Abstract
Relative Energy Deficiency in sport (REDs) results from problematic Low Energy Availability (LEA) whereby insufficient energy is consumed to support the energy demands of exercise as well as daily physiological functions, leading to impaired health and performance. There are 14 proposed physiological systems that can be affected by REDs, one of which is lipid metabolism. However, minimal research has been undertaken and none in a clinically-diagnosed REDs population. Due to the key roles lipids play in the body including energy storage, cell structure, hormone synthesis, and cell signalling, possible impairments can have detrimental effects on the individual. Therefore, this pilot study aimed to investigate plasma lipids (total cholesterol, triglycerides (TRIGL), high-density lipoprotein (HDL), and low-density lipoprotein (LDL)) in a clinically diagnosed female REDs population. It is hypothesised that active females with REDs will show unfavourable plasma lipid profiles, specifically, raised total cholesterol and LDL, and reduced HDL compared to matched controls.
Five participants clinically diagnosed with REDs by a sports physician and five participants without REDs (CONTROLS) were recruited. Plasma lipids were determined at the time of diagnosis for REDs participants as part of routine testing; Control participants provided fasting blood samples during the follicular stage of their menstrual cycle. Control samples were then analysed for oestrogen, progesterone and plasma lipids, total cholesterol, TRIGL and HDL. LDL was calculated using the Friedewald formula. Results are presented as mean ± standard deviation, and number (%).
Control participants displayed a higher mean total cholesterol (4.71 ± 0.49 mmol/L) compared to REDs (4.44 ± 0.83 mmol/L) with 4/5 (80%) control and 3/5 (60%) REDs participants having total cholesterol values above Tr Whatu Ora Health NZ reference values. All participants (n=10/10, 100%) plasma TRIGL and HDL were within ranges, (TRIGL: 1.21 ± 0.24 mmol/L vs 0.70 ± 0.11 mmol/L CONTROL vs REDs and HDL: CONTROL 1.72 ± 0.58 mmol/L vs REDs 1.64 ± 0.4 mmol/L). REDs participants had higher mean plasma LDL compared to the controls (2.50 ± 0.93mmo/L vs 2.28 ± 0.277mmol/L) with 2/5 (40%) of the REDs participants compared to 1/5 (20%) control above reference values. Oestrogen and progesterone concentrations for the controls were all within reference ranges for the follicular phase.
The small sample size limits interpretation of the findings but suggests some differences may exist. This study reflects difficulties in recruiting a diagnosed REDs population which may explain why inferences have been made based on proxy measures in the published literature. These findings do suggest further investigations in clinically diagnosed populations and plasma lipids are required, given the important role of plasma lipids for many aspects of health and performance.