Background
Obesity has been identified as one of the major threats to future public health [
1]. Of particular concern is the dramatic increase in childhood obesity, which has been observed in recent years, not only in high-income countries, but also in low- and middle-income countries [
2]. In fact, a recent review reported that the prevalence of childhood overweight and obesity increased by more than 45% between 1980 and 2013 worldwide [
3]. Excess body weight during childhood is a strong predictor of adult obesity [
4] and other health consequences such as type 2 diabetes and cardiovascular disease in adolescence and adulthood [
5]. Thus, it is important to combat obesity and identify the risk factors associated with it.
The benefits of breastfeeding in early childhood are well established in the literature [
6]. Breastfeeding is the recommended form of nutrition for the first few months of a children´s life. Data from a meta-analysis showed that breastfeeding was associated with a significant reduction in the risk for childhood obesity [
6]. Other studies, however, reported only weak or no association between breastfeeding and childhood obesity [
7,
8]. The inconsistent results suggest that the association between breastfeeding and children’s weight status may be moderated by several other variables [
9].
Obesity is a multifactorial disorder influenced by genetic, socioeconomic and lifestyle factors [
10]. Parental body mass index (BMI), children birth weight, and breastfeeding duration are factors that have been shown to increase the risk of childhood obesity [
9‐
11]. However, lifestyle indicators, such as moderate-to-vigorous physical activity, sedentary behavior may confound the association between breastfeeding, parents’ BMI and birth weight with the risk of later childhood obesity [
9,
10,
12]. Thus, the aim of this study was to verify the association between breastfeeding, parental BMI and birth weight with obesity indicators in children.
Results
There were no significant differences (p > 0.05) between the participants regarding parental BMI, birth weight and obesity indicators between those with complete data and those who did not answer the question on breastfeeding. The final sample size with complete data consisted of 402 (50.2% girls; mean age: 10.0 years [95%CI: 9.9; 10.1]) children. Sample characteristics are shown in Table
1 according to nutritional status categories. Based on nutritional status categories, most children were classified as eutrophic (58.2%) followed by overweight (20.9%) and obese (17.2%). Sex, age, race/ethnicity, annual family income, mother’s educational level, breastfeeding, sedentary time and light and moderate physical activity intensity were not statistically different between the nutritional status categories. There was, however, a significant difference between the nutritional status categories in terms of birth weight, parental BMI, WC and %BF (Table
1).
Table 1
Characterization [n (%) or mean (95%CI)] of the sample according to nutritional status
Sex [n (%)] | | | | | 0.106 |
Boys | 7 (46.7) | 114 (48.7) | 36 (42.9) | 43 (62.3) | |
Girls | 8 (53.3) | 120 (51.3) | 48 (57.1) | 26 (37.7) | |
Age [years; mean (95%CI)] | 10.0 (9.7; 10.3) | 10.0 (9.9; 10.1) | 10.0 (9.9; 10.1) | 10.1 (9.9; 10.2) | 0.748 |
Race/ethnicity [n (%)] | | | | | 0.856 |
White/caucasian | 13 (86.7) | 172 (73.5) | 63 (75.0) | 56 (81.2) | |
Black | 0 (0.0) | 15 (6.4) | 4 (4.8) | 7 (10.1) | |
Mixed | 2 (13.3) | 35 (15.0) | 12 (14.3) | 4 (5.8) | |
Others | 0 (0.0) | 12 (5.1) | 5 (5.9) | 2 (2.9) | |
Annual family income [n (%)] | | | | | 0.915 |
<R$ 19,620 | 6 (40.0) | 78 (33.3) | 27 (32.1) | 20 (29.0) | |
R$ 19,620–32,700 | 4 (26.7) | 61 (26.1) | 18 (21.4) | 18 (26.1) | |
