Although there is a growing consensus about the positive relationship between prevention of overweight/obesity and academic performance in children, relevant studies targeting the relationship between underweight and academic performance are scarce. This study aimed to examine the longitudinal relationship of favorable weight change to academic performance in schoolchildren. We analyzed 2-year longitudinal data derived from 197 seventh-grade children aged 12-13 years. Academic performance was assessed using the total grade points of five academic subjects. Body mass index (BMI) was calculated as body weight (kg)/height (m2). A significant interaction effect of baseline BMI and BMI changes over 2 years (B = -0.10, SE B = 0.03, β = -0.40, t = -3.37, p < 0.001) was noted after controlling for confounders such as socioeconomic status, afterschool learning duration, screen time, exercise habits, and cardiorespiratory fitness. When the centered baseline BMI was outside the interval [-2.49, 3.21], the slope of the change in BMI was significant (p < 0.05). Simple slope analyses revealed a positive relationship of weight gain when baseline BMI = mean - 1 SD (B = 0.40, SE B = 0.18, β = 0.31, t = 2.20, p = 0.03) and weight loss when baseline BMI = mean + 1 SD (B = -0.26, SE B = 0.13, β = -0.20, t = -1.97, p = 0.05) to total grade points of five school subjects. A split-group validation was performed and robust results of original analyses were detected (i.e., significant interaction effect of baseline BMI and BMI changes over 2 years (group A: B = -0.11, SE B = 0.05, β = -0.47, t = -2.39, p = 0.02; group B: B = -0.14, SE B = 0.05, β = -0.47, t = -2.78, p = 0.007). Favorable changes in weight status, i.e., weight loss in children with overweight/obesity and weight gain in children with mild underweight/underweight, have a positive influence on academic performance in children independent of socioeconomic factors, learning habits, screen time, exercise habits, and cardiorespiratory fitness.

中文翻译：

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体重变化与儿童学习成绩的纵向关系。

尽管关于预防超重/肥胖与儿童学业成绩之间呈正相关关系的共识日益增长，但针对体重过轻与学业成绩之间关系的相关研究却很少。这项研究旨在探讨有利的体重变化与学龄儿童学业成绩之间的纵向关系。我们分析了197位12-13岁的7年级儿童的2年纵向数据。使用五门学科的总成绩评估学业成绩。体重指数（BMI）以体重（kg）/身高（m2）计算。在控制了诸如社会经济地位等混杂因素后，注意到基线BMI和BMI在2年内的变化具有显着的交互作用（B = -0.10，SE B = 0.03，β= -0.40，t = -3.37，p <0.001），课后学习时间，屏幕时间，运动习惯和心肺健康。当居中基线BMI在区间[-2.49，3.21]之外时，BMI变化的斜率很明显（p <0.05）。简单的斜率分析显示，当基线BMI =平均值-1 SD（B = 0.40，SE B = 0.18，β= 0.31，t = 2.20，p = 0.03）时体重增加与基线BMI =平均值+ 1时体重减轻呈正相关SD（B = -0.26，SE B = 0.13，β= -0.20，t = -1.97，p = 0.05）至五个学校科目的总成绩。进行分组验证并检测到了原始分析的可靠结果（即，基线BMI和BMI变化在2年内具有显着的交互作用（A组：B = -0.11，SE B = 0.05，β= -0.47，t = -2.39，p = 0.02； B组：B = -0.14，SE B = 0.05，β= -0.47，t = -2.78，p = 0.007）。