Development of food intake controls: neuroendocrine and environmental regulation of food intake during early life.

This article is part of a Special Issue "Energy Balance". The development of neuroendocrine regulation of food intake during early life has been shaped by natural selection to allow for optimal growth and development rates needed for survival. In vertebrates, neonates or early larval forms typically exhibit "feeding drive," characterized by a developmental delay in 1) responsiveness of the hypothalamus to satiety signals (e.g., leptin, melanocortins) and 2) sensitivity to environmental cues that suppress food intake. Homeostatic regulation of food intake develops once offspring transition to later life history stages when growth is slower, neuroendocrine systems are more mature, and appetite becomes more sensitive to environmental or social cues. Across vertebrate groups, there is a tremendous amount of developmental plasticity in both food intake regulation and stress responsiveness depending on the environmental conditions experienced during early life history stages or by pregnant/brooding mothers. This plasticity is mediated through the organizing effects of hormones acting on the food intake centers of the hypothalamus during development, which alter epigenetic expression of genes associated with ingestive behaviors. Research is still needed to reveal the mechanisms through which environmental conditions during development generate and maintain these epigenetic modifications within the lifespan or across generations. Furthermore, more research is needed to determine whether observed patterns of plasticity are adaptive or pathological. It is clear, however, that developmental programming of food intake has important effects on fitness, and therefore, has ecological and evolutionary implications.