Sustained restriction of food intake can extend life in a diverse array of organisms. This phenomenon has been demonstrated in species of rotifers, nematodes, arthropods, and studied in detail in rodents. Here, we propose a hypothesis as a framework for interpreting this phenomenon. Our hypothesis connects food intake, reproduction, health, and longevity. We draw attention to a feature of dietary restriction- a concomitant decline in reproductive capacity. This has been shown in several species. In rodents, continued dietary restriction, as well as reduced food availability in the wild, results in delayed onset of puberty and reduced fertility. We submit that in unrestricted animal, food intake is geared towards attaining, maintaining, and improving reproductive capacity. This level of food intake produces a neuroendocrine and metabolic internal milieu markedly different from the one seen in the dietary-restricted state (e.g.: in hypothalamic-pituitary-gonadal and adrenal axes).This neuroendocrine and metabolic milieu prepares the body for reproduction. At the same time, some of the components of this milieu are detrimental to health in the long term. This makes sense in terms of evolution- in the course of evolution, what is selected for is reproductive success and not health in old age. In dietary restriction experiments, the animal is prevented from eating enough to attain, maintain, - or improve- reproductive capacity. The neuroendocrine and metabolic internal milieu associated with the high level of food intake does not materialize, detrimental effects resulting from that milieu do not materialize, and- at least in the artificially created environment of the laboratory- the animal lives longer.