Dietary restriction (DR), limiting calories or specific nutrients without malnutrition, extends lifespan across diverse taxa. Traditionally, this lifespan extension has been explained as a result of diet-mediated changes in the trade-off between lifespan and reproduction, with survival favored when resources are scarce. However, a recently proposed alternative suggests that the selective benefit of the response to DR is the maintenance of reproduction. This hypothesis predicts that lifespan extension is a side effect of benign laboratory conditions, and DR individuals would be frailer and unable to deal with additional stressors, and thus lifespan extension should disappear under more stressful conditions. We tested this by rearing outbred female fruit flies (Drosophila melanogaster) on 10 different protein:carbohydrate diets. Flies were either infected with a bacterial pathogen (Pseudomonas entomophila), injured with a sterile pinprick, or unstressed. We monitored lifespan, fecundity, and measures of aging. DR extended lifespan and reduced reproduction irrespective of injury and infection. Infected flies on lower protein diets had particularly poor survival. Exposure to infection and injury did not substantially alter the relationship between diet and aging patterns. These results do not provide support for lifespan extension under DR being a side effect of benign laboratory conditions.
Bibliographical noteFunding Information:
This work was supported by the Biotechnology and Biological Sciences Research Council (BBSRC) grant number BB/M010996/1 and Leverhulme Trust grant number RPG‐2017‐181. We thank Joshua Moatt for advice and comments on the data analysis and write‐up, Jonathon Siva‐Jothy for bacterial work help, Katy M. Monteith for laboratory training and practical advice, and Megan Wallace for testing the DGRP outcross for the presence of common fly viruses.
Data Availability StatementData and associated script are available on the Dryad repository: https://doi.org/10.5061/dryad.80gb5mkq2.
- Drosophila melanogaster
- dietary restriction
- Stress, Physiological
- Biological Evolution
- Wounds and Injuries
- Diet Therapy