Attentional Capacity, Weight Status and Diet Quality in Schoolchildren

Pedro José Carrillo-López

Abstract

The scientific literature suggests that following a healthy diet and maintaining an optimal weight status is associated with multiple benefits across dimensions of health. This study examines the relationship between weight status and diet quality with attentional capacity in primary school children. For this purpose, an empirical, quantitative, cross-sectional study was carried out on a sample of 209 Spanish schoolchildren with a mean age of 10.79 years (SD = 1.18). Two questionnaires were used: Perception of Similarities and Differences Test for attentional capacity and the KIDMED questionnaire to assess diet quality. Weight status was assessed by body mass index (kg/m²) adjusted for sex and age. Statistical analysis showed no significant differences according to sex, diet quality or weight status (p > .05, for all), except for the number of errors (p < .05) and inhibitory control (p < .05), in favour of normal-weight schoolchildren. In conclusion, having an optimal weight status may be related to better inhibitory control and fewer attentional errors than their overweight peers. Therefore, health promotion professionals in school settings should consider the positive role that optimal weight status can play in care; and initiate programmes to promote healthy eating among school children.

Introduction

Basic education is a host of stages (nursery, primary and secondary) that are critical for cognitive development, as the brain’s neuroplasticity is greater at this age (Rueda et al., 2015). The brain is the organ of thought, defined as the faculty of conceiving, judging or inferring, or considering something, an opinion or a set of ideas on a given subject, and includes learning processes (Bueno-Torrens, 2020). Cognitive function is important due to the fact that this metacognitive process is necessary for performing schoolchildren’s complex and goal-oriented learning operations (Akubuilo et al., 2020). Cognitive skills are those that involve the processing of information and the ability to use it later (Caamaño-Navarrete et al., 2021). According to this study, these include various capacities such as perception, comprehension, memory, language and attention, among others. 

Both brain formation and function and neuronal plasticity are influenced by the activity of a set of genes and also by epigenetic modifications, which contribute to the regulation of gene expression, adapting it to environmental conditions (Bueno-Torrens & Forés-Miravalles, 2018), which in turn can lead to structural and functional brain changes early in life (Polverino et al., 2021). Therefore, understanding the weight of environmental factors in the modulation of cognitive functioning is relevant for possible interventions in the educational context.

In this regard, lifestyle may be associated with cognitive functions (González-Calvo et al., 2022; Tapia-Serrano et al., 2021). For example, high rates of obesity indicate that food intake is not limited to eating in response to the biological need for energy, but has cognitive and socio-emotional triggers, such as eating due to anxiety, boredom or other emotions (Carrillo-López & García, 2020). Diet has also been identified as one of the main nutritional factors contributing to the prevalence of non-communicable diseases, including neurodegenerative disorders (Godos et al., 2020). Dietary polyphenols, antioxidant components and anti-inflammatory agents in plant-rich diets have been shown to modulate neuroinflammation, adult neurogenesis and brain signalling, all of which are related to cognitive function (Nyaradi et al., 2013). The Mediterranean diet is internationally recognised as healthy, characterised by an intake of a large amount of vegetables, fruits, bread or other forms of grains, rice and includes virgin olive oil as the main source of fat, moderate amounts of dairy products (essentially cheese and yoghurt), as well as moderate amounts of fish and red meat (García-Cantó et al., 2019). This Mediterranean dietary pattern is presented not only as a cultural model but also as a healthy and environmentally friendly one (Serra-Majem & Ortiz-Andrellucchi, 2018). This study shows that recognition by UNESCO, with consequent greater visibility and acceptance of the Mediterranean diet worldwide, together with better and more scientific evidence on its benefits and effectiveness in longevity, quality of life and disease prevention, have led to this dietary pattern being fully recommended at all stages of life. 

