The “Fat but Fit” paradox in the academic context: relationship between physical fitness and weight status with adolescents’ academic achievement

The present study aimed to analyze the relationship between obesity and different physical fitness markers with academic achievement in adolescents, as well as to check if the “Fat but Fit paradox” is applicable in this context. A total of 188 participants (83 boys) ranging from 12 to 18 years (14.51 ± 1.29 years) underwent a series of fitness tests, and were categorized as “fit” or “unfit” attending to their estimated cardiorespiratory fitness (above or below 42 and 35 ml·kg−1·min−1 for boys and girls, respectively). Participants were also categorized according to their body mass index as having overweight/obesity or not. A variety of fitness markers (i.e., cardiorespiratory fitness, lower-body power, sprint time, and flexibility) were positively associated with academic achievement (all p < 0.05), but no associations were found for upper-body power, upper-limb coordination or agility. Both being fit (β = 0.652, 95% confidence interval: 0.001–1.302) and normoweight (β = 1.085, 0.171–1.999) were positively associated with academic achievement. A higher academic achievement (p = 0.021) was found for fit and normoweight individuals compared to unfit and overweight/obese ones, but no differences were found for the remaining subgroups. These findings suggest that an optimal physical fitness might attenuate the negative consequences induced by obesity on academic achievement.