April 14, 2008

Intermittent Fasting: A Cranky Fitness Primer

[By Crabby]

Mmm, Nothing Beats The Fresh Crisp Taste of Air!

We at Cranky Fitness endeavor to stay at the cutting edge of nutrition and health reporting, except when we can't be bothered.

But we can't help noticing that Intermittent Fasting is becoming a hot topic. So it seems a good time to try to scrounge up a few extra google hits bring readers up to date on this important new research development!

So here is it is: a Cranky Fitness Q & A, telling you Everything You Ever Wanted to Know About Intermittent Fasting, Unless It's Kind Of A Hard Question.

Q: What is Intermittent Fasting?

A: "Intermittent Fasting" means: Not Eating (yikes!)-- But Only Sometimes (whew!)

Q: Sounds Unpleasant. Why in the World Would I Want to Do That?

A: Because research suggests that intermittent fasting may have health benefits. This seems to be true even if you go back and scarf up all the calories you missed out on once you go back to eating. And this technique works particularly well if you're a mouse! (Most of the studies are still animal-based).

Also, there is plenty of research suggesting that people on long-term calorie restricted diets see improvements in health and longevity. But then who wants to face the prospect of nearly starving yourself every day for the rest of your very long, long, long, long life? Intermittent Fasting is, at least theoretically, a way to get some of those Calorie Restriction benefits while still getting to pig out every now and then.

Two good but somewhat conflicting sources of information on this are: Mark's Daily Apple, which gives handy and rather optimistic suggestions on how to do IF, and an article by Alan Aragon, who has brought together a lot of research on the subject and is perhaps not quite so optimistic.

(Note: we love Mark's Daily Apple, but they are much more Hardcore Healthy over there than we are, so we shall be poking gratuitous fun at them. They are always so darn cheerful about eating their junkfood-free diets. Where's the whining? Anyway, Mark fans, be forewarned).

Q: What Are Some of these Great Health Benefits From Fasting?

A: Glad you asked! If the animal stuff proves out in humans, some of the benefits could include: "decreases in blood pressure, reduction in oxidative damage to lipids, protein and DNA, improvement in insulin sensitivity and glucose uptake, as well as decreases in fat mass." (Note: summary stolen word for word from Mark. Why waste good summarizing?)

Q: Sounds Cool! So How Much Not-Eating Will I Have to Do?

A: Here's where it gets complicated. There seems to be two ways of looking at it.

The Easy Way:

This is the approach taken by the folks at Marks Daily Apple. Basically, they say: don't eat whenever you don't feel like eating. You don't have to go a whole day without eating, because, well, I don't know why not.

Along with more difficult options, they suggest the "condensed eating window," the "early and late" plan, and the "skipped meal." (They also suggest elsewhere on the blog that you should generally be trying to fuel yourself by grazing throughout the day, eating frequent meals to keep your metabolism moving. So as far as I can make out, if you're eating frequently or not eating at all, it's all good. Or all bad--it depends on your general tendency towards either smugness or guilt).

But Mark isn't the only one who suggests that skipping even single meals might bring health benefits. He's got Mark Mattson, a neuroscientist, on his side. And we hate to argue with neuroscientists because who knows, one day they might do something sneaky to our brains when we're not paying attention.

Q: So What's Wrong with Doing it The Easy Way?

A: Well, a quick glance at both the human and animals research seems to indicate a mysterious leap from studies looking at "Alternate Day" fasting to recommendations that one try "Intermittent Fasting" and skip a meal here and there. The studies that look impressive tend to be "Alternate Day" regimens that involve fasting or drastically reduced eating (i.e. 300 calories total) for an entire day, not just missing a meal now and then.

In fact, research suggests that "haphazard eating" isn't smart and that eating just one meal a day has some health downsides.

On the other hand, research for this blog post was not exactly exhaustive. (Hello, Google? Got anything on intermittent fasting?) So if anyone knows of a good study showing awesome health benefits from skipping random meals, please pass it on.

Q: Okay, So Should I Try Alternate-Day Fasting Then?

A: Sure! But watch out:

Most people who do it get really hungry.