While there is extensive research in animals to describe the relationship between individual nutrients and brain development and function, there is limited evidence on the effect of diet on cognitive function in humans (Jirout et al., 2019). This study shows that total diet quality intake patterns may be unfavourable for cognitive function in ageing (e.g. Western diet has been linked to accelerated brain ageing). For their part, Caamaño-Navarrete et al. (2021) have highlighted that there are moderate correlations for dietary intake characterised by regular breakfast consumption, lower intake of energy-rich and nutrient-poor foods and overall diet quality with respect to cognitive ability. Furthermore, a cluster analysis study showed that schoolchildren with better lifestyles have better cognitive ability (Dumuid et al., 2017). 

Within education, attentional capacity has been identified as one of the top variables with the highest rate of impairment (around 15%) (Llanos-Lizcano et al., 2019). Attention serves to capture information and has been defined as a basic cognitive mechanism responsible for selecting, processing and prioritising the information necessary to perform any task, as well as focusing mental processes towards any stimulus that occurs in the environment, in addition to excluding information that is irrelevant for the development of the task (Rueda et al., 2015). Thus, according to this study, attention is the ability to generate, direct and maintain a state of activation adequate for the correct processing of information. 

Jirout et al. (2019) indicate that current knowledge about indicators of cognition and optimal attention is incomplete and probably lacks understanding of many critical facts and relationships, their interactions and the nature of their interrelationships, such as the existence of differentiating factors that could provide broader knowledge to increase the effectiveness of educational interventions focused on improving attention. 

Based on these precedents, it is important to analyse the association between healthy lifestyle indicators, such as diet quality and weight status, with attentional capacity. Furthermore, according to the scientific literature consulted, no other research has analysed the association of attentional capacity with these indicators in Spanish schoolchildren in the early stages of schooling. Therefore, the aim of this study was to analyse the relationship between weight status and diet quality with attentional capacity in primary school children. 

Methodology

Design and Participants

A total of 209 schoolchildren (125 boys and 84 girls) from the Autonomous Community of the Canary Islands (south of Tenerife), aged between 10 and 12 years (SD = 1.18) participated in this descriptive, cross-sectional, empirical ex post facto study (see Table 1). Sampling was non-probabilistic, non-random, convenience sampling (access to the sample). 

Table 1

Distribution of frequencies (and percentages) considering gender and academic year.

See table

Two public schools were selected in the Adeje and Arona districts. These schools have a medium-high socio-economic level. In previous meetings held with the school leadership teams and legal guardians of the schoolchildren, they were informed of the study protocol and informed consent was requested for the schoolchildren to participate. Inclusion criteria were: being between 10-12 years of age and regular school attendance (90% of classes during the months of the current academic year). The following exclusion criterion was also considered: I) Failure to provide informed consent to participate in the research. It should be noted that, after jointly estimating the relevant statistics (units of variables and effect size) for the calculation of the sample size (population = 921), it was determined that the minimum sample should be a total of 198 participants to ensure that the results of the study would be consistent (Quispe et al., 2020); and this was achieved, as there was a total sample of 209 students. 

Procedure

The study was carried out during May and June of the 2020/21 academic year. The team consisted of a main researcher investigator and two collaborating doctors (professors specialising in primary education and physical education). A theoretical session was held with each study group prior to the completion of the questionnaires in order to ensure that all participants understood them. The researchers administered the tests in their normal classroom groups. The questionnaires were administered during the first school period in order to avoid possible fatigue from the school day and to interrupt the school dynamics as little as possible. 

The research was conducted in accordance with the ethical standards recognised by the Declaration of Helsinki (2013 revision). This work has been assessed and approved by the Bioethics Committee of the University of Murcia (Murcia, Spain) from the ethical point of view of research (Code: RUxFMqw2-WMQUy9wq-vYPTQUIM-xg/kY4cF).

