Wednesday, April 6, 2011

Intermittent Fasting Good, But Don't Do It Yet? The Expert Double-Bind Strikes Again

Science Daily saw fit to reprint a EurekAlert announcing that a "Study finds routine periodic fasting is good for your health, and your heart."  The article describes research done by a team apparently led by Dr. Benjamin Horne, PhD, MPH.  The team had some people fast for 24 hours and recorded the changes in the participants blood levels of cholesterol and hormones.  

They found that during the fasting period, blood levels of both LDL and HDL increased.   According to the article, Dr. Horne explains the findings this way:

"Fasting causes hunger or stress. In response, the body releases more cholesterol, allowing it to utilize fat as a source of fuel, instead of glucose. This decreases the number of fat cells in the body," says Dr. Horne. "This is important because the fewer fat cells a body has, the less likely it will experience insulin resistance, or diabetes."
I agree with the first sentence, but I doubt the second.  I know of no way that elevations of blood cholesterol influence cells' fuel use.  If what he says was true,  high serum cholesterol would indicate a metabolism that burns fat in preference to glucose, and raising cholesterol would treat obesity.

Assuming Dr. Horne actually said this, I think he has cause and effect confused.  When fasting, the body releases fat from adipose for use as fuel, and cholesterol gets released from those tissues at the same time.

Dr. Horne, I suggest that you get a copy of Eat Stop Eat by Brad Pilon if you want to learn how fasting works, or at least consult a standard physiology textbook.  ESE has an extensive bibliography referring to dozens of studies of the effects of fasting.  You will find that the textbooks and numerous research papers tell us that fasting lowers insulin, and the reduction of insulin allows the body to use greater amounts of fat as a fuel.

Next he says that this process "decreases the number of fat cells in the body."  Wow!  I have never seen any evidence that any method short of surgical excision (lipectomy) can reduce the number of fat cells in the body.  So far as I know, fasting or dieting can reduce the amount of fat stored in the fat cells we have, but not the number of fat cells.   Dr. Horne,  if you have evidence that fasting can reduce the number of fat cells, I sure would like to see it.

Horne's team also confirmed previous research showing that fasting has profound effects on human growth hormone (HGH) secretion.  Increased HGH protects muscle mass and increases fat metabolism.  Horne's research found that "During the 24-hour fasting periods, HGH increased an average of 1,300 percent in women, and nearly 2,000 percent in men."

So this fasting thing sounds pretty good, eh?  Don't get carried away:

While the results were surprising to researchers, it's not time to start a fasting diet just yet. It will take more studies like these to fully determine the body's reaction to fasting and its effect on human health. Dr. Horne believes that fasting could one day be prescribed as a treatment for preventing diabetes and coronary heart disease.
I suppose they want to cover their bases, but this kind of "disclaimer" gets my goat.  These people seem like hypercautious nannies wanting everyone to stay "safe," as if going without eating for 24 hours was some unprecedented adventure into dangerous, uncharted territory.  My cynical part read it this way:  "Look, this fasting thing could do awesome things for your health, even prevent diabetes or heart disease, but now that you know that, we want you to go back to sleep.  After all, we wouldn't want to discourage the use of drugs...." 

In nature, most carnivores or omnivores spend a lot of time without food.  Without refrigerators and convenience stores, if you want to eat, you have to hunt, and hunting takes time.  As a result, most non-human carnivores spend a far greater portion of their lives in the fasted than the fed state. 

Ethnographic records also indicate that most hunter-gatherer tribes have traditionally eat only one or at most two main meals daily, in late afternoon or early evening, which means that the people fast at least 16 hours and often 20-24 hours almost daily.  We can surmise that our paleolithic ancestors also spent far more time in the fasting than in the fed state.  Thus, rather than having to justify intermittent fasting,  which occurs as a matter of course in natural circumstances, advocates of eating more frequently need to prove the safety of frequent feeding, because it departs from the paleolithic default.

I fast 16-17 hours almost every day of the week and usually have at least one fast lasting at least 20 hours once weekly.  I almost always do my heavy and light training after at least 16 hours of fasting.  I've been doing this for more than two years with only  positive results.  I highly recommend it for weight management and health enhancement.  Don't let the nannies discourage you from doing something absolutely natural. 


