Impact of Weight Change on Type 2 Diabetes Risk: A Prospective Study in a Japanese Population.

Context: Although weight reduction has been shown to reduce type 2 diabetes risk, the threshold of weight change, including increase and decrease, associated with the risk remained unclear.

Objective: We investigated the association between weight change and the risk of type 2 diabetes.

Methods: The participants were 41,539 nondiabetic residents (16,914 men, 24,625 women) in Kochi, Japan, who underwent health examinations between April 2013 and March 2015. The association between 1-year weight change and the risk of type 2 diabetes was assessed using Cox proportional hazards models.

Results: During a mean 5.7-year follow-up, 3,564 new-onset type 2 diabetes cases were documented.　Compared with participants with stable body weight (<1.0 % change), those with weight decreases of 1.0%-2.9%, 3.0%-4.9% and ≥5.0% showed a lower risk of type 2 diabetes [16% (8%-24%, p<0.001), 25% (15%-34%, p<0.001), and 26% (14%-36%, p<0.001), respectively]. Conversely, those with weight increases of 1.0%-2.9%, 3.0%-4.9% and ≥5.0% showed a higher risk [15% (4%-26%, p=0.005), 35% (20%-53%, p<0.001), and 51% (29%-76%, p<0.001), respectively]. These associations persisted among individuals with BMI ≥25 kg/m2 or ≥10 kg weight gain since age 20. Among individuals with BMI 22-25 kg/m2, weight increase of ≥3.0% showed a higher risk. No associations were observed in individuals with BMI <22 kg/m2 or aged ≥75.

Conclusion: Both preventing weight gain and reducing weight are important for lowering the risk of type 2 diabetes in Japanese individuals, particularly among those with BMI ≥22kg/m2.