Hi Reason & Fight Aging readers,

In my previous writing, I regret the use of "my work".

All authors on the FASEB paper contributed to this work.

All the authors, except me, are well-known and have contributed to the field of aging research in many different ways.

So, this Housefly CR effort is actually "our work".

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The implications of the housefly CR research are something that should be addressed.

It is intuitive to me that food dilution is not the same as calorie restriction. We may soon have data to support this.

Your statement:

"On the other hand, if it were the case that fruit flies benefit from CR while houseflies do not ... well, that would seem to be a difference
worth investigating more closely. Pinning down the biochemical and genetic roots of CR will have long term benefits for our health and longevity - hence all this careful work with flies."

Reason, I think you are right-on.

Obviously there are many things about CR that are not well understood. There is clearly a disconnect regarding CR in Houseflies and CR in Drosophila. The CR researchers working with Drosophila have important questions to consider.

I am continuing work in this area also.

Thanks Reason,
Mike

[Posted by: Michael Cooper at November 16, 2004 2:47 PM]

Michael, quick question, since I only see the abstract.

I understand that you (a collective you I suppose) were able to directly measure food intake, thus ensuring an accurate measure of the degree of CR.

However, beyond that better system of control (relative to the Drosophila studies), I was wondering about other aspects of the experiment(s). At what stage was CR initiated, and was it a gradual decline in calories, or was it sudden-onset CR? I've seen studies in mice where CR did not benefit the mice, but the method of CR can sometimes be as critical as the presense of CR.

Also, one final point: Even if CR wasn't measured accurately in drosophila experiments, we at least know that *something* was increasing longevity in those experiments. So this doesn't invalidate the idea that something in diet is responsible, it only only casts doubt on the numerical correlation of degree of CR with longevity.

[Posted by: Jay Fox at November 17, 2004 7:59 AM]

Interesting comments, Jay.

As you might expect, houseflies can be fed in separate containers; solid food and water.

CR was initiated on the fourth day after the flies eclosed (hatched). For some groups of flies the decline in available calories was gradual, for other groups not so gradual. The flies were restricted at 100%, 90%, 80%, 70%, 60% and 50% of average consumption, measured in the first four days. Fully-fed (ad libitum) flies were used as controls, this group had the longest mean survival time. The flies restricted at 50% died rather quickly, probably due to starvation. Other groups of flies had progressively shorter survival times as the severity of caloric restriction increased. Other experiments indicate that houseflies do not possess physiological mechanisms that permit adaptation to decreased calorie intake.

Experiments in houseflies were performed with widely varying diets to optimize survival time. So, yes, the diet does affect the lifespan of houseflies.

Typical feeding of Drosophila is such that they obtain everything, including water, from their semi-solid food mixture.

Food dilution changes the caloric density and nutrient composition of the food, relative to contol groups fed undiluted food. It is interesting that food dilution provides a positive CR-like effect in Drosophila.

[Posted by: Michael Cooper at November 18, 2004 6:07 PM]