Purpose: The purpose of this study was to determine the relationship between 20m shuttle run (20mSRT) performance and a substantial increase in waist circumference (WC) with aging in Japanese middle-aged adults.Methods: One hundred and fifty-six Japanese middle-aged adults (40-64 yrs; 40 males, 116 females) participated in this study. Baseline data on 20mSRT, height, weight, WC, alcohol habit, smoking habit and the use of medication were collected from 2003 to 2004. Follow-up data on height, weight and WC were collected in 2008. The 20mSRT results were divided into gender-specific quartiles. A logistic regression analysis was used to predict a substantial increase in the WC (5 cm or more) during the follow-up.Results: During the follow-up, 44 people had a substantial increase in the WC. Independently from sex, age, height (baseline), weight (baseline), WC (baseline), alcohol habit, smoking habit and the use of medication, the highest quartile of 20mSRT was significantly associated with significantly lower odds ratio of a substantial increase in WC (OR: 0.07, 95%CI: 0.01-0.36) in comparison to the lowest quartile of 20mSRT. Furthermore, after additional adjustment for change in weight during follow-up, the highest quartile remained significantly predictive of a substantial increase in the WC, with odds ratio of 0.07 (95%CI: 0.01-0.39).Conclusions: These results indicate that the 20mSRT performance is a significant predictor of a substantial increase in the WC with aging in Japanese middle-aged adults.