Fitness differences according to BMI categories: a new point of view

Many studies have reported negative association between fitness level and BMI categories but the lack of body weight correction and the systematic use of physical endurance test made these differences controversial. Thus, the aim of this study was the assessment of physical fitness level associated to BMI using alternative tests.

BMI was calculated as body mass/stature2 while fitness level was assessed using field test. In particular, Sit and Reach (SAR), Standing Broad Jump (SBJ), Shuttle Run Test 5 mx 10 (SHR), Sit ups (SUP), Bent arm hang (BAH) were assessed in 2545 students. Subsequently, normal weight/overweight/obesity/underweight/thinness students were classified according to the cut-off points defined in literature and then the relative fitness results.

The performances in SBJ showed very low differences between BMI categories such as for SUP test. The effects size in SHR were low or close to moderate while in BAH thin students revealed high performance than normal/overweight peers. In SAR test no clear trends in the BMI categories were observed.

All test (exluding BAH) were similar for normal, overweight and thin students. This finding can be useful to teachers to encourage over/under-weighted students to adopt active life style because they are close to normal weight counterparts.