Association between breakfast omission and abdominal adiposity in low-income adolescents

Objective To assess the association between breakfast omission, overweight/obesity, abdominal adiposity, and unhealthy lifestyle of low-income adolescents. A cross-sectional population study involving 571 public school students aged between 15 and 19 years old. The habit of having breakfast was assessed using a form, checking the weekly frequency of a given meal and considered as breakfast omission when these adolescents did not have breakfast for at least 5 days in the past week. Sociodemographic and lifestyle variables (sedentarism, physical activity level, and sleep duration) were also assessed. Overweight/obesity was defined as a body mass index above a Z-score of +1, and the presence of abdominal adiposity was determined by a waist circumference/height ratio greater than 0.5. The association between breakfast omission and lifestyle variables was assessed using the chi-square test and a multivariate logistic regression of the anthropometric indicators. The omission of breakfast was found in 31% of the adolescents and was associated with physical inactivity ( p <0.001). Regarding anthropometric indicators, breakfast omission was an independent factor for determining abdominal adiposity, with a 1.8 times greater chance of having this condition among those who omitted breakfast ( p =0.037). Omitting breakfast was frequent among the students assessed, and was associated with abdominal adiposity, a cardiometabolic risk factor. Investigation and early intervention are fundamental to change this behavior.


A B S T R A C T Objective
To assess the association between breakfast omission, overweight/obesity, abdominal adiposity, and unhealthy lifestyle of low-income adolescents. https://doi.org/10.1590/1678-9865202134e190245 2 ARAB RIBEIRO et al.

Methods
A cross-sectional population study involving 571 public school students aged between 15 and 19 years old. The habit of having breakfast was assessed using a form, checking the weekly frequency of a given meal and considered as breakfast omission when these adolescents did not have breakfast for at least 5 days in the past week. Sociodemographic and lifestyle variables (sedentarism, physical activity level, and sleep duration) were also assessed. Overweight/obesity was defined as a body mass index above a Z-score of +1, and the presence of abdominal adiposity was determined by a waist circumference/height ratio greater than 0.5. The association between breakfast omission and lifestyle variables was assessed using the chi-square test and a multivariate logistic regression of the anthropometric indicators.

Results
The omission of breakfast was found in 31% of the adolescents and was associated with physical inactivity (p<0.001). Regarding anthropometric indicators, breakfast omission was an independent factor for determining abdominal adiposity, with a 1.8 times greater chance of having this condition among those who omitted breakfast (p=0.037).

Conclusion
Omitting breakfast was frequent among the students assessed, and was associated with abdominal adiposity, a cardiometabolic risk factor. Investigation and early intervention are fundamental to change this behavior.

I N T R O D U C T I O N
Adolescence comprises a phase of sudden changes in which individuals establish the bases for their health throughout adulthood, being so an opportune moment for carrying out interventions [1]. The contemporary lifestyle has contributed to an increasing number of people omitting breakfast and this behavior has been frequent among adolescents [2][3][4].
The omission of breakfast can have repercussions on several aspects of adolescent health, such as cognitive and academic performance, quality of life, well-being, and nutritional status, leading to the emergence of obesity and abdominal adiposity, conditions related to the onset of chronic non-communicable diseases in adulthood [4,5]. While most papers in the literature have assessed the association of the habit of omitting breakfast among young people with the occurrence of overweight/obesity, few assessed the impact of this behavior on abdominal adiposity, especially among Brazilian adolescents in which the scientific literature is still scarce and not conclusive [4][5][6][7][8][9].
In addition, most existing studies, when assessing this association, do not consider the presence of confounding factors such as lifestyle (physical activity, physical inactivity, and sleep) [4]. Based on these facts, this study aimed to verify the association between breakfast omission, overweight/obesity, abdominal adiposity, and unhealthy lifestyle of low-income adolescents.

M E T H O D S
A cross-sectional population study, conducted in state high schools between September 2012 and June 2013, in the city of Campina Grande (PR), Brazil. The study population consisted of students, between 15 and 19 years old, enrolled in public institutions in the urban area.
For the sample calculation, it was considered the total number of students enrolled (9,294 students distributed in 264 classes), an estimated proportion of 50%, a sampling error of 5%, design effect (deff) of 1.5 (correction factor for random sampling by conglomerate) and an increase of 3% for eventual losses or refusals. The estimated minimum sample, therefore, was 570 students. Considering, as previously verified in the pilot study, the average number of 15 students per class, 39 classes were drawn, distributed in 18 schools. Five hundred eighty-three adolescents were contacted, but there were seven exclusions and five losses due to the non-response to the assessed item. In the end, 571 individuals were assessed.
Anthropometric data were collected in duplicate, being considered the average value of the two measurements. To assess and categorize nutritional status, the Body Mass Index (BMI) was used, following the recommendations of the Ministério da Saúde (Brazilian Ministry of Health) [10]. The Waist-to-Height Ratio (WHtR) was used to characterize abdominal adiposity, being considered present when WHtR was greater than 0.5 [11].
The omission of breakfast was assessed using the same question adopted in the Pesquisa Nacional de Saúde do Escolar (National Adolescent School-based Health Survey) which aims to verify the consumption of healthy and unhealthy foods in the past weeks [3]. Cases of students who did not have breakfast for at least 5 days in the past week were considered as breakfast omissions. The sociodemographic variables assessed were sex, age, social class -according to the criteria of the Associação Brasileira de Empresa de Pesquisa (ABEP, Brazilian Association of Research Companies) -and maternal educational level complete years of schooling [12].
Regarding lifestyle, those who performed less than 300 weekly minutes of accumulated physical activity were considered inactive. Those who slept less than 8 hours a day were classified as having sleep deprivation [3]. Data analysis was performed using the SPSS software, version 22.0 [13]. The Chi-Square test was performed to assess the relationship between breakfast omission and sociodemographic, lifestyle, nutritional status, and abdominal adiposity indicators.
To test the independence of breakfast omission and other factors in determining obesity/overweight and abdominal adiposity in the adolescents, a univariate logistic regression was performed. Subsequently, a multivariate model was constructed using the forward method according to a decreasing Odds Ratio with the inclusion of variables that obtained a "p" equal to or less than 0.20 in the univariate analysis. To assess the fit of the model, the Hosmer-Lemeshow test was performed. A 95% confidence interval was considered for all statistical analyses.