Resources

Causal or Independent Variable

The quality of the Mediterranean diet was measured using the KIDMED questionnaire (Serra-Majem et al., 2004), which has been widely used in education (Henriksson et al., 2017; Tapia-Serrano et al., 2021). In its original version, a reliability coefficient of .93 was found. This instrument is composed of 16 items representing standards of the traditional Mediterranean diet. Four of them are scored negatively (-1 point) if answered positively (items 6, 12, 14 and 16), while the remaining twelve items are scored positively (+1) if answered positively. After calculation, an overall score of between -4 and 12 is obtained, which indicates a better or worse diet quality. Following the recommendation of the original study, in this study diet quality was categorised into improvable ≤ 7 and optimal ≥ 8 diet quality, as has been done in other previous studies (Carrillo-López & García, 2020; García-Cantó et al., 2019). 

Weight and height were determined using an electronic balance (TANITA TBF 300A, USA) and measuring rod (SECAA800, USA) with an accuracy of 100g and 1mm, respectively, following the protocol of the International Society for the Advancement of Kynanthropometry (ISAK) with level I certified personnel. From these anthropometric variables, body mass index (kg/m²) was calculated and age and sex-adjusted nutritional status was determined (Cole & Lobstein, 2012). Participants were categorised into two groups: normal weight and overweight (overweight + obesity), as has been done in previous studies (Carrillo-López & García, 2020; Tapia-Serrano et al., 2021).

Criterion or Dependent Variables

Selective attention was estimated using the thirteenth version of Thurstone & Yela’s (2012) Perception of Similarities and Differences Test (Faces-R). This test measures the ability to perceive, with the quickest processing speed, similarities, differences and partially ordered stimulus patterns. It is used for participants aged 6 to 18 years. It consists of 60 graphic elements, each of which is made up of three schematic drawings of faces with the mouth, eyebrows and hair represented with elementary strokes. In each set of three faces, two are the same, and the task is to determine which is different and cross it out. The participant has a total of three minutes. The score is obtained directly from the total number of correct answers, with a maximum score of 60 points. 

Test-retest reliability studies by Crespo-Eguílaz et al. (2006) with individuals aged six years and older showed a reliability coefficient of .89. Taking these aspects into account, the following variables were considered in this research: (1) Correct Answers (A): total number of correct answers; (2) Errors (E): number of incorrect answers; (3) Omissions (O): figures not indicated in the task; (4) Inhibitory control (IC): ratio of the difference between correct and incorrect responses, divided by the sum of correct and incorrect x 100 ((A-E / A+E) x 100); (5) Attentional efficacy (AE): is the number of correct answers divided by the number of correct answers plus errors plus omissions x 100 ((A / A+E+O) x 100).

Statistical Analysis

Normality and homogeneity of variances were obtained using the Kolmogorov Smirnov and Levene statistics, respectively. As a normal distribution of the recorded values was observed, a parametric analysis was chosen. Differences in the different study variables according to sex (males vs. females), weight status (normal weight vs. overweight) and diet quality (improvable vs. optimal) was carried out using the t-Student test. Effect size was calculated using Cohen’s d (.20 = small; .50 = medium, and .80 = large effect). The differential analysis of the combined weight status/diet quality variable, which resulted in 4 groups (normal weight/optimal DQ, normal weight/improvable DQ, overweight/optimal DQ, and overweight/improvable DQ, was studied using a simple analysis of variance (one-way ANOVA; Bonferroni’s post hoc test). It should be noted that Bonferroni correction was applied to reduce the risk of a Type 1 error in multiple testing; the p value was p < .01. Effect size was calculated using η² (.01 = small; .06 =  medium, and .14 = large effect) (Cumming & Calin, 2016). A bivariate correlation analysis was performed between attention, body mass index and diet quality (Pearson’s test). Data analysis was performed using IBM SPSS 25.0 statistical software and the significance level was set at 5% (p ≤ .05).  

Results

Table 2 shows the scores obtained in the different variables of the study according to sex. It should be noted that no significant differences were found for any variable according to sex (p > .05). 

Table 2

Scores obtained in the different variables of the study according to gender.

See table

Table 3 shows the different bivariate correlations observed according to body mass index, diet quality and factors and global index of attention. No statistically significant positive or negative correlation was found between the factors and the overall index of attention and diet quality (p > .05 for all). However, a significant negative correlation was found between inhibitory control and body mass index (p < .05). 

