Fasting Notes

by Jimmy Akin

in +Religion, Diet, Food and Drink, Science

IMG_1953If you follow me on Facebook, you may have seen that I’ve recently been chronicling my weight loss journey there, and there’s been a lot of news to report! (The picture is one of me now that I can fit into a shirt that just has an L on the label–no X or XX.) Update: I’m now wearing medium shirts, so I’ve changed the picture.

A few months ago, at the suggestion of my physician, I began to practice intermittent fasting, and it’s really accelerated my weight loss. At the time of writing, I’ve lost 29 lbs 38 lbs 47 lbs 58 lbs 69 74 lbs (it may be more by the time you read this), it’s produced other health benefits (including improved sleep and energy), and it’s been surprisingly easy (very little hunger at all).

I plan to do a blog series about my experience in the new year, but folks on Facebook have been asking a lot of questions, so I thought I’d jot down a few notes here until I can launch the series.


You’re really fasting?






Are you hungry all the time?

Not at all. I was surprised at how little hunger I’ve had. I had some for the first few days after I altered my eating pattern, but they went away quickly.

I called a friend who does a lot of fasting, and he said his experience is that hunger is largely a matter of habit. When your body is used to getting a new influx of calories, that’s when it sends the “It’s time to eat now” hunger signal. If you ignore that signal when it comes, it will re-set to the new normal and stop sending you the hunger signal at the old times.

I later asked my doctor about this, and she said it has also been the experience of her patients who have tried intermittent fasting.


What do you do when hunger does come?

I may drink non-caloric beverages to fill up my stomach (water, tea, coffee, no-calorie sodas with stevia [a natural, non-caloric sweetener]).

I also just ignore it, because hunger isn’t a constant. It comes in waves, and my experience has been that if I ignore it for 20 minutes, it will go away on its own.

Really, though, I’ve been amazed at how little hunger there has been.


Jimmy, I’m concerned for you. This sounds unsafe.

Thank you for your concern, but please don’t worry.

First, my doctor was the one who recommended it.

Second, I’m doing it under a doctor’s care, so all the right things are being monitored.

Third, it’s actually very safe (see below.) Fasting is actually a normal part of human experience. We’re designed for it. It’s just not part of our culture (which is a big part of our culture’s problem with weight management and various health issues).

Fourth, in case of problems, fasting is the easiest thing in the world to stop (also see below).


Won’t fasting slow down your metabolism?

Not if you’re doing it right. Calorie restriction will slow down your metabolism, but calorie restriction and fasting are two different things, and the body responds to them differently.

If you reduce the number of calories you eat at each meal but you continue to eat 3-7 times a day then your body will think food is in short supply, but that you do have a supply of it. In that case, your body will adjust your metabolism to the supply it thinks you have. You will get sluggish, irritable, and may feel colder than you otherwise would.

But if you stop the calories, your body will think you don’t have a food supply and that it needs to start burning fat, which is what the fat is there for.

Your body doesn’t know that we aren’t still living in caveman days, so if you aren’t putting new calories in, it think that your food supply has run out and that you need to go kill a bison or something.

It therefore does things to help you be a better bison hunter, like keeping your metabolism revved up.


Won’t fasting cause you to burn muscle instead of fat?

No. We can show that people who are fasting aren’t burning muscle because when the body burns protein (the stuff muscle is made of), there is a byproduct known as urea. When people are eating normally, they have substantial levels of urea in their blood from the protein they eat. But when they start fasting, the levels of urea in their blood plummet, showing that they are not burning protein–either from food (which they aren’t consuming) or from muscle.

See this video for more info on that.

Bottom line: You need muscle to go hunt bison, so your body burns the fat and preserves the muscle. The purpose of the fat is to be burned as fuel, so that’s why the body burns it. The purpose of muscle is to help you catch bison, so the body leaves it alone. It will only turn to burning muscle if you’ve used up all your fat and it has no other choice.


Won’t fasting make you mentally fuzzy or give you headaches?

No. You need mental clarity to hunt bison, so your body has an incentive to keep you clear headed. Giving you less clarity or headaches would interfere with a successful bison kill, so your body won’t do that to you.