On the other hand, many of us know people who fast periodically or who eat just one meal a day and they seem to be totally fine with it. (Weak-willed cupcake-consuming slackers like Yours Truly are not among them).

Q: This is Too Confusing! Maybe I Should Just Go Back to the Idea of Fueling My Metabolism by Eating Small Frequent Meals All Day Long?

A: Errr... maybe not!

Weirdly enough, given how many times we hear this "fueling" suggestion, according to the Aragon article there's not really much research to back it up. It looks like folks may be overgeneralizing from the Don't Skip Breakfast research. (Don't Skip Breakfast is indeed well-supported. So we're with your mother on this: don't even think about it).

Q: So then What Do You Suggest?

A: Don't skip breakfast. But then after that, do whatever the hell you want. Keep an eye on the research--or better yet, stay tuned to Cranky Fitness. If the studies get more definitive about when you should eat and when you shouldn't for optimal health, we'll let you know. That is, if we happen to be paying attention that week.

Q: Were You Aware That Reading About People Not Eating Can Make You Really Really Hungry?

A: Yes, this phenomenon has recently come to our attention! However, research indicates that a peanut butter and banana sandwich with a glass of milk will take care of the problem fairly quickly.

So have any of you folks tried fasting?

Or are you thinking about it? Cranky Fitness is too attached to frequent meals to even attempt an experiment, but we'd love to hear your thoughts or experiences.

And On an Unrelated Note:

Tomorrow is a special day for Cranky Fitness. If you're Smart Enough to figure out why, don't give it away just yet--instead, be sure to check in tomorrow for a Very Special Post!


  1. I've heard about the health benefits of fasting but I love eating too much to do it! I'm like you crabby... small intermittent meals rock. They let me eat more often. I like that. =)

  2. I personally am still skeptical. We have a saying in the biomedical research sciences regarding enhanced longevity - Do you really want to live 15 more years if they're "Depends years"? Meaning, why live longer if the quality of life is crap? There has been no research proving that humans will reap the same health benefits that mice do in the very long term. After all, mice only live about 2 years, and my great aunt is now 96.

    Anyway, I'm off to troll the primary literature and see what I can find out about this topic.

  3. monica, hooray for eating more often!

    And Gena, since I was pretty slacky on the research, please do check back if you get the chance if you find anything helpful. My head was spinning with the eat-more-often vs no, don't eat at all contradictions.

  4. ooooooh SPECIAL DAY!
    I cant wait.

    and I just wrote an article on this over the weekend (a sadder 4 words hath never been typed: working on the weekend) and can not wait to hear what your readers have to say/if they've tried it.

    my conclusion is that while it may work for some (to each her own I guess) it would make for one HUNGRY CRABBY (ha ha) MizFit.

  5. ps---did you see the NY mag (*wink* I know..I do read other things) article a WHILE about about the hardcore fasters? to live longer?

    a rose by any other name is anorexia.

    we are a strange strange society.


  6. Reading about people not eating DOES make you very hungry. I watched the youtube video KatieO over at Sister Skinny posted and could not stop thinking about food!

    Intermittent Fasting?? I almost passed out from the thought of it...

  7. Wow - I'm the first one who loves IF?? I really do too. For religious reasons, I fast for twenty-four hours once a month (yep, I'm one of those kooky Mormons the fasting study that showed the reduction in cardiovascular illness was done on!) There are many benefits for me of OCCASIONAL fasting: It makes me feel more connected to my body, it allows me to focus on other things besides food, and I actually like the hunger. Okay, I don't like feeling hungry - that sucks - but feeling true, honest-to-goodness-need-food-now hunger can be really helpful. It "resets" my hunger and helps me discern between true hunger and emotional eating (or just cravings).

    I've never been able to get into the every other day bit though. Once a month enough's for this "hardcore" girl!

    PS>MizFit - I didn't read the NY article but there is a big difference between fasting, when done properly, and anorexia.

    PPS> A common myth is that fasting helps you lose weight - it really doesn't. At least not in the long run.

