Enhancement of posture sway with backpack weight carrying by eye closure and reduced support polygon surface

•Backpack weight carrying reproduces the posture sway in obese patients.•Reduced visual acuity often occurs in obese patients due to type 2 diabetes.•Eye closure and reduced polygon support are added to weight carrying.•Both conditions augment the posture sway elicited by weight carrying.•In obese patients, reduced vision and support polygon enhance the risk of fall.