Or that’s been my experience. If you are used to consuming something (e.g., coffee) that will cause headaches if you stop, and if you then suddenly stop, then you may get headaches. However, it’s not the lack of calories that’s causing the headache. It’s the lack of the specific thing that’s causing the headache.

Also, since coffee is a no-calorie beverage, you can have it when you fast! (Just don’t add cream or sugar.) So you can avoid the problem.

People generally report more mental clarity when fasting, not less, which makes sense if your body is preparing you to go kill bison.


Isn’t fasting unsafe?

For the vast majority of people, no. See previous answers.

Also, billions of people fast, at least occasionally. Catholics, Jews, and Muslims all practice intermittent fasting.

And we’re built for fasting. Our bodies are made to put on fat in times of plenty so they can use it for fuel when the food runs out. That’s why it’s there in the first place. Feasts and fasts are normal parts of human experience, historically speaking, and our bodies are built to handle them.

However, there are some medical conditions in which people either should not fast or should do so under a doctor’s care. This is particularly the case when you are on medications that you may need less of when you fast. For example, diabetics are likely to need less insulin, people who take blood pressure meds are likely to need smaller doses. If you don’t adjust your dosages, your blood sugar or blood pressure might go too low. Therefore, consult your doctor.

However, needing less of these medications is actually a good thing. It means your health is improving! Yay!

More info on these conditions in the resources recommended below.


So what kind of fasting are you doing?

Currently I am eating one meal a day with no snacks. (BUT SEE HERE ON SNACKING.)

The one meal I eat is not calorie-counted, but it’s obviously way less than what I would eat during the course of an ordinary day of eating.

It’s also usually low carb/high fat, though I don’t have to be as strict about that as normal.

I eat it in the evening, but you can do it whenever in the day would suit you.

I also stay hydrated and take my normal vitamins/nutritional supplements.


How is eating a meal a day fasting?

It’s an intermittent fast–meaning that I do take some food on a regular basis (in my case, currently once per day).

It’s not a long-term, unbroken fast.


Are long-term, unbroken fasts dangerous?

Well, you will eventually need new calories, but people can go for much longer than they suppose and be perfectly healthy on a fast.

Some individuals literally fast for weeks or months.

The longest fast on record was a Scottish gentleman who–under his doctor’s care–only took water and vitamins for 382 days (no food for more than a year!) and was fine. He also went from over 400 lbs to under 200 lbs, which was the point.


I’m interested in fasting, but I’m afraid to start all at once. Is there a way to work into this easily and gradually?

You bet! That’s what I did. I took it in stages:

  • I started with a low carb/high fat diet so that, without the carbs, I wouldn’t have the insulin spikes and the resulting hunger they cause (this is why people are famously hungry an hour after eating Chinese food: the high carbs lead to high blood sugar, that leads to insulin release, that leads to a blood sugar crash, and that leads to hunger to get the blood sugar back up)
  • Then I cut out all snacks, so I was eating only three meals a day.
  • When hunger did come, I would drink non-caloric beverages or just ignore it since I knew it would shortly go away on its own (see above).
  • Then I dropped breakfast (the idea it’s the most important meal of the day is not true, which is why so many people find it easy to skip).
  • Once I was used to eating two meals a day (lunch and a late dinner), I started moving lunch later and later in the afternoon, to narrow the window in which I was eating and extend the period each day in which I was fasting.
  • Once “lunch” was within a few hours of dinner, I dropped “lunch.”

This stepwise approach was so successful for me that, the day I first went to one meal, I wasn’t even hungry at dinner time. But it was when I had determined to eat, so I did.


I don’t think I could do low carb. Would that stop me from fasting?

No. Fasting is just not eating, so you can do fasting no matter what diet you normally prefer.


What if I encounter problems fasting?

I love the way the book I recommend below puts it:

What happens if you do get hungry or don’t feel good while intermittent fasting? Ummmm, hello, McFly? You eat something! This isn’t rocket science, people (The Complete Guide to Fasting, p. 21).


What are some of the benefits of fasting?

They include:

  • Weight loss
  • Lower blood sugar
  • Lower insulin resistance
  • Lower blood pressure
  • Lower inflammation
  • It may provide added protection against cancer
  • Greater mental acuity
  • You don’t spend as much money on food
  • You don’t spend as much time procuring, preparing, and consuming food
  • You get the chance to practice self-discipline

More info on some of these here.

