LC–MS–Based Untargeted Metabolomic Profiling Distinguishes Carbohydrate Restriction from Low Energy Availability in Elite Endurance Athletes

Periods of low energy availability (LEA), which are common in elite athletes, typically arise from reduced energy intake, and often involve some degree of carbohydrate (CHO) restriction. It has been previously unknown whether the metabolic profile created by energy restriction per se is distinct compared to that driven by CHO restriction. As a response, a joint study made up of researchers from Australian Catholic University, (Melbourne, Australia), Edith Cowan University (Perth, Australia) and Manchester Metropolitan University (United Kingdom) used untargeted metabolomics to examine metabolic perturbations linked to CHO restriction and energy restriction in plasma from elite male endurance athletes, with metabolomic analysis performed using liquid chromatography-mass spectrometry (LC-MS), with multivariate analysis conducted using repeated-measures analysis of variance (ANOVA) simultaneous component analysis+ (RM-ASCA+) and hierarchical clustering. A paper based on their work was published in Physiological Reports. ⁽¹⁾

Many elite athletes involved in weight-sensitive and/or endurance-based sports periodically undertake deliberate periods of reduced energy availability (EA) as part of varied training or nutritional strategies undertaken to achieve optimal performance; although energy restriction can certainly happen unintentionally, it occurs in these cases due to planned reductions in energy intake (EI) or an increase in exercise energy expenditures (EEE) so as to manipulate body composition for specific competitions. ⁽²⁾ Such routines may result in periods of LEA, often typified by a downregulation of multiple biological systems in several tissues and organs leading to insufficient energy for meeting daily bodily requirements. ⁽³⁾ While this practice has become a staple of certain athletic preparation and is often deemed a crucial element in achieving sporting success, continued exposure may result in problematic consequences, the worst of which being that the metabolic perturbations are no longer transient or reversible. ⁽⁴⁾ In addition, lengthy exposure to LEA has become associated with a variety of health-related disorders, such as reproductive dysfunction, impaired bone health, gastrointestinal dysfunction, and perturbations in glucose/lipid handling. ⁽⁴⁾

For this study, a semi-randomized controlled trial, where athletes (n = 20, all high performance male race walkers, ranging from Tier 3 [national level] to Tier 5 [world class]) completed one of three 5-day dietary interventions: high energy-high CHO (HCHO); LEA (energy-restricted, CHO-reduced); or low-CHO, high-fat (LCHF; energy-matched, CHO-restricted). Plasma samples were then taken at multiple timepoints pre- and post a standardized 25 km race walk protocol. A total of 5391 metabolic features were detected and 138 metabolites annotated. LCHF induced substantial metabolic perturbations, especially after prolonged exercise, including elevations in fatty acyls, hydroxy acids, dicarboxylic acids and acylcarnitine intermediates, responses not seen under LEA. ⁽¹⁾

“We conclude,” write the authors of the study, ⁽¹⁾ “that CHO restriction concomitant with a high-fat load induces a greater metabolic perturbation in selected lipid-based metabolites than short-term LEA exposure in elite athletes undergoing prolonged endurance exercise. These results,” they continue, “provide a foundation for subsequent investigations and underscore the importance of further characterizing lipid metabolic responses to CHO restriction and LEA using a combination of targeted metabolomic and lipidomic techniques. Understanding these metabolic responses may be crucial for athletes and sports practitioners alike, as dietary strategies involving CHO restriction may inadvertently impair recovery or long-term health when implemented during periods of sustained LEA.” ⁽¹⁾

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References

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