Exercise Training in the Normal Female: Effects of Low Energy Availability on Reproductive Function

Loucks, Anne B.

doi:10.1007/978-3-030-33376-8_11

Cited by 7 publications

(5 citation statements)

References 101 publications

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“…This original definition evolved through time (Loucks 2020 ) with three sequential algebraic formulas which were refined with the aim of better representing the dietary energy available for key tissues and systems (Table 1 ). In the first definition, EA is expressed as energy intake minus gross exercise energy expenditure reported relative to total body mass (Loucks and Callister 1993 ).…”

Section: The Birth and History Of Energy Availability As A Concept Anmentioning

confidence: 99%

“…In the third and most current definition, it is recognised that the value of gross exercise energy expenditure used in the previous definitions includes contribution of resting metabolic rate and non-exercise activity that should be subtracted to provide a net value of exercise energy expenditure (Loucks et al 1998 ). Further details of these definitions can be found elsewhere (Loucks 2014 , 2020 ).…”

Section: The Birth and History Of Energy Availability As A Concept Anmentioning

confidence: 99%

“…The most current description of energy availability (EA) defines it as the difference between energy intake (EI) and exercise energy expenditure (EEE), expressed relative to an individual’s lean body mass (LBM, Table 1 ), representing the daily amount of energy ‘available’ to sustain all physiological functions outside of exercise (Loucks 2020 ). Research addressing the effect of different levels of EA on hormonal status of the hypothalamic-pituitary-thyroid axis (Loucks and Heath 1994a ), hypothalamic-pituitary-ovarian axis (Loucks and Thuma 2003 ) and markers of bone resorption and formation (Ihle and Loucks 2004 ) in young lean sedentary women established a ‘threshold’ of ~ 30 kcal/kg LBM/day below which a disruption of the normal hormonal milieu occurs.…”

Section: Introductionmentioning

confidence: 99%

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

2020

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Energy availability (EA) is defined as the amount of dietary energy available to sustain physiological function after subtracting the energetic cost of exercise. Insufficient 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 Deficiency in Sport models. Originally developed upon female-specific 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 cross-sectional or observational studies where hypothesized chronic low energy availability (LEA) is linked to physiological maladaptation. However, the body of evidence determining causal effects of LEA on endocrine, and physiological function through prospective studies manipulating EA is comparatively small, with interventions typically lasting ≤ 5 days. Extending laboratory-based findings to the field 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 differences from the ‘energy balance’ concept, (3) summarise and critically evaluate the effects of LEA on tissues/systems for which we now have evidence, namely: hormonal milieu, reproductive system endocrinology, bone metabolism and skeletal muscle; and finally (4) provide perspectives and suggestions for research upon identified knowledge gaps.

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Section: The Birth and History Of Energy Availability As A Concept Anmentioning

confidence: 99%

Section: The Birth and History Of Energy Availability As A Concept Anmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2020

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“…The hypothalamic‐pituitary‐ovarian axis . The negative effects of LEA on female reproductive endocrinology and physiology have been thoroughly researched (Loucks, 2020). Available evidence suggests that LEA is the main cause of functional hypothalamic amenorrhea and disrupts normal endocrine responses during the early follicular phase, such as reducing pulse frequency and increased pulse amplitude of luteinizing hormone (LH) (Loucks, 2006; Loucks & Thuma, 2003; Loucks & Verdun, 1998; Loucks et al, 1998).…”

Section: Measurement and Interpretation Of Blood Markers As An Altern...mentioning

confidence: 99%

Low energy availability in female athletes: From the lab to the field

Heikura

Stellingwerff

Areta

2021

European Journal of Sport Science

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Decades of laboratory research have shown impairments to several body systems after only 4-5 days of strictly controlled consistent low energy availability (LEA); where energy availability (EA) = Energy Intake (EI) -Exercise Energy Expenditure (EEE) / Fat-Free Mass. Meanwhile, cross-sectional reports exist on the interrelatedness of LEA, menstrual dysfunction and impaired bone health in females (the Female Athlete Triad). These findings have demonstrated that LEA is the key underpinning factor behind a broader set of health and performance outcomes, recently termed as Relative Energy Deficiency in Sport (RED-S). There is utmost importance of early screening and diagnosis of RED-S to avoid the development of severe negative health and performance outcomes. However, a significant gap exists between short-term laboratory studies and cross-sectional reports, or clinically field-based situations, of long-term/chronic LEA and no definitive, validated diagnostic tests for RED-S exist. This review aims to highlight methodological challenges related to the assessment of the components of EA equation in the field (e.g. challenges with EI and EEE measures). Due to the uncertainty of these parameters, we propose the use of more chronic "objective" markers of LEA (i.e. blood markers). However, we note that direct extrapolations of laboratory-based outcomes into the field are likely to be problematic due to potentially poor ecological validity and the extreme variability in most athlete's daily EI and EEE. Therefore, we provide a critical appraisal of the scientific literature, highlighting research gaps, and a potential set of leading objective RED-S markers while working in the field.

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“…Moreover, some individuals may also exhibit pre-existing disordered eating (DE) behaviours or a clinically diagnosed eating disorder (ED), which might perpetuate a cycle of underfuelling and/or overtraining (Loucks, 2020). It is important to note, however, that RED-S can occur both in the presence and absence of such psychopathology (Mountjoy et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“It's hard to find balance when you're broken”: Exploring female endurance athletes’ psychological experience of recovery from relative energy deficiency in sport (RED-S)

Langbein

Martín

Allen‐Collinson

et al. 2022

Performance Enhancement & Health

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Exercise Training in the Normal Female: Effects of Low Energy Availability on Reproductive Function

Cited by 7 publications

References 101 publications

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

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

Low energy availability in female athletes: From the lab to the field

“It's hard to find balance when you're broken”: Exploring female endurance athletes’ psychological experience of recovery from relative energy deficiency in sport (RED-S)

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