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 - Dongping Xu; Yumei Qi; Ping Zheng; Huijuan Xiao; Linlin Shi; Xiaoxiao Tian; Yue Li; Xiaoli Zhou (Frontiers in Public Health, 2026)