R$ 32,701–58,860 | 2 (13.3) | 56 (23.9) | 23 (27.5) | 17 (24.6) | |
>R$ 58,860 | 3 (20.0) | 39 (16.7) | 16 (19.0) | 14 (20.3) | |
Mother’s educational level [n (%)] | | | | | 0.382 |
Incomplete high school | 10 (66.7) | 156 (67.7) | 54 (64.3) | 51 (73.9) | |
Complete high school/incomplete higher education | 5 (33.3) | 62 (26.5) | 25 (29.7) | 11 (15.9) | |
Complete higher education | 0 (0.0) | 16 (6.8) | 5 (6.0) | 7 (10.1) | |
Breastfeeding [month; mean (95%CI)] | 6.21 (4.34; 8.08) | 6.71 (6.28; 7.15) | 6.53 (5.74; 7.31) | 5.45 (4.55; 6.36) | 0.086 |
Birth weight [g; mean (95%CI)] | 2836.4 (2572.7; 3100.1) | 3159.0 (3084.6; 3233.4) | 3276.2 (3149.6; 3402.7) | 3321.5 (3193.5; 3449.5) | < 0.001 |
Maternal BMI [kg/m2; mean (95%CI)] | 23.8 (21.7; 26.0) | 24.9 (24.3; 25.4) | 27.6 (26.3; 29.2) | 27.8 (26.4; 29.2) | < 0.001 |
Paternal BMI [kg/m2; mean (95%CI)] | 25.3 (23.8; 26.8) | 26.9 (26.2; 27.6) | 28.9 (27.9; 29.9) | 27.5 (26.4; 28.6) | < 0.001 |
Children BMI [kg/m2; mean (95%CI)] | 13.5 (13.1; 13.8) | 17.0 (16.8; 17.2) | 21.5 (21.2; 21.7) | 27.0 (26.1; 27.9) | < 0.001 |
Waist circumference [cm; mean (95%CI)] | 54.2 (52.8; 55.6) | 60.5 (59.9; 61.1) | 71.3 (70.4; 72.3) | 83.6 (81.4; 85.7) | < 0.001 |
Body fat [%; mean (95%CI)] | 9.1 (7.1; 11.0) | 17.8 (17,2; 28.4) | 27.7 (26.7; 28.6) | 36.2 (34.2; 38.1) | < 0.001 |
Accelerometry [min/day; mean (95%CI)] | | | | | |
Sedentary time | 490.9 (456.1; 525.7) | 497.9 (488.8; 507.2) | 503.2 (488.1; 518.2) | 507.6 (487.4; 527.7) | 0.716 |
Light physical activity | 342.4 (322.1; 362.6) | 336.6 (329.4; 343.8) | 336.5 (323.3; 349.9) | 332.8 (318.9; 346.6) | 0.923 |
Moderate physical activity | 46.4 (36.9; 55.8) | 42.5 (40.1; 44.9) | 38.4 (34.9; 41.8) | 41.3 (37.6; 44.9) | 0.210 |
Vigorous physical activity | 19.9 (14.9; 25.0) | 19.7 (17.9; 21.4) | 15.0 (13.1; 16.9) | 13.7 (11.2; 15.3) | < 0.001 |
Moderate-to-vigorous physical activity | 66.2 (52.8; 79.9) | 62.2 (58.3; 66.1) | 53.4 (48.3; 58.5) | 54.5 (49.1; 59.9) | 0.023 |
Table
2 presents the results of the correlation analysis describing associations between breastfeeding, parental BMI and birth weight with obesity indicators (BMI, %BF AND WC). Significant and positive correlations were observed between breastfeeding, maternal as well as paternal BMI and the children´s BMI, %BF and WC. Birth weight was weakly and positive associated with BMI and %BF but was not associated with WC (Table
2).
Table 2
Analysis of correlation of independent and dependent variables of children and parents
BMI (kg/m2) | 1.00 | 0.921* | 0.900* | -0.132* | 0.320* | 0.173* | 0.165* |
Body fat (%) | ----- | 1.00 | 0.834* | -0.112* | 0.308* | 0.198* | 0.161* |
WC (cm) | ----- | ----- | 1.00 | -0.097* | 0.271* | 0.153* | 0.164 |
Breastfeeding (month) | ----- | ----- | ----- | 1.00 | 0.054 | 0.014 | 0.155* |
Maternal BMI (kg/m2) | ----- | ----- | ----- | ----- | 1.00 | 0.189* | 0.095 |
Paternal BMI (kg/m2) | ----- | ----- | ----- | ----- | ----- | 1.00 | 0.109 |
Birth weight (g) | ----- | ----- | ----- | ----- | ----- | ----- | 1.00 |
Table
3 shows the results of the multivariate linear regression analyses in which Model 1 included sex, age, race/ethnicity and annual household income as covariates and Model 2 additionally included sedentary time and moderate-to-vigorous physical activity. In Model 1, we found positive and significant associations of maternal and paternal BMI as well as birth weight with all obesity indicators (children’s BMI, %BF and WC). Furthermore, breastfeeding was positively associated with %BF. In Model 2, maternal BMI and birth weight were positively associated with all obesity indicators, independent of sex, age, race/ethnicity, annual household income, sedentary time and moderate-to-vigorous physical activity.