Alan said...

he's a researcher. He only gets paid his salary if there's new research to do. If you told him that the Moon is the Earth's satellite, he'd say that it's possible, but more research needs to be done.

George said...

Thanks Don! I've just started IFing and, simply put, love it!

Feeling great and leaning up! I just wish I hadn't "grazed" for so many "lost" years(sigh).


Anonymous said...

When I read that report I had exactly the same thoughts, Don. The cynic in me suggests that, rather than encourage people undertake their own free & easy solution that we need to wait for more research to find a pharmaceutical approach that achieves the same result without us having to cut back on our consumption. I couldn't imagine anything worse for the food industry than people not eating fullstop.

trogdor said...

Wait, you fast 16-17 hours most days? So, when you do eat, do you get the equivalent of 3 standards meal in terms of nutrition? That seems like an awful lot to consume in one sitting.

Don said...


Yes. I eat two meals, typically at 10 or 11 am and 3 or 4 pm. I consume about 2500 calories daily, usually all of it in those two meals, although sometimes I have a snack at say 1 pm. So I fast from about 4 or 5 pm until 10 or 11a.m., giving me 16-18 hours of fasting.

woly said...

Did you find any information about how the study actually showed that it improves cardiovascular function? The title of their press release said they found it to be heart healthy but all I can see is that it raised cholesterol levels.

1leone said...

Hi Don,
I've been doing intermittent fasting now for about 4/5 months, and also train fasted. I've also had to give up grains and dairy roughly at the same time. My total cholesterol is now shooting up. Prior to fast total cholesterol was 187, now 240. HDL prior 55, now 62 and TRIGs prior 40, now 53 (all in mg/dl)
I'm very lean (<10% BF) at 72kg 6'1" Feel absolutely great and strength increasing constantly at the gym.

So is this a cause for concern or a consequence to IFiing and/or change in diet as my body readapts?

I really appreciate any thoughts & suggestions you may have,

douglis said...

So is fasting good for the heart and why?The 14% raise in LDL has confused me.

Marc said...

Hi Don,

Fantastic post as always.

1. Do you pretty much eat like that everyday? Just the 2 meals with a 16-18 hour fast?

2. I'm very curious about this question as no-one seems to talk about it (pehaps because its completely irrelevant lol)
Is there an optimal food to break your fast with?

About once a week or so my fast is longer due to work. ie; 1 large meal around 12:30 pm and nothing else until the next morning.

What do you think?

Thank you for all your insightful posts, I continue to learn a lot from you.

Marc said...

Sorry for the second comment as I just thought about it...I will do a post on the second question and see what comes back with comments.


O'Brien said...

What would you say about children and fasting? We have a 2.5 yr old that eats really well. She mainly snacks in the afternoon as she gets hungry before dinner.

Don said...


The team had previously shown that people who fast periodically have a lower incidence of heart disease. Fasting lowers insulin, and reduces platelet aggregation and inflammation, which in turn reduces heart disease.


Your HDL went up and is greater than your triglycerides, which means you have virtually no risks of heart disease. The rise in total cholesterol is transient due to the fasting; and, since your Trigs are so low and HDL higher, we can predict that your LDL is the large fluffy harmless type. If I were you, I wouldn't change anything. Check blood lipids again in 6 months or so. They don't really mean much. As long as your blood sugar and insulin are low, you are in safe territory.


see above answer to woly. The rise in LDL does NOT increase heart disease risk. Fasting will transiently raise the large fluffy type of LDL that is harmless.


Yes, probably at least 90% of days. I break my fast with a full meal of meat, fat, sometimes eggs, vegetables, fruits. I think your longer fast is a good practice.


I think children should eat when hungry and not when not (just like adults). If she's fine without food until afternoon, eats well at her meal(s), and is vigorous and gaining weight as she should, she's fine. Don't fix if not broken.

I think that probably a lot of childhood illness could be avoided if parents didn't get them habituated to eating frequently, which can depress the immune system and weaken digestion. As I understand hunter-gatherer practices, after weaning children ate no more frequently than adults.

