Reasons for and Consequences of Low Energy Availability in Female and Male Athletes: Social Environment, Adaptations, and Prevention

Abstract

Low energy availability (LEA) represents a state in which the body does not have enough energy left to support all physiological functions needed to maintain optimal health. When compared to the normal population, athletes are particularly at risk to experience LEA and the reasons for this are manifold. LEA may result from altered dietary behaviours that are caused by body dissatisfaction, the belief that a lower body weight will result in greater performance, or social pressure to look a certain way. Pressure can also be experienced from the coach, teammates, and in this day and age through social media platforms. While LEA has been extensively described in females and female athletes have started fighting against the pressure to be thin using their social media platforms, evidence shows that male athletes are at risk as well. Besides those obvious reasons for LEA, athletes engaging in sports with high energy expenditure (e.g. rowing or cycling) can unintentionally experience LEA; particularly, when the athletes' caloric intake is not matched with exercise intensity. Whether unintentional or not, LEA may have detrimental consequences on health and performance, because both short-term and long-term LEA induces a variety of maladaptations such as endocrine alterations, suppression of the reproductive axis, mental disorders, thyroid suppression, and altered metabolic responses. Therefore, the aim of this review is to increase the understanding of LEA, including the role of an athlete's social environment and the performance effects related to LEA.

Fig. 1

Components of total daily energy expenditure and adaptions to low energy availability are shown. a Total daily energy expenditure (TDEE) consists of the resting energy expenditure (REE) and the non-resting energy expenditure (NREE). NREE can be further subdivided into the thermic effect of food (TEF), non-exercise activity thermogenesis (NEAT), and exercise activity thermogenesis (EAT). Of those components, NEAT and EAT describe energy expended through physical activity (PA). b When energy availability is low, either by restricted dietary energy intake or increased energy exercise expenditure (EEE), metabolic adaptions to conserve energy occur. Those encompass a decline in basal metabolic rate (BMR), NEAT, and, if caloric intake is restricted, also in TEF. Generally, EAT will decrease as well but may be elevated in individuals increasing their training volume. Therefore, adaptations in this component are variable. Figure modified according to MacLean et al. [70]

Fig. 2

Overview of selected body-wide effects due to low energy availability (LEA). On the left, body-wide effects of LEA: lower insulin, leptin, insulin-like growth factor 1 (IGF-1), and triiodothyronine (T3) as well as lower oestradiol and progesterone in female and lower testosterone and oestradiol in male athletes. Their influence on lower energy expenditure and/or decreased bone mass density (BMD) is depicted by the arrows. In the middle, alterations in substrate: lower glucose, higher free fatty acids (FFA), higher glycerol, higher cholesterol, and β-hydroxybutyrate. These alterations, combined with lower glycogen stores and an increased percentage of fat-free mass (FFM), potentially increase lipolysis and decrease glycolysis

Fig. 3

Interrelation between an athlete’s body weight, LEA and performance. a Depending on the influence of body weight (BW) on performance, weight loss may mask underperformance in athletes experiencing low energy availability (LEA). Despite the negative consequences of LEA on performance, athletes may stay at the same level, when the positive influence of lower body weight is equal to the negative effect of LEA on performance. b When the positive influence of BW on performance outweighs the negative influence of LEA on performance, athletes may even get better, although they cannot exploit their full potential. c However, when negative adaptations due to LEA are greater than the positive influence of weight loss, performance deficits may be clearly associated with LEA