D I S C U S S I O N
The results of this study reinforce the hypothesis that the omission of breakfast represents an independent factor for the presence of abdominal adiposity in low-income adolescents. In turn, this is considered an indicator of the presence of metabolic alterations, such as insulin resistance, and is included as part of the criteria for diagnosis of metabolic syndrome [14].
The prevalence of breakfast omission observed in this study was lower than that verified in the ERICA Study involving 74,589 students from 1,247 educational institutions, distributed in 124 Brazilian cities, being 45.3% in the Northeastern region of Brazil [2]. A systematic review involving 286,804 children and adolescents from different continents (Europe, North America, Oceania, Asia, and Africa) also found a wide variability in the prevalence of this behavior among the studies assessed (0.7% to 74.7%) [4]. This difference may be due to the type of population assessed and the variation in the criteria adopted to define the omission of breakfast.
The habit of omitting breakfast tends to be more present in adolescents than in children, in girls, and in those whose mothers have a lower educational level and purchasing power [2,4,15]. In the present study, however, there was no association between the habit of omitting breakfast and the socio-demographic variables assessed.
Studies point out that adolescents who omit breakfast also present other unhealthy lifestyle indicators [4,16]. In the present study, it was verified that those who did not have the habit of having breakfast had a greater chance of being inactive. Something similar was found in a study of British adolescents aged between 10 and 16 years old [17].
A Spanish study with more than 3,000 adolescent students showed that, although there is an association between obesity and physical inactivity, and between obesity and breakfast omission, there was no significant relationship between breakfast omission and physical inactivity [18]. This was also observed in the study entitled Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA), which involved 2,148 adolescents aged between 12.5 and 17.5 years old and residents of 10 European cities, in which breakfast was not associated with either sedentary time or physical activity [19].
In the present study, obesity/overweight as well as abdominal adiposity were more prevalent in those who omitted breakfast, but only abdominal adiposity was independently associated to the habit of omitting breakfast. The association between breakfast omission and overweight/obesity was found in 270,362 in of children and adolescents assessed (94.7%) through a systematic review study, however it is important to emphasize that most studies did not make adjustments for confounding factors such as sex, age, and lifestyle [4].
A meta-analysis involving 16 observational studies stated that the risk of overweight and obesity in children and adolescents who did not have breakfast was 43% higher than those who regularly did [9]. Some mechanisms have been proposed to explain this association: greater thermogenesis among those who have breakfast, and decreased satiety among those who do not have [9].
In this study, adolescents who omitted breakfast were 1.8 times more likely to have abdominal adiposity when compared to those who did not omit breakfast. Similar data were found in studies involving Australian and Iranian children and adolescents. The first one involved 3,884 individuals aged between 5 and 16 years old and verified a 1.7 times greater chance of presenting abdominal adiposity among those who omitted breakfast [20]. In the Iranian study, that involved 5,625 students aged between 10 and 18 years old, the chance of abdominal adiposity among those who omitted breakfast was a little lower, 1.4 times [8].
Abdominal adiposity, regardless of the presence or absence of nutritional state alterations, is more closely related to cardiometabolic complications in adolescence and to breakfast omission [21]. It is important to emphasize that this last condition can also be associated to the reduction of insulin sensitivity, since the ingestion of this meal has a beneficial effect on appetite regulation and also improves the glycemic response at the next meal, by providing an increase in insulin sensitivity [22,23].
One of the limitations of the study is the diversity of the concept of "breakfast omission", making it difficult to compare studies. In addition, factors regarding eating habits that can influence obesity risk, such as time to eat breakfast, the meal composition, the habit of eating or omitting other meals, as well as eating patterns, were not assessed in this study. It is also important to emphasize the limitations related to cross-sectional designs, and that it is not possible to establish a causal relationship between the omission of breakfast and the variables studied.

C O N C L U S I O N
Omission of breakfast was frequent among the students assessed and was associated with abdominal adiposity, which is considered an indicator of cardiovascular risk. The early identification and intervention to change this behavior can contribute to minimize the impact of chronic non-communicable diseases not only in the individual context but also in the collective.