In my case, I also found my sleep improved (which is noteworthy, because I’m a lifelong insomniac).


If we’re built for fasting and if it has all these benefits, why don’t we hear about it more?

Several reasons. Among them:

  • Big Food has zero interest in not selling you food. It spends enormous amounts of money in advertising trying to get you to buy stuff to eat.
  • Therefore, when its “eat all day by adopting a grazing strategy of three full meals plus three or more snacks” causes people to gain weight and have health problems, it’s solution is not going to be “don’t eat.” It’s going to be “eat something different” (e.g., expensive diet products or the latest fad’s “superfood”).
  • Big Pharma has zero interest in not selling you drugs and medical procedures. Therefore, if you’re suffering from obesity and medical problems, their solution is not going to be fasting but “what kind of drugs or medical procedures can we sell you to address or manage these?”

As the result of economic incentives like these, fasting has virtually disappeared from our culture, though it used to be the norm. Fortunately, it’s being rediscovered, and studies are backing up its health benefits.


Where can I get more information about fasting?

I recommend this book: The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting by Jason Fung, MD, and Jimmy Moore.

I also recommend this video as an introduction:

For more detail, check out Dr. Fung’s epic, six-part series on the science of fasting here on his YouTube channel.

And here’s a web page you can read: Intermittent Fasting–Questions and Answers.


Are you recommend that I fast?

As part of your religious duties on Ash Wednesday and Good Friday (assuming you’re Catholic), yes–unless you have a medical reason not to.

Otherwise, no, I’m not making recommendations here. I’m explaining what my experience with fasting has been and answer common questions people have asked me.

If you think fasting might be for you, great! It’s certainly helped me! But, as noted above, be sure to check with your doctor, particularly if you have medical conditions requiring things like insulin or blood pressure meds.

God bless you, and stay positive in the combox, folks!


UPDATE 1: For more on my experience with fasting, including many common questions, click here!

UPDATE 2: Here’s info on why newspaper diet advice is usually horrible, focusing on a piece in The Telegraph that completely botches the issues of “skipping breakfast,” “snacking and grazing throughout the day,” and intermittent fasting.

UPDATE 3: Snacking and Intermittent Fasting (the news is better than you might think!)

UPDATE 4: Fasting Update: The Soup and Noodles Solution

UPDATE 5: Body Fat Testing and Weight Loss Targets

UPDATE 6: Does Fasting Cause Loose Skin?

UPDATE 7: Here’s a video of me and Cy Kellett discussing the spiritual and physical aspects of fasting on Catholic Answers Live:

If you liked this post, you should join Jimmy's Secret Information Club to get more great info!

What is the Secret Information Club?I value your email privacy


Nick December 22, 2016 at 7:25 pm

“Fasting without prayer is called dieting.”
~Matthew Kelly

Thanks for this post!

Scott Leopold December 22, 2016 at 7:37 pm

Great job, Jimmy. I’ve lost 155 lbs over the last 9 months and also just downgraded to L’s for the first time in over 20 years. After a bit of research I considered intermittent fasting but decided on a program through my insurance provider instead. I still fast every Friday (Catholic-style fasting) and have considered incorporating some intermittent fasting, but what I’m doing currently has worked out well (high fiber, lots of lean protein, some healthy fats, 1100-1200 calories/day and at least 10K steps/day). Keep up the great work!

Tim Lambert December 22, 2016 at 9:56 pm

Jimmy is completely right. I have struggled with weight loss for the past 15 years. I was regularly doing the ‘eat less /work out more’ routine. But I could never keep up with it eventually I always crashed and went back to binge eating. Intermittent fasting has made all the difference in the past year, for the past year I’ve been able to consistently keep off 25 to 30 pounds. Over the past 15 years with the method of ‘less calories/more working out’, I was never able to consistently keep the weight off. Eating smaller meals with less calories never worked for me in the long run. But with intermittent fasting it’s something that has made a noticeable impact on my health, on my weight, and my ability to stick with it. I really can’t speak highly enough about it I’m not saying everyone should do it but all I can say for me I’ve never had this much success in the past 15 years.