Table 3

Bivariate correlation between body mass index, diet quality and attention. 

See table

When analysing the differences in the responses of the dimensions of attention considering weight status (see Table 4), significant differences were only found in the number of errors (p < .05) and in the inhibitory control (p < .05), in favour of those at normal weight.

Table 4

Differences in attention according to weight status.

See table

On the other hand, when analysing the differences in detail considering the quality of the diet classified as improvable vs. optimal (see Table 5), it is worth noting that no significant differences were obtained for any variable of attention (p  > .05).

Table 5

Differences in attention according to diet quality.

See Table

In table 6, the joint relationship between weight status and diet quality with attentional capacity is shown. ANOVA analysis showed significant differences in the inhibitory control dimension (p < .05), in favour of those in normal weight/optimal QD relative to those who are overweight/optimal QD. Despite the non-significance, it is observed that those schoolchildren with better weight status and optimal diet quality obtain, for all dimensions, better levels of attention than their overweight peers and those with poor diet quality. 

Table 6

Differences in attention according to weight status and diet quality.

See Table

Discussion 

The aim of this study was to analyse the relationship between weight status and diet quality with attentional capacity in primary school children. The main findings show that schoolchildren with a normal weight status have better inhibitory control and fewer attentional errors than their overweight peers. However, the absence of a statistically significant relationship between diet quality and attentional capacity is surprising, since weight status is obtained from the energy balance of nutrients ingested in the diet minus caloric expenditure and is measured by indicators such as body mass index for age and sex, which allows for the diagnosis of being overweight or obese (Cole & Lobstein, 2012).

Since no studies in primary school children have been found among the scientific literature that analyse the association between weight status and attention, this prevents us from making direct comparisons. Furthermore, studies analysing the relationship between diet quality and attention are very scarce in primary school children, hence the original focus of our study. Scientific literature found on primary school children (Henriksson et al., 2017; Caamaño-Navarrete et al., 2021) suggests that healthier dietary patterns, as indicated by a higher diet quality index, are associated with attention span. In turn, similar studies in terms of methodology show a lack of relationship between weight status and cognitive variables such as intelligence level (Akubuilo et al., 2020) or other variables such as academic performance, where no significant relationship between eating habits and academic performance or nutritional status has been found (Iglesias et al., 2019). 

These results can be explained on the basis of Information Processing Theory and human physiology, as it has been hypothesised that the potential role of the “gut-brain axis” in the human body is of critical importance for the proper functioning of the human body (Jirout et al., 2019). That is, physiological conditions, such as the nutrients and energy provided by meals and snacks, as well as the resulting feelings of hunger or tiredness, can directly influence the capacity for cognitive processes. This study reflects that the learning process is a complex construct that can be described as a series of engagements in information/memory processing and storage systems that ultimately result in knowledge. One of the most basic conditions for a schoolchild to be able to pay attention to a task is to have the necessary energy and no discomfort inhibiting factors (e.g. hunger or fatigue). If conditions are not optimal, the schoolchild experiences lower levels of alertness or vigilance, thus decreasing attention to any input from the environment. Therefore, attention span will be restricted, limiting the information that is eventually encoded and retained in long-term memory, from where it can be retrieved later (Nyaradi et al., 2013). 

Further hypothesising the potential role of the “gut-brain axis” and its effect on modulating systemic inflammation and oxidative stress, there are molecular mechanisms underlying the putative beneficial effects on brain health of different dietary factors, such as I) micro- and macronutrient intake and habits, such as meal timing and circadian rhythm; II) the role of hormone homeostasis in the context of glucose metabolism and adiponectin regulation and its impact on systemic and neuroinflammatory inflammation, and III) individual bioactive molecules that exert antioxidant activities and act as anti-inflammatory agents, such as omega-3 fatty acids and polyphenols, considered beneficial to the central nervous system through modulation of neurogenesis, synaptic and neuronal plasticity and microglia activation (Godos et al., 2020).

