Ethical considerations

Our university's institutional review board approved this study. To protect participants' identities, we did not collect identifying information. Participants were not compensated for their time.

Subjects

The observational, descriptive, retrospective, and correlational research study was carried out on the infant student population from 9 to 13 years of primary school "Lic. Presidente Miguel Alemán" of the morning shift located in the municipality of Tepic, Nayarit Mexico. The groups of school children were listed, which was made up of 226 total students, fourth grade (78 students), fifth grade (93 students), and sixth grade (55 students). The sampling was carried out in a single stage in the months of June 2018, whose objective was to identify the relationships of EH and NS in school children. To carry out the study, authorization was requested from the management of the elementary school, parents' society, and the parents or guardians of the children subject to the study. Informed consent specified exclusively the carrying out of measurements of weight, height, and BMI, as well as the implementation of an anonymous questionnaire on lifestyles in terms of nutrition and exercise in and out of elementary school, for which was selected based on the Institute of Epidemiology and Health Care, and some questionable ones that have been published¹⁶-¹⁸. Parents were invited to answer the questionnaire during the school schedule to ensure that they were answered by themselves and not by other relatives. A written request was made to the teacher of each group for 45 min of class time, once a week and the presence of the parents for the application of the questionnaire.

Questionnaires

A questionnaire was developed for parents and a questionnaire about their child, to be filled in together. These questionnaires included questions about parents' availability to prepare lunch before taking their children to school, food preferences at breakfast, food preferences of children within the school, and physical activities (PA) of children during and after school.

The food preferences were calculated as a semi-quantitative index using a scale for the frequency of eating (FE, range 0-3) and another for the usual amount of intake (AI, range 1-3). The preference index (PI) was calculated by multiplying these two amounts: FE × AI (range 0-9). The index will be close to 9 if a specific food is consumed frequently and in large amounts during a week, while it will be close to 0 if a food is consumed rarely or in small amounts. This questionnaire is semi-quantitative because it allows information to be obtained on the pattern of habitual consumption; in addition to being a cheap, quick, and easy to apply method, it does not alter the habitual consumption pattern of children and allows information to be extracted on the influence of the variability of consumption of types of food. Likewise, this type of questionnaire is capable of classifying individuals according to their EH. The EH questionnaire for children before and during school entry was expressed as the frequency of consumption of the food groups without establishing rations or quantities, not for the purpose of converting food into nutrients but to find out the pattern of EH using the data as estimates of the average frequency of consumption of the different foods. Regarding PA, the information requested is related to the practice of PA, the nature of the activity or its frequency and aspects related to sedentary activities by the students. The analysis of the data from the questionnaires was performed using absolute and relative frequencies of each food, parental decision, and PA during for the total number of children.

Level of physical activity

For this study, the International Physical Activity Questionnaire for Children's¹⁹ was used, which is applicable to children and allows us to obtain comparable estimates of the PH that children carry out during the school day, making it possible to list the different types of PH in school children, taking into account that they do not provide an estimate of caloric expenditure. PH level items were evaluated with a frequency scale (0, 25, 50, 75, and 100%).

Anthropometric measurements

Students were measured weight, height, and percentiles. Students wore underwear. Weight was measured to the nearest 0.1 kg using a digital scale (Omron HBF-514C, USA) with a capacity of 150 Kg. Height was measured using a wall-mounted stadiometer (Seca, model 786, Germany) to the nearest 0.1 cm. BMI was calculated as weight (Kg) divided by height (m) squared. Data analysis was performed using absolute frequencies by NS (normal, malnutrition, overweight, and Ob).

Analysis

For the study of the descriptive parameters, percentages were used to describe all the variables of the study; likewise for the study of the comparative type between degrees, contingency tables, independent samples t-tests, and ANOVA with the statistical package Statistica v10 (Stat Soft. Inc., Tulsa, OK, USA). The level of statistical significance used in all cases was p < 0.05. To carry out the analysis, a weighting factor was applied, which allowed the proportionality of each stratum to be kept in relation to the real distribution.

