Johnston, S.L., Grune, T., Bell, L.M., Murray, S.J., Souter, D.M., Erwin, S.S., Yearsley, J.M., Gordon, I.J., Illius, A.W., Kyriazakis, I., and Speakman, J.R. (2006) Having it all: historical energy intakes do not generate the anticipated trade-offs in fecundity. Proceedings of the Royal Society of London Series B, Biological Sciences, 273 (1592). pp. 1369-1374.

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Abstract

An axiom of life-history theory, and fundamental to our understanding of ageing, is that animals must trade-off their allocation of resources since energy and nutrients are limited. Therefore, animals cannot 'have it all'-combine high rates of fecundity with extended lifespans. The idea of life-history trade-offs was recently challenged by the discovery that ageing may be governed by a small subset of molecular processes independent of fitness. We tested the 'trade-off' and 'having it all' theories by examining the fecundities of C57BL/6J mice placed onto four different dietary treatments that generated caloric intakes from -21 to +8.6% of controls. We predicted body fat would be deposited in relation to caloric intake. Excessive body fat is known to cause co-morbidities that shorten lifespan, while caloric restriction enhances somatic protection and increases longevity. The trade-off model predicts that increased fat would be tolerated because reproductive gain offsets shortened longevity, while animals on a restricted intake would sacrifice reproduction for lifespan extension. The responses of body fat to treatments followed our expectations, however, there was a negative relationship between reproductive performance (fecundity, litter mass) and historical intake/body fat. Our dietary restricted animals had lower protein oxidative damage and appeared able to combine life-history traits in a manner contrary to traditional expectations by having increased fecundity with the potential to have extended lifespans.

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