Short-term metabolic changes during app-based dietary management in type 2 diabetes mellitus: a single-arm observational study with a separate Mendelian randomization analysis

Vollständiger Abstract

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Background We evaluated short-term metabolic changes during a structured app-based dietary management program in patients with type 2 diabetes mellitus (T2DM). In a separate analysis using independent genome-wide association study (GWAS) datasets, we examined the population-level association between genetically predicted liver fat and glycated hemoglobin (HbA1c). Methods The clinical component was a prospective single-arm observational study of 103 adults with T2DM who received an individualized 4-week dietary prescription, recorded daily intake using a mobile application, and received weekly dietitian feedback. Anthropometric and laboratory measures were compared before and after the management period using paired tests. Associations between changes in glycemic and anthropometric indicators were assessed using Spearman correlation. The separate two-sample Mendelian randomization (MR) analysis used liver fat as the exposure and HbA1c as the outcome; inverse-variance weighted (IVW) analysis was primary. Results Fasting blood glucose decreased from 7.26 ± 2.26 to 6.91 ± 2.08 mmol/L ( p = 0.011), and HbA1c decreased from 6.86 ± 1.33% to 6.65 ± 1.10% ( p < 0.001). Body weight and visceral fat area did not change significantly. The change in HbA1c was modestly correlated with the change in visceral fat area ( r = 0.284, p = 0.016). In the separate MR analysis, the primary IVW estimate did not support an association between genetically predicted liver fat and HbA1c ( β = 0.011, 95% CI − 0.019 to 0.041, p = 0.481). Nominal associations from secondary estimators were considered exploratory. Conclusion Glycemic measures were lower after the 4-week management period than at baseline, but the single-arm design prevents attribution of these changes specifically to the program. The visceral fat–HbA1c correlation was exploratory. The separate MR analysis addressed a distinct population-level question and did not provide confirmatory evidence in the primary analysis.