Tim Lambert December 22, 2016 at 10:01 pm

Hi Jimmy, I just have one question for you also. Did you ever get headaches when you would first start the low-carb high-fat diet, or the intermittent fasting?
For the most part I do really well with it, but I’ll still slip up at times and binge eat. Thankfully those moments of binge eating don’t stores much weight on me is that used to since I typically go back to the intermittent fasting in a couple of days. But I will get pretty bad headaches when I making that transition from binging to fasting. The headaches leave after 1 to 2 days and then I’m perfectly fine. Same with as you said, my mind is much clearer as well as much calmer.

I guess binge eating is bad anyway. Just curious if you’d ever get the headaches.

Betty Calagoure December 23, 2016 at 3:28 am

I have 2 questions:
1) Don’t you miss food?
2) How will you adjust your eating when you reach your goal weight?

Jimmy Akin December 27, 2016 at 11:53 am

I miss food a little, but really not that much. I’m much more excited to be losing weight.

When I reach my weight goals I will stop fasting, except as necessary to maintain my new weight or for other health benefits.

Dave Awbrey December 23, 2016 at 5:43 am

Great job Jimmy! You look great! Thanks for sharing this great information.

Kenneth Heck December 23, 2016 at 5:46 am

Since judgment begins at the house of God, Catholics should be leading the weight loss campaign for America. Keep up the good work Jimmy.

Mike doyle December 23, 2016 at 6:26 am

Spiritual benefits? Might be a good companion article?

Joseph Pinedo December 23, 2016 at 8:19 am

Congratulations Jimmy, I too have tried fasting . Like you shared fasting is surprisingly easy. Jason Fung and Jimmy Moore are great resources fro more information on fasting. Merry Christmas and Happy

Karen Heiby December 23, 2016 at 9:19 am

Great post! I think I’ll get that book! Congrats on your successes, Jimmy! 😀

JohnE December 23, 2016 at 9:45 am

I’ve heard of intermittent fasting and have been thinking about giving it a try. Thank you for the info, and I look forward to hearing more. My concerns that have held me back are mostly social/cultural, such as eating meals with my family or occasionally going out to lunch with coworkers that would make intermittent fasting a challenge to implement.

I’m curious.

Karen Heiby December 23, 2016 at 9:54 am

Thanks for this! I might get that book! Congratulations on your successes, Jimmy! 😀

Nonna Rosie December 23, 2016 at 11:40 am

I was on the same intermittent fasting routine for a year or so and lost a lot of weight. Now I still eat one meal a day except for special occasions such as brunch with friends, but I’ve added coffee with cream and sugar back into my diet during the day and a glass or two of wine with dinner. I’ve maintained my weight loss for four years.

When my doctor first suggested this fast, I was skeptical. But it’s easy to do once you get into the routine, and I’m healthier now than I was before.

Peter d'Aoust December 23, 2016 at 12:51 pm

This is kind of exciting. But I guess I can’t call you Gimli Akin any more!

Dave Deaton December 23, 2016 at 5:21 pm

Great article! Thank you for posting it. I was wondering, are you also eating a Keto diet? Are you usually in Ketosis?
God Bless,

John December 23, 2016 at 8:13 pm

Have you looked into the 16:8 method of fasting? You might want to try it if you’re thinking about integrating it long term. It’s helped me immensely.

Terri lynn December 23, 2016 at 8:19 pm

A lot of hunger just comes from acid in the stomach. If you drink hot water with a teaspoon of apple cider vinegar every morning it really quenches your hunger, A lot of hunger just comes from acid in the stomach. If you drink hot water with a teaspoon of apple cider vinegar every morning it really does away with feeling hungry. If you had digestion or acid reflex problems they will disappear, also. You can put a little honey in it too.

Bruce Meier December 23, 2016 at 9:52 pm

I am really impressed Jimmy. I really need encouragement to even try. You can even see your shoes now. Thanks for the pic

Jonathan Walz December 27, 2016 at 8:11 am

Thank you very much for posting this information Jimmy! I have been really enjoying reading/watching the material from Dr. Fung. Congratulations on all of the progress you have made!

mosetsanagape December 28, 2016 at 12:58 am

you look good Jim. do not go back to the old weight congratulations!!