Parents' influence on children's breakfast

One aspect of paramount importance in the NS is the habits and EH, which are influenced by the environment where the children develops²⁰. The influence of the family environment is quite strong in the child stage because that is where it is decided which types of food can be bought and prepared according to the economic aspect, the availability of time, and the preferences for food selection²⁰,²¹. In our study, we saw significant aspects in the parents' decisions about their children's food. There is a positive trend among parents who prefer to give money to their children's last school grade (6^th) to buy something at school while their 4^th buy food at the tiendita for lunch (Table 1). These results are consistent with Savage²² which notes that family integration into a child's EA is greatest when the child is younger; while the age of the child tends to be more capricious. In addition, the availability of money allows them to buy food without parental control. It is important to give and account of the family context to the infant, as it identifies how the development of different EH that may benefits or affect the health of school children is influenced²¹. New generations of parents have stopped questioning what food they are buying for their children. Likewise, habits are behaviors that children adopt in their lives from a family member or group of friends²⁰,²³. It is highly worrying to see more children who are having this disease due to lack of information from their parents and also because they make decisions without conscience and responsibility in their EH. It is worth nothing, the grandparents or great-grandparents did not have this type of disease, it was not common to hear about Ob because the diet of Mexicans was different way, because they only ate what Mexico produce²³,²⁴. In contrast, since the Free Trade Agreement that has allowed the entry of companies selling high processed foods, the health of infants has been put at risk because these foods have been found to have excess calories and other substances harmful to their health⁷. Therefore, it is not a question of stopping the consumption of the packages but of trying to inform oneself and improve the habits of the parents for the betterment of the habits of the children. Similarly, it is strange to demand from children about eating well, not spending money on junk food if they do not have or follow an example from their parents and it will be very difficult for them to consider it as a habit, as well as PA, it sound incongruous to ask and not do it. It is worth nothing that some school children commented that they come from families with low food availability and they can eat three meals per day but with limited consumption and preparation, as well as in nutritional quality. This type of population eats breakfast (bean 10-26%], eggs [48-51%], tortillas [88%], and coffee 25-41%]), and sometimes they have to sacrifice breakfast to eat the food (1-8%, Table 1). There was no significant difference and very few children who do not usually eat breakfast (Table 1). Therefore, it is important to emphasize that not having breakfast implies in the cognitive function of children²⁵. These children's lunch is also precarious and in many cases consists of a slice of roll with scrambled egg and ham or beans.

On the other hand, it is very important the feeling habit in the child since it begins to generate the acceptance to a food or the rejection, although it is certain that in the food election there are biological determinants or genetic predispositions such as innate preference by sweet tastes and aversion to bitter tastes, which the vast majority of preferences and rejection learned in the process at this stage. In general, when asking the school children what the food they preferred, they referred to food that commonly no consumes at home (hamburgers, hot dogs, candies, soft drinks, cookies, pizza, and others). In particular, children with high economic availability have a high tendency to taste fried foods, candies, and others that they acquire in the school store (tiendita) or in the surrounding area. It was surprised to observe a significant difference in burger consumption between school grades, with the highest frequency of consumption being among 6^th (PI = 6). It was also striking to observe that soft drinks and sweets had a greater preference (PI = 9) than natural juices and bottled water, which had no preference at all. The School Health Survey 2008 placed Mexico in the first place of consumption of soft drinks and among the five most consumed products in primary and secondary public schools in the country²⁶. The 2016 Midway National Health and Nutrition Survey (ENSANUT) indicated that 81.5% of school children (5-11 years) consume caloric beverages²⁷. Therefore, there is a significant percentage of the school population (Table 1) who tend to "eat breakfast" at school which is deficient in quantity and quality, thus predisposing them to a high consumption of fats and carbohydrates that cause an increase in adipose tissue⁷,²⁰,²⁵.

Physical activity of school children

During recess, food, and drink intake is integrated into a variety of activities (talking, playing, walking, and sitting) that children engage in, some alone, most in groups. Although a general trend could be observed associating, on the one hand, greater food consumption by girls in the context of "quiet" games, slow walks in the playground and conversations, and on the other hand, less food consumption by boys involved to a greater extent in games, soccer being a game that summons, and identifies most boys. We were also able to observe a significant difference and increasing trend in how children prefer to sit as they progress through the grades (Table 4). The results show that physical inactivity by the children of 6^th (33%) is maintained regardless of the sex or NS of the children. However, games during recess are centrally influenced by the characteristics of the spaces, the availability of elements (ropes, elastics, balls, and others) provided by the school or carried by the children and, above all, by institutional rules (principals and teachers) regarding permitted games, which generally restrict games with movement (soccer, stains, hide-and-seek, poliladron, and others) to preserve the physical integrity of the students and prevent accidents. In this sense, it was striking how, despite the prohibition of playing soccer in almost all of the school, children recreate scenes of this game using a variety of elements such as balls (empty bottles, caps, paper buns, and others). It is, therefore, important to pay attention to the type of play in the playground, not only because for many children it is one of the few spaces available for physical-recreational activities on a daily basis but also because the type of play is related to greater or lesser food consumption. Because of these restrictions, the PA of most Mexican school children (Fig. 3)²⁸,²⁹. This effect leads to a higher prevalence of Ob in 6^th grade school children (Table 5). This finding was similar to that reported in the WHO²⁶ where > 80% of school children did not comply with the recommendation, which resulted. This data are alarming given the relevance of PA for health in childhood that will last until adulthood. Numerous studies point to a progressive decline from physical-sports practice as one moves from childhood to adolescence²⁹-³¹.