Table 3
Association (β; 95%CI) between breastfeeding, parents’ body mass index and birth weight and obesity indicators
Model 1a |
Breastfeeding (month) | 0.043 | -0.007; 0.095 | 0.083 | | -0.104 | -0.010; -0.198 | 0.030 | | 0.085 | -0.036; 0.203 | 0.149 |
Maternal BMI (kg/m2) | 0.266 | 0.176; 0.366 | < 0.001 | | 0.512 | 0.310; 0.715 | < 0.001 | | 0.589 | 0.410; 0.772 | < 0.001 |
Paternal BMI (kg/m2) | 0.128 | 0.028: 0.263 | 0.031 | | 0.339 | 0.109; 0.600 | 0.008 | | 0.253 | 0.015; 0.535 | 0.060 |
Birth weight (g) | 0.003 | 0.001; 0.005 | < 0.001 | | 0.002 | 0.001; 0.004 | 0.003 | | 0.003 | 0.002; 0.005 | < 0.001 |
Model 2 b |
Breastfeeding (month) | -0.006 | -0.200; 0.188 | 0.954 | | 0.025 | -0.380; 0.430 | 0.904 | | -0.06 | -0.469; 0.457 | 0.979 |
Maternal BMI (kg/m2) | 0.228 | 0.142; 0.314 | < 0.001 | | 0.484 | 0.297; 0.671 | < 0.001 | | 0.509 | 0.304; 0.715 | < 0.001 |
Paternal BMI (kg/m2) | 0.083 | -0.028; 0.194 | 0.141 | | 0.256 | 0.021; 0.491 | 0.033 | | 0.183 | -0-078; 0.445 | 0.168 |
Birth weight (g) | 0.001 | 0.001; 0.002 | < 0.001 | | 0.002 | 0.001; 0.003 | 0.021 | | 0.003 | 0.001; 0.005 | < 0.001 |
Discussion
Obesity is a chronic inflammatory disease with a complex etiology that is related to social, environmental, behavioral, biological and genetic factors [
24]. Based on this, and knowing the importance of parents in this process, this study verified the positive association between parental BMI and birth weight with various obesity indicators during late childhood. Furthermore, breastfeeding was positively associated with %BF. After considering moderate-to-vigorous physical activity and sedentary time only maternal BMI remained remained a significant correlate of all obesity indicators. The main result showed positively association between maternal BMI and birth weight with all obesity indicators, independently of sex, age, race/ethnicity, annual household income, sedentary time and moderate-to-vigorous physical activity in the Model 2.
Breastfeeding has been increasingly studied in the context of preventing chronic non-communicable diseases during life, including the reduction in the risk of obesity [
9,
25]. Given the influence of the perinatal environment on future weight status recommendations for the prevention of childhood obesity encourage longer duration of breastfeeding [
26]. The present study found an inverse relationship between the number of months of breastfeeding and %BF (Model 1). Several studies also showed a possible dose-response relationship between the duration of breastfeeding and the risk of obesity [
9,
27]. However, our study, despite showing a significant association %BF, did not find it with other obesity indicators. As described by Ma et al. [
9] some studies that used only BMI as a measure for obesity also found no association between these variables, which may have underestimated the results. These inconsistencies reinforce the importance of using different indicators of obesity in future research to understand the factors associated with it. Possible mechanisms for protecting effects of breast milk against childhood obesity may also be related to nutritional and behavioral explanations. Breast milk has greater nutritional value and more balanced energy supply when compared to formula feeding, in addition to having more bioactive substances, such as leptin and ghrelin, which can influence the increase in body fat [
27]. In addition, it is likely that the introduction of other more caloric foods reflects the early replacement of breast milk with other foods.
