Low energy availability: history, definition and evidence of its endocrine, metabolic and physiological effects in prospective studies in females and males

Energy availability (EA) is deined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insuicient EA due to increased exercise, reduced energy intake, or a combination of both, is a potent disruptor of the endocrine milieu. As such, EA is conceived as a key etiological factor underlying a plethora of physiological dysregulations described in the female athlete triad, its male counterpart and the Relative Energy Deiciency in Sport models. Originally developed upon female-speciic physiological responses, this concept has recently been extended to males, where experimental evidence is limited. The majority of data for all these models are from crosssectional or observational studies where hypothesized chronic low energy availability (LEA) is linked to physiological maladaptation. However, the body of evidence determining causal efects of LEA on endocrine, and physiological function through prospective studies manipulating EA is comparatively small, with interventions typically lasting ≤ 5 days. Extending laboratory-based indings to the ield requires recognition of the strengths and limitations of current knowledge. To aid this, this review will: (1) provide a brief historical overview of the origin of the concept in mammalian ecology through its evolution of algebraic calculations used in humans today, (2) Outline key diferences from the ‘energy balance’ concept, (3) summarise and critically evaluate the efects of LEA on tissues/systems for which we now have evidence, namely: hormonal milieu, reproductive system endocrinology, bone metabolism and skeletal muscle; and inally (4) provide perspectives and suggestions for research upon identiied knowledge gaps.     «

Energy availability (EA) is deined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insuicient EA due to increased exercise, reduced energy intake, or a combination of both, is a potent disruptor of the endocrine milieu. As such, EA is conceived as a key etiological factor underlying a plethora of physiological dysregulations described in the female athlete triad, its male counterpart and the Relative Energy Deiciency i...     »