In Mexico, research has evaluated the intensity of physical activity in primary school physical education and recreation classes and has found that about 70% of the total time spent in physical education class is used for physical activity instruction and 30% for exercise³². These results are consistent with the comments the children made to us that the large amount of time spent standing while the teacher organizes the group is long lines (> 30 school children) and class time was running out and not enough to play. According to the Mexican Report Card for Physical Activity in Children and Youth³³, an instrument for monitoring children's PH, Mexico is not providing adequate opportunities for PH across its different domains, mainly in school. The picture is even more alarming considering that most primary schools are surrounded by high-energy foods (discussed below).

The results obtained in our study show a higher prevalence of overweight and obesity compared to those reported in Paraguay, Chile and Brazil (Florianópolis)³⁴-³⁶. Our results are also consistent with studies conducted with Spanish children where they showed that 57.5% of young school children are inactive at recess³⁷. Our study is consistent with the WHO study where it was reported that 62% of school children are not enough in PH within the school³⁸. The result is consistent with another study with Spanish elementary school children that showed 70% of children to be insufficiently active³⁹. In our study, data on PH were similar to those reported in other countries such as Colombia and Mozambique⁴⁰,⁴¹, which noted that PA may be related to the lack of space, facilities, opportunities, equipment, and human resources within school premises, making it difficult for children to engage in any sport during school hours. In addition, many elementary schools in Mexico have two shifts, which reduce opportunities for extracurricular PA. In addition, the time allocated to physical education, leisure, and recreation in schools, especially in elementary schools, has declined to give greater priority to theoretical disciplines⁴². This has increased children's sedentary activities which can make a crucial contribution to their health³⁰. Therefore, there are numerous studies that agree to show positive changes with PA and that it has been linked to a reduction in the risk of suffering from more than 25 chronic health conditions²⁹,³⁰,⁴³. Seeing this effect, schools should provide more and better PH opportunities to children and adapted to their basic needs³⁸. It is also necessary to ensure that schools contribute at least twice a week of varied and enjoyable PH to improve, maintain and develop children's lifelong PA habits⁴⁴. It should be noted that most elementary schools in Mexico have playgrounds that are poorly equipped for PA and active play, and should, therefore, be maintained and better equipped. Thus, variety of programs have been implemented in Mexico to foster PH within the school environment³⁴. To date, the impact of this intervention is unknown, so it is impossible to attribute the increase in sports activities among school children. It is worth mentioning that there is currently no definitive evidence on PA carried out by children during school time in Mexico; likewise, the amount of caloric expenditure, the intensity of the duration of PH and its relationship with health and nutrition parameters, gender, age or school grade and socio-cultural, and economic environment is unknown.

NS of school children

The results of this research present remarkable evidence of weight gain in children, with a significant difference between NS at each grade level. This is directly related to the inadequate food preferences that children acquire in school, as it is a very important factor in the appearance of child Ob; coupled with the quantity, continuity of consumption and quality of food⁴⁴. Evidence also suggests that it is a lack of commitment by parents to their children's health. The results obtained with the school children population not only explain the index of Ob but also coincide with researches, in terms of the risk of chronic non-degenerative diseases since the habits and attitudes that will predominate throughout life are formed in the school stage⁵,⁷,²⁰,³⁶,⁴⁰. The sedentary habits incurred by this population cannot be ignored, which is why it coincides with some studies carried out in Mexico where they investigated the prevalence of overweight and Ob, as well as recognized risk factors related to these pathologies, such as EH when watching TV, taking a nap after eating, watching TV after eating, chatting with the cell phone while lying down or sitting down, and others⁴⁵,⁴⁶. The fundamental cause of Ob is an energy imbalance between calories consumed and spent¹. Around the world, an increase in the intake of high-calorie but micronutrient-poor foods is prevalent, as well as a decrease in PA, as a result of the increasingly sedentary nature, including new modes of travel (car, public transport, and shuttle service [uber and taxi]) to get children to school²,⁴,⁷. Furthermore, the nutritional transition that Mexico is experiencing is characterized by a westernization of the diet, specifically: (1) an increase in the availability of low-cost junk food with high amounts of calories and salt; (2) a decrease in the time available for food preparation at home; (3) a significant increase in the exposure to advertising and the supply of industrialized foods; and (4) a decrease in the population's PA. Thus, in the present investigation these causes were observed that harm in a way the health of the infants. The high incidence of Ob, which is alarming figures, so it is possible to conclude that in Mexico there, is no public policy to promote EH and PH, which is necessary to implement strategic health programs in basic schools to reduce this problem in children. In addition, the influence of parents on NS is essential to meet the basic needs of the child, who's inadequate EH and PA from childhood will be a reflection of their future health condition. It is important to implement nutrition education in schools o establish healthy choices for children and set goals, including: (1) promoting PA in the school environment; (2) reducing the consumption of sugars and other added caloric sweeteners in food and beverages; and (3) increasing the daily consumption of fruits and vegetables, legumes, whole grain cereals, and fiber in the diet.