Continuous Glucose Monitoring in the Assessment of Low Energy Availability and Relative Energy Deficiency in Sport (REDs) in Athletes Without Diabetes: A Critical Narrative Review

Background: Continuous glucose monitoring (CGM) has been proposed to support assessment of low energy availability (LEA) and Relative Energy Deficiency in Sport (REDs), but its diagnostic value is uncertain. Aim: To critically evaluate CGM evidence relevant to LEA and REDs in athletes without diabetes. Material and methods: Two PubMed searches on 1 October 2026 yielded 145 unique records. AI-assisted assessment informed a purposive narrative synthesis of experimental, clinical, observational and measurement-agreement studies, supplemented by previously identified sources. Results: Severe short-term energy restriction reduced sensor glucose in one experiment, whereas studies of controlled LEA, nutritional intervention and clinically diagnosed REDs did not consistently identify differences in aggregate glucose metrics. Dietary composition, training, recovery and measurement conditions complicated interpretation. No reviewed study established a validated CGM threshold for identifying or excluding REDs. Conclusions: CGM remains an investigational adjunct. Low readings do not confirm LEA or REDs, and an unremarkable profile does not exclude them. Prospective validation must establish whether CGM adds information beyond nutritional and clinical assessment.