Dyslexia is a common neurodevelopmental disorder characterized by impaired fluent or accurate word recognition and spelling, despite the individual having adequate intelligence and typical hearing and vision (1). The estimated prevalence of dyslexia ranges from 5% to 17.5% in English-speaking countries (2) and approximately 3.45% among Chinese school-aged children (3). As the most common type of learning disorder, dyslexia is associated with poor long-term academic achievements and professional development, resulting in costly burdens on individuals and society (4).

Previous studies have emphasized that children with neurodevelopmental disorders are at an increased risk of developing excess body weight. For example, Michael et al. discovered that children with attention-deficit/hyperactivity disorder (ADHD) had a 1.9-fold increased risk of being overweight and obese (5). Another study revealed a noteworthy disparity in the prevalence of overweight and obesity among autistic children aged 2–17 years compared to the general population in the United States (6). Children with intellectual disability (ID) also exhibited significantly higher odds of being obese compared to their healthy peers (7). The potential mechanisms explaining this significant association between neurodevelopmental disorders and excess body weight included unhealthy eating problems, inadequate physical activity, excessive sedentary behaviours, and antipsychotic medication taking (8–10). Individuals with autism spectrum disorder (ASD) may also exhibit conditions associated with obesity, such as sleep and gastrointestinal problems (11–13). Additionally, shared genetic liability might be another contributor to the significant association between neurodevelopmental disorders and obesity (14).

Notably, children with dyslexia are also exposed to risk factors associated with obesity, such as psychosocial stress, reduced physical activity, and maladaptive coping behaviours (15–17). However, there is a relative dearth of studies that explore the weight status among dyslexic individuals. To be best of our knowledge, only one study conducted in Iran has indicated a higher proportion of overweight and obesity among dyslexic children compared to their healthy counterparts (18). This study exclusively encompassed male students and relied on basic comparisons of proportions between the two groups. Previous studies have emphasized the importance of paying special attention to children with developmental disabilities when assessing the risk of childhood obesity (19, 20). Given the association between dyslexia and obesity-related factors, it is necessary to examine whether children with dyslexia are at an increased risk of excess body weight. Such insights could provide empirical evidence to develop targeted interventions, which may help to improve long-term health outcomes in children with dyslexia and reduce the societal and healthcare burdens associated with both conditions.

Based on the knowledge gaps above, this study utilized participants from the Tongji Reading Environment and Dyslexia (READ) program and aimed to investigate the association between dyslexia and overweight and obesity. We also explored possible sex-related differences in this potential relationship. To the best of our knowledge, this is the first study to examine the weight status of dyslexic children in China.

This study provides valuable insights into the association between neurodevelopmental disorders and unhealthy weight conditions. In this study, it was found that around 20% of dyslexic children were overweight, and over 20% exhibited obesity. Dyslexic children were more likely to be obese compared to their non-dyslexic counterparts. However, no statistically significant association was observed between dyslexia and overweight. Sex-stratified analysis found that dyslexia was significantly associated with obesity in girls, but not in boys. This study, for the first time, investigated excess body weight among dyslexic children in China. It represents the initial endeavour to investigate weight-related issues in this specific population, contributing new insights to the existing knowledge.

This study demonstrated that dyslexic children engaged in fewer physical activities, which was consistent with the previous studies (16, 29). One possible reason was that children with dyslexia were more likely to experience motor problems (30, 31) and executive dysfunction (32). The motor problems may result in dyslexic children being less willing to engage in physical activities that require special motor skills, while the impaired executive function of dyslexic children makes it challenging for them to adhere to regular and sustained exercise routines. Besides, dyslexia can heighten various challenges for children, encompassing deficits in reading and math, difficulties in handling tasks, impairments of attention, as well as issues related to memory (33–35). These challenges may result in an increased amount of time spent on learning and homework for children with dyslexia, which in turn decreases the allocation of time for exercise.

Our findings revealed an increased odds of obesity among dyslexic children, aligning with previous studies that explored the association between various neurodevelopmental disorders and obesity. Several underlying mechanisms may contribute to this observed association between dyslexia and obesity. Firstly, insufficient physical activity and sedentary behaviours are robust risk factors for obesity, and the unhealthy lifestyle of children with dyslexia may contribute to their increased risk of obesity (36). Secondly, dyslexia is also associated with an increased risk of conditions linked to obesity, such as ADHD, depression, and anxiety disorders (37–39). These comorbidities may increase the risk of obesity in children with dyslexia. Finally, polymorphisms in genes such as DRD2 and BDNF have been identified as shared factors associated with both dyslexia and obesity (40–44). These shared genetic factors may also play a role in the increased susceptibility to obesity among dyslexic children. More in-depth investigations are needed to further explore the underlying mechanisms between dyslexia and obesity.

When we further stratified the comparisons by children's sex, we observed that dyslexia was positively associated with obesity only in girls. This sex-specific association is consistent with findings from other neurodevelopmental disorders. For instance, a meta-analysis identified female sex as a potential risk factor for overweight and obesity in children with ASD (45), and another study found that ADHD was associated with obesity in adolescent girls but not in boys (46). Several mechanisms may explain this disparity. Compared to boys, girls with dyslexia may be more likely to cope with academic stress or low self-esteem through emotional eating, which may lead to excess weight gain (47). In addition, girls exhibited significantly lower levels of physical activity in this study, which may further contribute to their increased susceptibility to obesity when affected by dyslexia.

However, no significant relationship was found between dyslexia and overweight in this study. Lam and Yang also found that ADHD was linked to obesity but not overweight in Chinese adolescents (48). A meta-analysis comprising 15 studies revealed that individuals with ASD exhibited a higher prevalence of obesity compared to controls, while the prevalence of overweight did not differ significantly from that in the control group (49). In contrast, another study suggested a consistently elevated risk of overweight and obesity in individuals with ADHD (50). The reason for these inconsistent results remains unclear. The relationship between neurodevelopmental and excessive body weight is intricate, even bidirectional. Higher-quality studies are imperative to explore the correlations and causal relationships.

Some limitations were presented in this study. Firstly, because of the cross-sectional nature of the collected data, the causal relationship between dyslexia and obesity remains unclear. Secondly, children's height and weight were assessed based on parent-reported rather than objective measurements, which might result in some inaccuracies in measurements. However, evidence-based research has shown that parent-reported height and weight can provide a highly accurate classification of children's weight status, thereby supporting the reliability of our findings (51). Thirdly, the study population was restricted to specific regions and schools, which may limit the generalizability of the findings to broader populations. Finally, future considerations should encompass additional potential factors associated with obesity for children with dyslexia, such as eating patterns and sleep problems. Despite these limitations, this study provided new clues and considerations for future investigations, especially within the limited research context regarding the correlation between dyslexia and obesity.

In conclusion, this study provided evidence that children with dyslexia were at an increased risk of obesity, with this association was more significant among girls. Based on our findings, it is reasonable to implement weight screening and develop strategies for weight control among dyslexic children. Further high-quality studies are required to validate this association and delve into the underlying mechanisms of obesity in this special population.