Kim Neal January 2, 2017 at 9:01 am

Jimmy, thanks for the info! Something I have been considering!!

Irksome1 January 2, 2017 at 2:47 pm

His is fascinating. How would fasting work with an increased level of activity?

Jimmy Akin January 3, 2017 at 12:56 pm

It hasn’t been any problem! Once your body switches into fat burning metabolism, it *has* a source of fuel to use, and exercise is not a problem. I do very vigorous exercise while fasting, and it’s not a problem!

Irksome1 January 2, 2017 at 2:48 pm

his is fascinating. ow would fasting work with an increased activity level?

Terrye Newkirk January 3, 2017 at 9:56 am

Although I am a Type 1 diabetic, I naturally eat only 2 meals a day. Eating *nothing* gets me into trouble. Even bread and water didn’t work.

So my question is, do you keep the same meal plan on days of fast like Ash Wednesday, or do you further restrict?iIcould try one meal a day, which I have accidentally done before.

I am trying to add more sacrifice. Drinking coffee black would do it. ?

Jimmy Akin January 3, 2017 at 1:03 pm

I haven’t fully researched Intermittent Fasting for those with type 1 diabetes, but I know that some folks with type 1 do it.

A thought occurs to me that using water and something high fat without significant carbs or protein (i.e., not bread) might work better. As you know, carbs have a significant impact on blood sugar. Protein has less of an impact, and fat has very little.

Perhaps something like macadamia nuts (high fat, high fiber, low carbs, low protein) might work better.

In terms of special fasting days (Ash Wednesday, Good Friday), it would be legitimate to do one’s normal fast–but to do with with added spiritual intent on those days.

If one’s health allows a stricter fast on those days, it would also be legitimate and praiseworthy to observe a stricter fast or to add additional forms of abstinence (e.g., giving something additional up on those days).

As a type 1 diabetic, though, you are excused from the fasting requirement altogether, as are all people who have reached the age of 59.

Hope this helps!

yvonne nihart January 3, 2017 at 12:24 pm

Jimmy, I have followed you for a long time now. I am 70, a diabetic and being treated for high blood pressure. I currently eat one meal a day. It is low carb, but I find myself dizzy and am not sure weather it is b/p or to much diabetic meds. So far I have dropped from 220 down to 155, but would like to get back to 100 pounds. I am only 5 foot tall and also have a really bad back. I am afraid to go no carb because of the diabetes. Any suggestions.

Jimmy Akin January 3, 2017 at 1:18 pm

From the reading I have done, if dizziness ensues, it may be that your blood pressure is dropped and that you now need *less* blood pressure medicine (a good thing!).

Check with your doctor to see if you need to lower your blood pressure medicine.

As far as going no-carb, this should be no problem if you have type 2 diabetes.

If you have type 1, I am less sure about that, as I haven’t fully researched that, however there is no such thing as an “essential carb” (the way there *are* essential fats and essential proteins–things that our body cannot make and thus that we must eat). Unless type 1 would prevent someone’s body from being able to manufacture glucose (via neoglucogenesis), eliminating carbs from one’s diet should not be dangerous.

You may want to refer your doctor to some material by Dr. Jason Fung, who has written and spoken extensively on this subject.

In particular, you may want to point your doctor to this video:

I might also add that if you are doing intermittent fasting then it is less important to restrict carbs, though it would generally still be good to do so for a person with diabetes/insulin resistance.

Hope this helps, and God bless you!

C. McCoy January 4, 2017 at 2:28 pm

So the term “Intermittent Fasting” doesn’t mean I go for X-number of days not eating anything at all, but that I try to go most of the day not eating? And you do this every day until you’ve lost the weight you want to lose?

I actually have gotten into what I thought was an unhealthy habit of not wanting breakfast and eating lunch somewhere around 3pm. Today I forced myself to have some crackers and peanut butter with an apple. I do get woozy by around 6:30 when we normally have dinner. But here’s the thing: I think I’m gaining weight rather than losing it. I will admit that I don’t THINK I’m eating more than I normally would at dinner, but for some reason, eating actually seems to make me hungrier, and after dinner I want to start snacking–toast, cookies, popcorn, etc.

So do I just have to make sure dinner is smaller–or eat my normal dinner and leave off the dessert and snacks that usually follow?

