase in weight over the past month 🙁 I am not sure what is happening!? I was a victim of… Read more »
EC
Guest

Hi!

I’ve been following this blog and the YouTube videos. I started with fasting blood sugars of 225 and am now regularly around 85 mg/dL.

Last week I tried going from alternate day fasting to a 3 day fast. My blood pressure went up and my sugar on day two was 63. Is this common? What could be causing that? I meet with my doctor to get my A1C re-checked this week. It would be great to have any insight on this issue.

Thank you!

David Nyman
Guest
OK, I promise you I’m not trolling just confused. I’m a successful IF-er myself, so I’m a supporter not an opponent. But I don’t understand the point about BMR. Of course, if body mass falls, so does the requirement for energy input to maintain body mass, other things being equal. And I fully accept that eating frequently as opposed to IF produces very different hormonal outcomes (and beneficial in the case of IF, else I wouldn’t be doing it). But IF increases BMR? What are the measures? In my case, a lifetime’s exercise habit has left me with a resting… Read more »
Rustybeth
Guest
David Nyman: BMR is affected by your body composition, and it takes more energy to maintain muscle than it does to maintain fat. Your BMR is made up of many factors, the biggest of which is your brain’s operation, then you have body functions, and then you have cell maintenance. So the loss of fat as body mass falls is not going to significantly impact your BMR to the detriment of your metabolic rate. The expression of growth hormone during the fasting state will stimulate muscle activity and even growth (by harvesting amino acids from the metabolized fat stores), and… Read more »
Mike
Guest

Hey!

First off, I love your material! I have read the latest book, and am catching up on your blog posts now.

I have a question for you, what do you think of the latest news that compares IF to restriction and has data that contradicts itself, and this post:
http://www.consumerreports.org/dieting-weight-loss/intermittent-fasting-no-miracle-path-to-weight-loss/

Your data makes more sense, but wanted to see what you think.

Britt
Guest

Yeah, calorie restriction is bogus. It’s failure rate is nearly 100%! And we’re to believe it’s only because “fat people aren’t trying”. I totally relate to always being hungry on a calorie-restriction diet. I fasted for a few days and since then, I almost never have hunger pangs no matter how little I eat. I’m excited to fast again and set up a regular routine of a couple days of fasting per week. Most importantly, hoping to see plenty of weight loss!

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