For example, lutein, one of the three main types of dietary carotenoids, has been reported to be present in the brain, and metabolomic analyses indicate that it has “functional significance” in cognition and development in the infant brain (Jia et al., 2017). Lutein concentration correlates with homocarnosine, a neuroprotective antioxidant found in the hippocampus and frontal cortex. Interestingly, the concentration of lutein is higher in schoolchildren than in adults, suggesting a possible role in development. In particular, lutein has been specifically linked to cognitive function measures of executive function, language, learning and memory, and improves temporal processing speed (Reichelt & Rank, 2017). In turn, the study by Godos et al. (2020) hypothesised that flavonoids affect the production, bioavailability and biological activity of metabolites related to the gut-microbiome-brain axis. An imbalance of the gut microbiota is associated with a local and systemic inflammatory state, which in turn can affect immune and nervous system related diseases. Specifically, a higher inflammatory state triggers vascular damage and neuroinflammation, which in turn can cause alterations in brain structure and function, including ionic homeostasis, regulation of metabolic functions, production of antioxidant species, synaptic glutamate levels, modulation of synaptic plasticity and, ultimately, maintenance of the blood-brain barrier, systemic inflammation and oxidative stress and cognitive impairment (Ceppa et al., 2019). In this regard, higher dietary intake of flavonoids (fruits and vegetables are rich in flavonoids) and certain subclasses are associated with better cognitive health (Bleiweiss-Sande et al., 2019). In particular, according to this study, higher dietary intakes of catechins, flavonols, anthocyanins and, among individual molecules, quercetin, are positively associated with cognitive status. 

In turn, it has been suggested that the effects of various nutrients on diet-dependent epigenetic processes, in particular DNA methylation and histone post-translational modifications, and their potential role as a therapeutic target, may describe how some forms of cognitive decline could be prevented or modulated from early life onwards (Polverino et al., 2021). In this respect, diet may lead to alterations in dopamine-mediated reward signalling and controlled inhibitory neurotransmission by γ-aminobutyric acid (GABA), two major neurotransmitter systems that are built up during the infantile-adolescent period. In this sense, poor dietary choices can derail the normal maturation process and influence neurodevelopmental trajectories, which may predispose schoolchildren to dysregulated eating and impulsive behaviours that affect attention (Reichelt & Rank, 2017). 

This is evidenced in a study with schoolchildren where they found that eating breakfast just before a cognitive demand, and having a regular high quality breakfast, is associated with increased attentional capacity (Peña-Jorquera et al., 2021). Similarly, it has been observed that those who report greater adherence to the Mediterranean diet have higher scores in elaboration and organisation strategies; critical thinking and study habits; greater effort capacity; self-regulation and intrinsically oriented goal setting (Dumuid et al., 2017). 

Future studies should shed further light on the findings, as the difference in results across the body of research on these relationships may be a consequence of how attention, diet quality or weight status are measured or quantified (Carrillo-López & García, 2020). Therefore, these findings should be interpreted with caution due to the fact that this study was not interventionist, but based on self-reported data, with unknown quality and quantity of food consumed daily by schoolchildren. Similarly, no cause and effect relationship between attention and weight status or diet quality can be inferred in this study. In addition, there are confounding factors not considered in this study that are likely to influence these relationships (such as physical condition, screen time or hours of sleep) (Jiménez-Parra et al., 2022; Sebastiani, 2019). Therefore, these differential effects might be related to environmental aspects and deserve to be further investigated in future studies. 

Conclusions

In conclusion, the present study contributes to the scientific literature investigating the relationship between healthy lifestyle habits, such as diet quality or weight status, and the outcomes of cognitive processes, such as attention. Based on these results, it is concluded that having a healthy weight status may be related to better inhibitory control and fewer attentional errors than their overweight peers. In the meantime, health promotion professionals in school settings should consider the positive role that optimal weight status can play in care; and initiate programmes to promote healthy eating among schoolchildren.

Acknowledgements

We thank the schools for opening their doors to us and the participants for taking part in this study. Without you, scientific work would not be possible.