Dana Seilhan said...

trogdor: When I stopped to think about it I could not understand why people call plant foods "nutrient-dense." The sheer amount of material you have to eat to get anything out of most plant foods... it's insane. On a lower-carb, less-plants, more-animal-foods, higher-fat diet? The volume of food you need is far less. 2500 calories' worth of salads is a hell of a lot of food, you'd be sick of eating by the time you got halfway through. 2500 calories' worth of mostly animal foods, especially the fat? No problem. Couple of smallish meals will do it.

42 said...

I find myself eating only one meal a day lately, in the evening, typically a large fatty cut of beef and a salad or veg. That keeps me going. If I feel hungry before then I'll have some salami and cheese, typically no more than a few ounces. Bodyfat percentage hasn't changed, grr.

Coast Spa Girl said...

A interesting read. I have only just undertaken IF myself, after having read ESE and
I have to say, I was still a little dubious going in, despite the copious amount of proof offered on the leangains site. Go 16 hours without eating? Really?! Now, after having dived in with both feet, the only thing that surprises me still, was how thoroughly I had been conditioned to eat, eat, eat throughout the day and evening. I absolutely do not need it! I feel great! My weight training has not been compromised at all. I can still eat big meals, and then, give my body a 16 - 18 hour break. None of this will be news to most here I know. So put my rant down to newbie experience! Lol.
Don, your observation on the eating habits of our ancestors also struck a strong chord with me.

JLL said...

Hah, the claim that fasting reduces the number of fat cells had me scratching my head too. I think the current concensus is that the amount of fat cells can only be increased.


Chris said...

I cant handle more than the occasional 14 hour fast.I lose weight and sometimes get stomach pain trying to eat enough calories on the rebound.I'm already thin and need over 3,000 per day.Haven't been able to make it work for me yet.

Russell said...

I started a 16/8 IF protocol almost four weeks ago. I was stuck around 11-12% BF for the longest time. Now I am at 9.5% with only 1.5% to go. It works! I vary my intake daily, with higher carbs postworkout. Lower calories/carbs on rest days.

Dr. Curmudgeon Gee said...

this reminds me of a study of ketogenic diet for autistic children (or epilepsy?).

anyway, the conclusion is
the researchers are trying to develop a "drug to put patients in ketosis" without all the "harmful SFA" (from coconut oil/MCT). uh!


trogdor said...

@Dana- I'm definitely finding myself less hungry after cutting most carbs out of my diet and eating more meat/eggs/salads. Especially in the morning- waking up to bacon and eggs is so much more satisfying and tasty than waking up to oatmeal ever was.

Valda Redfern said...

I generally have only one large meal a day on weekdays, starting at about 20:00 or 21:00, meaning that I typically fast for about 21 hours. I've been doing this for nearly a year, not from policy, but simply because I find it convenient - I don't bother with breakfast or lunch during the week, and I don't miss them. At weekends I have brunch at about 11:00 and supper at the usual time, ie only nine or ten hours between meals. This regime doesn't seem to have affected my weight one way or the other, but I like knowing that I'm not going to expire from inanition if I skip a meal or three.

Anonymous said...


Your pattern is typically how I work: train clients from 6am to 1pm, come home and eat some eggs, sausage, and nuts. Later, eat more meat, blueberries, wine, etc. etc. Leaner than ever, good strength.

As you know, once you get "it" it's no big deal.


Anonymous said...

I also IF everyday (from the past months) for 15-17 hours, and at least once a week I do a 18-20 hours fasting. I eat two big meals with 1 or two snacks. It's great. I am lean and muscles showing! LOL!

Have anyone notice that while on the Primal/Paleo way of eating, you experience less hunger (assuming you are eating lots of fat), and thus "fasting" comes naturally?

Don said...


Thanks. I liked your post on your training history, can relate. I just had another training precision epiphany this week, partly due to adapting my training to an injury. Your post coincidentally helped me realize I needed to refine my approach.


I have had the same experience.

Dr. Curmudgeon Gee said...

Hi, Dana,

last weekend i went to Whole Foods.

the bag has a list of "most nutrient dense food" probably due to the partnemship with Dr. Fuhrman.

i think they're only counting the calories.

i agree that if you count by volume, plants are nothing but "nutrtient dense". one has to either eat an insane amount, or spend too much time eating; not to mention a lot of nutrients are unavailable to us.