In the present study, the effect of artificial alterations in excess body weight on exercise performance and metabolic responses was investigated. Ten subjects(5 males, 5 females) who were university students with written informed consent, were recruited. For artificial overloading(0%, 10%, 15%, 20%) in body weight of each subject, the self-made vests with iron ball (6g/each) were used. Muscular endurance, power, agility, balance, reaction time, and running time were measured in order to evaluate exercise performance while heart rate(HR), maximal oxygen uptake(VO_2max), and the level of lactic acid were measured to determine metabolic responses in each subject. The results showed that HR, muscular endurance, power, and reaction time in 20% excess body weight and running time in 10% excess body weight were significantly decreased, whereas agility, balance, VO_2max, and the level of lactic acid were not affected by 20% excess body weight. In related to sex, HR and muscular endurance were altered in male, while power, reaction time, and running time were changed both in male and female. Based on these results, it can be suggested that 20% excess body weight have a negative effect on exercise performance and partly metabolic response, especially in male, thus reduction of body weight without loss of lean body mass improve exercise performance and metabolic responses in part.