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Switching to a rich diet unhealthy after restriction

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There is a puzzling article at https://medicalxpress.com/news/2020-02-theory-effects-diet-lifespan.html

New research challenges theory explaining the effects of diet on lifespan

If the results are confirmed in humans, it would seem to imply that intermittent fasting could be damaging to health.  I do have some questions and doubts about their results.


The theory that they challenge is that in times of reduced nutrition, the body goes into a maintenance and repair mode to await times when food is more available.  To test this they switched fruit flies from a low calorie diet to a rich diet for testing.  They report that the flies switched were “more likely to die and laid less eggs” than flies whose whole life was on a rich diet.  They also suggest “changing diet repeatedly or abruptly could be harmful to health.”  They claim their “results have now pointed us towards a more refined explanation of why it occurs” (It refers to what they call the dietary restriction paradox.

Some questions I have are

1)     How restricted was the diet?

2)     How rich was the diet?

3)     How abruptly was the switch?

4)     I did not see any explanation in the MedicalXpress article.

So, I’ll watch for confirming results in mammals before I stop dabbling with intermittent fasting.


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Hi coryboro!

The study wasn't one on intermittent fasting -- it was on dietary restriction.  I didn't find the results surprising -- it's been well-known for a long time that yo-yo dieting is harmful to health.  The quote that I find most relevant in the article was:

"The findings also suggest that changing diet repeatedly or abruptly could be harmful to health in certain situations."

(I guess that one could worry whether intermediate fasting resembles CR or yo-yo dieting.  I don't know -- but I suspect that intelligent IF -- no food one day, MODERATE eating the next day, repeating the pattern -- should probably be OK.  I attempt CR myself.)
  --  Saul

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Thanks for your comments Saul.

Today, I found this reference to the study  https://www.inverse.com/mind-body/fruit-fly-study-reveals-the-hidden-costs-of-intermittent-fasting  

which strives to warn readers about the hazards of IF even though they ran several articles last year on the benefits of IF.  Perhaps as humor, in the Dec article, they wrote “…much of that research was conducted in animal models, so the evidence that intermittent fasting holds miracle health benefits for humans is thin.” while embracing embracing the current study using fruit flies.  


Looking at the source article, I found

 rich media [8% autolyzed yeast, 13% table sugar, 6% cornmeal, 1% agar, and nipagin 0.225% (w/v)]

restricted media (2% autolyzed yeast)

To my untrained eye, it looks like they were abruptly shifted by 75% (2% vs 8% autolyzed yeast).

 IIRC, a 75% restriction is generally short lived.  Also, abrupt changes are not good.  I’d say they successfully confirmed the rationale for the Minnesota Starvation Experiment.


As you noted, the article has little relevance to sensible restriction and IF.  I apologize for wasting bandwidth on it.

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