Dietary restriction extends lifespan across different temperatures in the fly

1. Dietary restriction (DR) has been consistently shown to extend lifespan across a range of taxa. However, it has recently been reported that DR does not extend lifespan at certain, namely lower, temperatures in flies (Drosophila melanogaster). Similar to the interpretation of other findings that appear to question DR's universality, this finding has been interpreted as suggesting that lifespan extension in response to DR is an artefact of benign laboratory conditions.

2. We re-test this hypothesis, now using a strain that shows robust lifespan extension at 25°C (across three prior experiments), and using a range of five diets across two temperatures, 18°C and 21°C.

3. We found the DR longevity response to be robust, extending lifespan irrespective of temperature. We measured fecundity as a positive control for the DR phenotype, and found, as predicted, that DR reduces egg laying.

4. We suggest differences in experimental setup, genetic lines used and variation in the diet-lifespan reaction norm are responsible for this discrepancy. In addition, starting with a strain and conditions that show a lifespan extension by DR, as we do here, and then changing environment and/or genotype promises a more robust test of DR modulating factors.

5. In conclusion, it will be important for results that question DR as a phenotype to not be overinterpreted readily, as with a substantially larger sample size and a larger range of diets we were unable to replicate this prior work.