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Life expectancy is about 5 years shorter for men than for women.1 At any given age, men are more vulnerable than women to death from most major causes, including infections, cancer and cardiovascular disease.1 Lifestyle and stress undoubtedly play the same role in this disparity as in other health disparities, particularly given historically higher smoking rates for men than for women. Whether these factors provide a comprehensive explanation and actionable targets of intervention is less clear, particularly as these factors do not fully explain men's cardiovascular disadvantage.2 Here, to provide another perspective, the sexual disparity in life expectancy is considered in the context of an existing well-established theory from evolutionary biology. Life history theory suggests that animals, including humans, employ environmentally driven strategies to maximise Darwinian fitness, that is, reproductive success.3 Optimal strategies for reproductive success likely differ by sex, because men may have far more children than women4 but reproductive costs are far higher for women. As such, not only does a strategy aimed at fitness differ from the public health goal of long and healthy life but may also have sex-specific implications, and so be relevant to the shorter lifespan in men than in women.
Specifically, life history strategies may involve trading off growth or reproduction against longevity,3 with the role of less growth well known but suppressing the reproductive axis may also increase lifespan;5 and promoting the reproductive axis may reduce lifespan. For example, a high-protein diet in mice results in bigger gonads and shorter life, while a high-carbohydrate diet results in smaller gonads and longer life;6 interestingly mice prefer a higher protein diet.6 In humans, the reproductive axis in women is suppressed at menopause, and artificial supplementation with reproductive hormones in postmenopausal women is not beneficial for lifespan. …