  8. God gave me hunger pangs. He gave me food to eat. Therefore, when I have hunger pangs, I eat and all is right in the universe, or at least in Marijke's part of the world...

  9. Back in my misspent youth I would occasionally go a day without eating. I smoked back then so it was easier to not eat.
    I have no desire to do that now, and I no longer smoke, so it would be more difficult.
    That said, if I needed to tell someone off and wanted help working up to it I'd not eat for a while so my blood sugar would get to the required interesting level. I've never had to do this, but the option exists.

  10. Verrry Interesting. The Bag Lady fasts occasionally, unintentionally. Oh, wait, does drinking copious amounts of beer instead of supper count as fasting......?

  11. I love reports that show that I'm RIGHT and all the health nuts claiming I should be eating small frequent meals are WRONG. Wheeee! (The fact that I'm not a mouse is totally irrelevant. Totally.)
    Of course, the fact that I've been eating two Large Meals a day for many many years doesn't actually prove anything about longevity yet–I'm only 55.

    Mary Anne in Kentucky

  12. In my residency, I was so busy that I evolved into an IF style of eating. I think, like many lifestyles, we have amazing adaptive abilities. Whatever it is, it works for me, at least so far :-) I never did it to lose weight, but rather as part of a fit lifestyle to keep on keeping on! I'm with Charlotte on this! I don't try to get others to do it, as I think it's a personal choice. I just want to add, that when looking at the lifestyle choices that 95% of the people I know make, this seems to give a much better result.

    Dr. J

  13. I think, for every study showing the benefits if Intermittent Fasting, you can probably find 3 other studies debunking it. At first, I thought the article was about "Intermittent Farting" of which I do all the time and completely recommend.

  14. "A: Yes, this phenomenon has recently come to our attention! However, research indicates that a peanut butter and banana sandwich with a glass of milk will take care of the problem fairly quickly."

    Aaagh! I knew it! This whole post was a scheme to make me want to eat a PB&B and wash it down with a glass of milk! (But I don't have any PB or B at the moment and I'm lactose intolerant, so...)

    I've thought about fasting from time to time (mostly when hearing about other people doing it) and I don't know if I would have the patience for that. Even if I could manage it, I'd be chewing people's heads off! (Does head-chewing still count as fasting?)

  15. What Charlotte said. Exactly. That's me.

  16. I think IF also poses a dangerous possibility for folks who've dealt with eating disorders - I imagine it could trigger a relapse, whether we're talking anorexia or binging, and I haven't seen that caveat mentioned anywhere.

    Aside from that, though, the research is interesting. I don't feel like I'm in a place where fasting would be anything other than psychologically detrimental, but I'm filing this away for future, more-stable, reference. Curious to see if the research piles up.

    Back to my many small meals...

  17. Hiya Mizfit, I did some pushups today just for you!

    Glam, that was a fascinating video, wasn't it?

    Charlotte--"Kooky Mormons?" We love KM's at CF! For some reason, a lot of health-conscious, smart, amusing bloggers seem to be Mormons. I'm glad IF works for you even if I'm too wimpy to even think about skipping one meal, let alone a whole days worth.

    Thanks Marijke, Bag Lady and Leah--I think we're all in the same camp and need our feedings. As usual, I seem to be Canadian.

    Mary Anne--Glad you're able to get by with eating less often, and now you have some nifty research to back you up! Even if you're not a mouse.

    Dr J--I think residents must have superhuman abilities to adapt, given the eating and sleep schedules required. I could so NEVER manage to become a Doctor.

    Nitmos, Intermittent Farting, what a great idea for a post!

    Chicken Girl, sorry 'bout that! Alas, there is no cure for peanut butter cravings except for peanut butter.

    Hiya Katieo! (See reply to Charlotte above).

    Hmm, good point--I never even thought of the eating disorder angle.

  18. I once joined a friend in a fasting-for-charity church program he was doing; it was only 24 hours and by the end of it I felt awful. I was so hungry. I love the grazing.

    But, what doesn't work for one person will work for another, so I don't think that eating all day or fasting all day is really the answer at all- the most important thing is to listen to your body and do as it tells you (and right now, mine is telling me that it definitely requires a PB and banana sandwich with a glass of milk!)

