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Metabolic Effects of Alternate Day Fasting (in Rats)

sharma-obesity-rat1Alternate day fasting has been proposed by some as an effective (if slightly impractical) way to control body weight.

Now a study by Kazuhiko Higashida from Waseda University in Japan, published in Life Sciences, suggests that the metabolic effects of this approach may not be quite what one expects.

The researchers examined three groups of rats, one with free access to high-fat chow, one with alternate day free access to high-fat chow and one with free access to regular chow.

Although both high-fat groups gained more weight that the normal chow group, the alternate high-fat rats gained less abdominal fat than the every day high-fat group.

However, both the alternate-day and every day rats became insulin resistant with the alternate day fed rats having about 42% lower glucose transporter protein in their muscle compared to the regular chow rats while the every day high-fat rats only had a 30% decrease.

Thus, although alternate-day fasting may cause less accumulation of abdominal fat, there were no metabolic differences between the two high fat groups – if anything, glucose metabolism tended to be worse in the alternate day rats.

The reasons for this discrepancy are unclear and it will be interesting to see why the alternative day fasted rats did not benefit metabolically from gaining less fat.

I am not aware of similar findings in humans but it is certainly an issue that warrants study given that alternate day fasting is being promoted by some as a strategy to control you weight – perhaps not such a great strategy if glucose metabolism does not improve.

Edmonton, AB

ResearchBlogging.orgHigashida K, Fujimoto E, Higuchi M, & Terada S (2013). Effects of alternate-day fasting on high-fat diet-induced insulin resistance in rat skeletal muscle. Life sciences, 93 (5-6), 208-13 PMID: 23782997




  1. While I often question some of the negativity and hopelessness on this blog, I have to say that my practical personal experience with alternative day fasting hasn’t been positive. The idea of eating 500 calories a day on an alternative day schedule made me cranky, moody and generally dysfunctional on those days I was fasting.

    I have one general rule that governs any practice concerning diet or exercise. Only do what you can reasonably do forever. This practice doesn’t pass this threshold of reasonability.

    Everybody is looking for a shortcut or a trick, but the mechanics of weight loss are simple, although not always easy.

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  2. I find these results interesting and semi-applicable to an experiment I’m running on myself. I am trying to manage a re-loss. Currently, I have re-lost 7 pounds from a 21-pound regain (which happened over the course of a decade). I am currently 54 pounds down from highest established weight. When I began my experiment I was at negative 47 pounds from highest established weight.

    Over this summer I have gone to a system of check boxes — eight per week. At least one per week must be “VLC” or very low calorie day. That would, for me, represent a day of 1,500 or fewer calories. The other days may be 1,800 calories, give or take 200 (my normal intake). The other seven check boxes may be days with an exercise unit (50 minutes of sweat) or VLC days. So, with eight check boxes I have at least one overlap day: A VLC day in which I exercise.

    I find I cannot have two VLCs in a row (even if one is a low-key, non-exercise day) because I will have sleep disturbances, concentration issues and other problems that either accompany or lead to “eat impulses” or even gnawing, insulin-triggered hunger. To have a VLC, I generally cut 300 carb calories, not fat calories, because fat calories keep hunger at bay.

    At any rate, it seems to be working. Over the summer I have re-lost 7 pounds. I know that you appreciate how difficult that is, but most people (who are attuned to Biggest Loser type losses) would think that pretty paltry.

    My take away from the rats, comparing them to me: Alternating restriction days need not be full-out fasts, and it’s probably better for insulin function that they not be. Moreover, to me that kind of extreme restriction for a whole day at a time would not only lead to insulin-processing consequences (as per the rats), but the fast days would interfere with my ability to sleep, to focus and to get my work done. Rats don’t have to work. No one expects them to be competent at anything, and nobody cares if they have bad night’s sleep.

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  3. This examines a high fat diet every other day, but not simply eating every other day. Was there a group that received a control diet (regular rat chow diet; low fat diet) every other day?

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  4. These findings leave too much open to have any significant conclusion except don’t eat a high fat diet, ADF or not.

    I’ve been doing two 24 hour periods per week and have seen excellent weight loss (2-3 pounds per week – down 11 pounds now). Never a day without food. Eat Monday evening meal around 5pm, don’t eat until 5 pm Tuesday. Do the same on Thursday and Friday. This is incredibly easy to do and cannot see why I wouldn’t be able to do this for the rest of my life.

    Same food, no restrictions (except gorging because I think I can for the deficit I created) just two 24hr periods per week – any two days – or one if the situation doesn’t permit.

    I don’t understand how this study applies to any diet I know of.

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  5. What is the consensus on intermittent fasting? As I understand it, these are not full-day fasts, but going without food for perhaps 16 hours. (This is easiest to do overnight.)

    I am a Muslim, and I can tell you that fasting from sunrise to sunset for 30 days (during Ramadan) does not typically lead to weight loss. Of course this could be because many people make up for not eating all day by eating a hearty (and often late) evening meal!

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  6. The results from this study are bogus. I’ve read the study and they fail to specify exactly what the feed is. They claim it’s high fat. Yea, high fat and what else? Low protein? Low carb? High protein? High carb? The fact that insulin resistance occurred automatically points out that they were feeding the rats a high carb diet along with a high fat diet which would cause this sort of fat gain paired with this level of insulin resistance. This is because a very low carb, high fat diet has been shown over and over and over again to result in insulin sensitivity due to the body being in a low insulin environment.

    So yea, this study is bogus and can’t be taken seriously.

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