身體質量指數（Body Mass Index，BMI）過高與過低時，均會造成身體相關疾病。本研究企圖從不同的BMI指數切點分為「過輕」、「適中」、「過重」、「輕度肥胖」、「中度肥胖」、及「重度肥胖」六個群組，並比較各組體適能表現上的差異。受試者為中部某科技大學91至100學年度間大學新生各項體適能平均資料，共計9359人。研究結果發現：（一）男生有26.71%，女生則有15.2%的人BMI有過重或肥胖的現象。（二）BMI「過輕」時，影響大學男女生的柔軟度表現，且在各分組中表現最差。（三）女生不同的BMI分組，在腹部肌力與肌耐力方面，無統計上的顯著差異；男生「中度肥胖」及「重度肥胖」者在腹部肌力與肌耐力的表現上最差。（四）女生BMI「過輕」者在瞬發力的表現上顯著優於「中度肥胖」者；男生BMI「過輕」、「適中」者在瞬發力的表現上顯著優於「過重」及肥胖者。不論男女，BMI指數越高時瞬發力的表現似乎越差。（五）男女生同樣發現BMI「較輕」或「適中」者，在心肺耐力的表現上優於BMI「中度肥胖」、及「重度肥胖」者。現階段學生BMI的增加主要來自於體重的增加，各校在推動體適能的目標上，除飲食的控管建議外，可將降低體重與改善心肺適能列為首要目標，體重的降低除改善BMI外，也可促進各項體適能的表現。

The purpose of this study was to compare of physical fitness among different BMI (Body Mass Index, BMI) levels in university. The participants included 9,359 freshmen of National Formosa University from 1996 to 2011. There are assigned on six separate groups of ”underweight”(BMI＜18.5), ”normal”(18.5≦BMI＜24), ”overweight”(24≦BMI＜27), ”obese, class 1”(27≦BMI＜30), ”obese, class 2”(30≦BMI＜35), ”morbidly obese”(BMI≦35). Anthropometric measures included body composition (BMI), sit-and-reach of flexibility test, sit-ups (in 30sec and one minute) of muscular strength and endurance test, standing long jump of power test, and 800M(female)/1600M(male) run-walk of cardiovascular fitness test. The results included five points: first, there are 26.71% male and 15.2% female BMI have overweight or obese. Second, male and female students have poor flexibility performance when BMI is underweight. Third, there is no significant difference of sit-ups in different female BMI groups. Male has poor performance of sit-ups when BMI was ”obese, class 2” and ”morbidly obese”. Fourth, there is significant difference of power performance when BMI is ”underweight” than ”obese, class 2” in female. There is significance difference of power performance when BMI are ”underweight” and ”normal” than ”overweight” and obesity in male. Finally, there is significant difference of cardiovascular fitness when BMI is ”underweight” or ”normal” than ”obese, class 2” and ”morbidly obese” in freshmen. High BMI had the greatest impairments in physical fitness. Therefore, the study recommended that the first goal should be to reduce the weight of freshmen and improve students' cardiovascular fitness in university.