1: People with Greater "Fluctuations" in Winter Weight Gain and Summer Weight Loss Are More Prone to Declining Kidney Function — Analysis of 6,700 People in the Japan Diabetes Clinical Data Management Study (JDDM) —

Diabetes Care.    

2026 Jun;49(6):990-998. doi: 10.2337/dc26-0082

Toki R, Sakamoto M, Yuki M, Iida M, Yamazaki M, Ichikawa S, Horiuchi R, Maegawa H, Okamura T, Takebayashi T.

In patients with diabetes, fluctuations in blood glucose levels and Blood Pressure are known to be independent risk factors for diabetic complications. Regarding body weight, weight cycling—repeated significant increases and decreases—has been reported to be associated with cardiovascular disease and mortality, but its impact on kidney function has remained unclear. In particular, seasonal fluctuations where weight increases in winter and decreases in summer are a common phenomenon and have generally been considered harmless. In this study, using the JDDM registry in which diabetes specialist medical institutions nationwide participate, we calculated the magnitude of seasonal fluctuations for 6,700 individuals with type 2 diabetes from their monthly body weight (BMI) using a method called STL decomposition. A clear seasonal rhythm was observed in the overall population, peaking around February and reaching its minimum around July. Furthermore, as a result of the association analysis with kidney function, the group with the largest fluctuations had approximately 1.7 times the risk of a 40% or greater decline in eGFR compared to the group with the smallest fluctuations. We also confirmed that even after adjusting for age, sex, and degree of obesity, the group with larger fluctuations had a faster rate of eGFR decline over time. The results of this study suggest that a new indicator that can be easily identified without special testing, such as seasonal weight fluctuation, may be useful in future clinical practice for diabetes.

(Department of Preventive Medicine and Public Health: Toru Takebayashi, Ryodai Toki)