User perceptions of continuous glucose monitoring during high and low carbohydrate diets in trained, non-diabetic athletes

Objective To examine the user experience and perceived effectiveness of continuous glucose monitoring (CGM) devices in highly trained, non-diabetic male athletes during low-carbohydrate high-fat (LCHF) and high-carbohydrate low-fat (HCLF) dietary interventions. Equipment and methods Randomized, counterbalanced, crossover dietary intervention with mixed-methods analysis. Ten non-diabetics, middle-aged (aged 30–50 years) highly trained male athletes completed two isocaloric 31-day diet phases (low-carbohydrate high-fat and high-carbohydrate low-fat), separated by a two-week washout. Diets were self-administered under free-living conditions, and glucose was monitored using Freestyle Libre 2 continuous glucose monitors. Well-being was assessed using the World Health Organization Five Well-Being Index (0–100 scale), and health-related quality of life was evaluated via the EuroQol-5D Visual Analogue Scale (0–100 scale). Satisfaction and user experience with CGM were measured using a modified CGM-SAT survey and open-ended responses. Quantitative data were analyzed using paired t -tests and repeated measures ANOVA. Thematic analysis of qualitative responses followed Braun and Clarke's framework, and a heatmap was used to visualize theme co-occurrence. Results WHO-5 scores increased slightly in the LCHF group (pre: 79.2% ± 11.4, post: 81.2% ± 14.1) and decreased in the HCLF group (pre: 81.2% ± 7.1, post: 78.4% ± 10.9), with no statistically significant changes ( P > 0.05). EQ-5D scores improved in the LCHF group (85.5 ± 9.5 to 89.1 ± 5.9) and declined in the HCLF group (89.2 ± 8.2 to 86.8 ± 9.6), also without significant condition or interaction effects. Thematic analysis revealed three major themes: Empowerment & Learning , Usability & Practicality , and Enhancement & Interest . Participants valued CGM for real-time feedback and dietary awareness but noted challenges such as sensor adhesion and scanning frequency. Heatmap analysis showed strong co-occurrence between usability and engagement, indicating that ease of use enhanced behavioral adaptation. CGM may be a useful tool for promoting dietary awareness and self-management among non-diabetic athletes. Despite no statistically significant improvements in well-being or health state, participants reported meaningful personal insights. Practical challenges with device usability warrant attention. These findings support further exploration of CGM in personalized nutrition and behavioral interventions targeting performance and adherence.