Thanks for your help. I’m really desperate to lose 40-50lbs for various health reasons and I’ve prayed a lot about it. Hoping it’s God who led me to your site.

The Masked Chicken January 6, 2017 at 7:57 am

I have been keeping track of the science of calorie-restricted diets for a fairly long time. Although Dr. Fung is a great evangelist for the practice of intermittent fasting (IF), a better expert is Dr. Mark Mattson, chief of the Laboratory of Neuroscience at the National Institute on Aging and a professor in neuroscience at John Hopkins (look for his TED talk on YouTube). He has been doing mouse studies and a few human studies on the effects of ketogenic diets with regards to their protective abilities on the neurons of the brain. These sorts of calorie-restricted diets seem to slow down the formation of tau-protein tangles seen in Alzheimer’s disease.

When the body is low on glucose, such as occurs during calorie-restricted dieting, it can synthesize more via gluconeogenesis from fats. This uses up oxalacetate, which is used in the Kreb cycle, so Acetyl-CoA is converted, instead, into ketone bodies. The body can, also, use proteins, as well, via a process called transamination. In both these cases, so-called, ketone bodies are created. A ketone is a class of organic compounds with the structural form R1-C=O-R2, where R is any carbon containing organic groups. It is formed by the oxidation of secondary alcohols. In transamination, three ketone bodies are generated:

Acetone (Ethyl ketone or ethanone)

These are very high energy fuel sources and are used particularly by the brain as fuel during famine.

Mattson thinks that the mild stress from fasting causes a stress response in the brain to protect itself. This protection seems to prevent neurodegradation.

Another aspect of calorie-restricted diets is that they help regulate insulin and promote anti-inflammatory responses, which have been implicated in neurodegenerative and heart diseases. Also, because of the longer periods of not eating, autophage, the destruction of cells with miscoded DNA, seems to be ramped up, so there is some tentative evidence that these diets will protect against mutations that can cause anything from cancer to protein misfolding (a pre-cursor to the plaque seen in Alzheimer’s disease).

We have good science on calorie-restriction in animals, but less good science in human studies, in part, because of the fear of triggering anorexia in some people. Calorie-restriction seems to increase the life-span in many animals, but it is uncertain with regards to higher mammals. Two trials on monkeys resulted in different outcomes.

The other thing to note is that there seems to be a difference in glucose metabolism during fasting for males and females. At least this is reported in the body-building community, where IF has become very popular. One must guard against the encroachment of fadism, as can happen with any type of diet.

What one eats when one is eating is also important. A recent study of 700 Scotsmen showed that the Mediterranean type diet resulted in a 30% less loss of brain density in the preFrontal Cortex in men over 70 compared to those who ate a regular diet.

Finally, IF and other calorie-restricted diets actually produce many more ketone bodies than through high fat, low carb Adkins-type diets. The Adkins diet is a ketogenic diet, but IF produces more ketone bodies, so the cost-benefit ratio is higher. These types of ketogenic diets also have one really interesting property – they seem to shut down seizure behavior. The Adkins diet is a last resort for people with epilepsy that cannot be controlled by medication. It does work in many cases. Calorie-restricted diets, whether the leangains (8-16 diet), the 5-2 diet, the Worrier diet (4-18 diet), or 1200 calorie diet may also help with seizure-control.

There is both a wealth of studies and a dearth of studies on this subject. There is not enough room to cite them, but Mattson and Fung are good places to start.

The Chicken

Bruce Meier January 11, 2017 at 8:05 pm

You & Dr Fung convinced me ,I’m into my 4th day of total fast.Am TYPE II. B .I’ve got to get down fr 228#s to 180#s. Am 77 & can hardly walk to end of driveway.Hunger is not a problem and blood sugars are falling in line 116 to 135. Last week they were 35 to 300.Next Sunday will go on 42 hour Fasting Protocol.Am losing 3 #s day right now.Thank Jimmy for the umph to get me going.
How about some prayers for me too. God bless you.

Jimmy Akin January 12, 2017 at 8:08 pm

I will pray for you! Please pray for me, too! Good job, and good luck!

Carl January 19, 2017 at 7:57 am

Really happy for you Jimmy!!

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