  19. I think it's all down to what works for the individual. I used to do that Master Cleanse fast a few times a year, and it made me feel great. Until it didn't anymore, and I quit doing it. I would consider fasting one day a month, but I'm still not convinced that the Mormon study sufficiently ruled out all the other contributing factors that make Mormons healthier in general.

    I'm really glad to see the "several small meals" hypothesis at least partially debunked. If I don't get hungry before I sit down to a meal, I end up eating to satisfy mouth hunger, and eating too much. Through trial and error, I figured out that three square meals works best for me. It may not be interesting or cutting-edge, but it helps me keep track of what I eat and maintain a healthy weight.

  20. I don't think an every-other-day fasting would work for me very much, since when I don't eat, what I do instead is sleep. And even as a stay-at-home mom, I do need to be awake.

    That said, I think some IF is probably not a bad thing, and I've been known to skip a meal, either accidentally or on purpose from time to time.

    On the Weight Watcher's Core plan, I tend to eat when I'm hungry and don't when I'm not. I think that works best for me, but as I haven't tried EVERYTHING yet, I can't be sure.

    This requires more investigation and experience. I shall do so... if I learn anything interesting, I'll let you know.

  21. I fast intermittently! It's just that it is usually followed by the extraction of blood or some other medical procedure. Having said that, I do find that once I have fasted, I can't stuff as much in my gut and that has to be a good thing! Too bad it doesn't last much longer than a couple of meals.

  22. i'm so glad i have cranky fitness to count on -- i never have to do my own health and fitness research!

  23. I read about and even tried IF, using a one meal a day sort of set up. The mindset it put me in for most of the day reminded me so much of how I felt when I was battling anorexia during high school and early uni that I stopped pretty quick. That part of my brain certainly found the whole thing attractive for a whole lot of reasons but it scared the crap out of me for those same reasons. I'm trying four relatively equal smallish meals a day now.

  24. what an interesting article. I don't think I could do it. I fast for Lent when I am supposed to and I am dying by the end of the day. I get faint and cranky when I don't eat. I think I will stick to my small meals, but definitely an interesting idea. I guess I can't criticize my hubby for his one meal a day habits.

  25. How absolutely confusing! I think I'll stick with my breakfast in the morning and then eating as usual through the day . . . though I am making an effort to limit the cookies. That counts for something, right?!

    BTW: My kids were wondering why I was laughing so hard when I was reading your post. Your Crabby take on intermittent fasting was fabulous!

  26. When the husband and I went to Hawaii for our honeymoon I did it. But not on purpose. We were very busy during the day hiking or being island-y, so we skipped lunch. (Well for me, "skipping lunch" means eating only a Zone bar or piece of fruit.) I didn't even really notice. I never dreamed this behavior would have a big official name and all. Typically, I graze.

  27. For a couple of months I did Alternate Day Fasts. I miss the social aspects of food sometimes. It has helpped to sit at the table at dinner with just my water. Hunger? I'd feel a twinge once and a while, but the real bad end of the deal was when I started eating after a fast. I did "feel" hungery again and got stuffed and stayed stuffed. I've changed to a once a week 40 hour fast and now don't have the binge style rebounds. The longer time seems to have allowed my stomach to really shrink and I just fill up on a one sandwich lunch and can wait until dinner and easily move back to three meals a day. The mental pressure of not going on another fast for the rest of the week makes it easier too. Before I tried IF I tried grasing and just felt like I was eating all the time and I was gaining weight; now, in three months of IF I've lost three pounds; not much but its about the same pace I gained the 10 percent that I've been I've become overweight.

    I think different things are going to work for different people, and all clinical trials are going to show mixed results because they are a random selection; therefore, some are going to do well fasting and the others would be better off doing something else. Science will not reach a solution because we are too variable and the scientific method demands that people are only one thing to be tested.

  28. I recently started doing IF, with a schedule of 24 hours fasting (water only) and 24 hours eating whenever I want. I find it incredibly easy to do. I blog about it at http://eatingandfasting.blogspot.com/


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