Intermittent Fasting and/vs Calorie Restriction Diets

Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake. Anson RM1, Guo Z, de Cabo R, Iyun T, Rios M, Hagepanos A, Ingram DK, Lane MA, Mattson MP. Proc Natl Acad Sci U S A. 2003 May 13;100(10):6216-20. Epub 2003 Apr 30.

Dietary restriction has been shown to have several health benefits including increased insulin sensitivity, stress resistance, reduced morbidity, and increased life span. The mechanism remains unknown, but the need for a long-term reduction in caloric intake to achieve these benefits has been assumed. We report that when C57BL6 mice are maintained on an intermittent fasting (alternate-day fasting) dietary-restriction regimen their overall food intake is not decreased and their body weight is maintained. Nevertheless, intermittent fasting resulted in beneficial effects that met or exceeded those of caloric restriction including reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxic stress. Intermittent fasting therefore has beneficial effects on glucose regulation and neuronal resistance to injury in these mice that are independent of caloric intake.

My comments:

I have never been that interested in diet as I never had much of a problem with body weight, nor as a physical therapist did I really think it was my job to talk about it, except maybe to suggest that weight loss or gain might be beneficial for a given patient. However, since reading the paper on dietary restriction preserving muscle mass and preventing sarcopenia I have continued to read more on the subject. I had also read about the Warrior diet on wikipedia, concluded it fit my personality pretty well, not eating during the day then eating as much as you want in the evening. This week I read and finished the warrior diet book, and I thought it had some good insights but I was a bit disappointed to learn that the author did a lot of eating during the day rather than abstaining, which isn’t what I have done or wanted to do. Reading the criticisms of the Warrior Diet on a lot of people said they liked the concept but the book was padded out and he did a lot of promoting supplements which I’m not interested in either. Someone said they started off on the Warrior Diet, then moved on the the Fast 5 Diet, which it turns out is what I was already doing, didn’t promote supplements and best of all the pdf of the Fast-5 Diet book is available free. I’m not going so far as to say I’d advocate it yet, but I’m on my 15th day and so far I like it.

So what’s the point? Calorie restriction has been shown to extend the lifespan and prevent disease, and muscle loss in a wide variety of fauna, with similar metabolic improvements seen in people, though the prolonging of lifespan in humans has yet to be established. Regarding the animals, some of the caloric reductions were done by just limiting available calories 30% (plus or minus depending on the study) while other papers were limiting calories by feeding the animal every other day. This led researchers to wonder how much of the every other day diet (intermittent fasting) benefits were due to the calorie reduction, and how much of it was due to the spacing out of the food source (fasting irrespective of calorie reduction). Most of the mice on the every other day diet decreased overall calories but the strain used in this paper ate almost double on the feeding days such that overall calorie intake was about the same (~90% as the mice allowed to eat as much as they want everyday).

Both the fasting and the calorie restriction mice had reductions in blood glucose and insulin to a similar degree with a slight edge given to the fasting mice. IGF-1 and B-hydroxybutyrate however increased in the fasting mice, but went down in the calorie restricted mice with the researcher concluding these increases might be neuroprotective, as was the shift towards ketosis, found in the fasting but not calorie restrictive diets. The mice were then injected with kanic acid to their hippocampus to assess if there was an effect with either diet on neuron survival. Both the caloric restriction and intermittent fasting rats had better survival of neurons compared to the mice that ate their fill daily, with the intermittent fasting mice being significantly better.

So based on this study intermittent fasting has some health benefits in addition to and separate from what you get from calorie restriction alone (EVEN IF YOU EAT DOUBLE ON THE NON-FAST DAYS). The question then becomes, what’s the best/easiest/most tolerable form of intermittent fasting. The mice did an every other day fasting diet, which to me sounds miserable. Though, skipping breakfast and lunch per the Warrior and Fast 5 diets sounded fairly miserable to me too, until I tried it, and so far I like, and I definitely feel like I have more energy during the day. It’s still unknown, at least to me, if the once a day diet has similar protective benefits to the every other day diet. I should point out that it likely doesn’t have to be either/or proposition as these researchers had to search for a strain of mice that ate double on the feeding days because most didn’t and calorie reduction went hand in hand with intermittent fasting. Thus far I notice it does seem to reduce my overall calories too, so with the best of both worlds maybe I’ll live to 150 before I have my consciousness uploaded into a robot;) To be continued…

Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember Spinal Flow Yoga for you or someone you know in the future.

Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.

6 thoughts on “Intermittent Fasting and/vs Calorie Restriction Diets”

  1. Chad,
    We spoke briefly about this before, though reading about your findings gives additional insight to the benefits of a fasting diet over a long-term period.

    That said. I’ve read articles in the past (i’ll have to find them for you) that contradicts that type of diet IF as an individual you are trying to cut weight and speed up metabolism. Personally, i’ve always been a larger guy and cutting weight is difficult.
    I’ve seen research suggesting eating my daily caloric intake all in a small amount of time, once per day, can lead my body to react by continually storing additional fat since it is not receiving nutrition throughout the day in intervals.

    I’m still curious to compare this study to the specific needs of loosing body fat and increasing metabolism. It seems study shows that by eating small portions, every few hours throughout the day is a way to increase fat burning and metabolism overall in individuals while still preserving muscle mass. I’ll see what articles i can find to challenge or back up what i’ve learned in the past 10 years of personal experience with weight training, diets, etc.

    Good post though, I enjoy reading about alternatives to both a healthy diet/lifestyle along with additional benefits that can be achieved.

    • Thanks for the comments Jake. I hear that a lot because the many small meals is what has been taught for the last few decades or so. I wouldn’t consider myself an expert as I only became interested in the caloric restriction/intermittent fasting stuff since mid April of this year when I read and blogged on that monkey study where they found increased muscle mass from eating less as they age. But that study wasn’t about fasting, rather just caloric restriction without a time restriction. It just turned out when I was reading more of the same types of papers regarding longevity in animals that intermittent fasting did much the same even if you didn’t restrict calories, the first paper I read being the one I discuss above.

      From what I understand caloric restriction with a lot of small meals works, but regardless of diet type, they all slow your metabolism. Which isn’t necessarily a bad thing as one (of several) of the anti-aging theories with caloric restriction is that you slow your metabolism and that’s why you slow aging. To speed your metabolism, and still lose weight I would think you would want to do higher intensity interval or strength training. I, like you, had heard that by skipping meals you would break down more protein and lose muscle. However in my years of always skipping breakfast and occasionally missing I never felt like it was a problem for me but I thought maybe I was weird. Also I never looked up any of the diet relating research, but some of that old wisdom does seem contradicted by some of the newer studies being done on intermittent fasting/time restricted feeding. So my plan is to read more of the newer and older papers together to see if I can determine what’s behind the contradiction.

      The thing I really like about the intermittent fasting, unlike a lot of small meals, is that it’s so easy. In fact it’s better than easy, because it saves you time with regards to food prep and eating. There are a lot of things I notice from doing it, so after I get my blood tests next week I plan on doing a blog about my thoughts, likes and dislikes from trying it.

  2. Chad.. After doing more research into both the interval eating (around 6 meals per day, every 2-3 hours) and forms of a fasting diet, I have concluded that you may take the win on this.

    The most interesting, and backed by science, article that I found is similar to what you are going through. Though it is an 8 hour mealtime program (9am-5pm each day is ok to eat) suggesting that without limiting your intake but rather the time at which you intake calories is a drastic advantage.

    Clearly outlining benefits in both Fat Loss and lower risk to heart disease and diabetes. Clearly showing that our bodies are programmed to more or less Fast from around sun-down until about an hour after waking.

    Check it out and let me know what you think.


    • Hi again Jake. Funny you should mention the 8 hour diet because I ordered that book last week and I’m still waiting to get it. It sounds like it’s less restrictive than the Fast 5 diet that I’m doing now in that you can eat over an 8 hours instead of a 5. The other big difference is that I don’t start eating until they stop. I generally tired if I eat and I notice by staying hungry all day I feel more alert and that I have more energy. So I’ll be curious to see what the 8 hour guys have to say when to eat rather than just over how many hours. I did find a few studies that looked at diet and circadian rhythms but I haven’t had a chance to read them yet. The last fasting blog I did looking at stroke damage and recovery use an 8 hour fasting model.


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