The role of parents against obesity in their children extends from the first years of life, with breastfeeding, to childhood and adolescence, by encouraging and promoting healthy habits. Parents have a strong influence on the level of physical activity and diet of their children, with children’s behavior and diet shaped according to the conditions they are exposed to [
28]. The present study presented data that reinforces this concept, by showing significant associations between maternal BMI (Model 2) and all obesity indicators, independently of sedentary time and moderate-to-vigorous physical activity in children. Such findings can be explained by several reasons, from genetic predisposition to behavioral and exposure to common obesogenic factors (unhealthy diet) [
29].
With regard to combating childhood obesity, these findings reinforce the importance of parental involvement in interventions targeting childhood obesity that should already start during pregnancy and in the first years of life and continue throughout childhood and adolescence. The entire family needs to be aware of and take responsibility for future health outcomes as parent’s influence type and availability of various foods. They may also control the use of electronic equipment as well as offering family programs [
30].
Consistent with previous work [
29,
31], a linear regression (Model 2) that included school, sex, age, race/ethnicity, annual household income, sedentary time and moderate-to-vigorous physical activity, showed a stronger association between children´s BMI and maternal BMI compared to paternal BMI (β = 0.484 compared with β = 0.256). Furthermore, maternal BMI was significantly associated with all obesity indicators and paternal BMI was significantly associated with only %BF. A systematic review [
29] showed that it is premature to conclude that maternal and paternal weight statuses are equal risk factors for children´s obesity. According to the authors, another key factor to be measured is the timing of maternal and/or paternal overweight or obesity. It is probable that maternal obesity during some critical developmental period (e.g., pregnancy) might be more influential than maternal obesity during other periods [
32,
33]. Therefore, more rigorous studies should be conducted to compare the relative impact of paternal and maternal weight on children’s overweight or obesity during dissimilar developmental periods of the parental and childhood life course.
The present study also presented data related to birth weight, and the direct association between birth weight with all obesity indicators (BMI, BF%, WC; Model 2). There is a large number of studies that indicate a higher risk for obesity in children who are born both overweight (> 4 kg) and those who are born under the ideal weight (< 2.5 kg) [
34‐
36]. For instance, a meta-analysis of 66 studies from 26 countries demonstrated that high birth weight (> 4 kg) was positively associated with increased odds of childhood overweight (odds ratio: 1.66; 95%CI: 1.55; 1.77) compared to normal birth weight (< 2.5–4 kg) [
36].
Some limitations of this study should be considered when interpreting the results. The cross-sectional design that does not allow establishing a cause-and-effect relationship; the non-representative sample; the city chosen for the study is not compatible with the reality of Brazil; information obtained from a recall on birth weight and breastfeeding duration increases the risk of recall bias; and the use of a questionnaire to obtain information about parents’ weight and height for the calculation of BMI can generate information bias; although the accelerometers have been shown to be a valid tool to measure activity of all levels of intensity [
20,
21], the device cannot accurately capture various activities like upper body movements or cycling. The use of accelerometers to determine current activity levels in children along with the measurement of various obesity indicators, in addition to the quality of the procedures and methods in this study, on the other hand, are considerable strengths of this study.
Future studies, however, should consider more detailed information about pregnancy and breastfeeding, in addition to using more reliable instruments to obtain anthropometric values from parents. Furthermore, longitudinal studies that follow the evolution of growth and development of children with different durations of breastfeeding are needed. Finally, it should be remembered that the use of different obesity indicators must be considered.
Conclusion
We showed positive associations of maternal BMI and birth weight with obesity indicators, independent of sex, age, race/ethnicity, annual household income, sedentary time and moderate-to-vigorous physical activity. The encouragement of healthy lifestyle behaviors for preventing and treating obesity in children and their parents, especially those with excess body weight, may be of importance to prevent cardiovascular disease. Public policies, therefore, should aim at decreasing the parental obesity levels and birth weight, in addition to considering the entire family unit in the treatment of childhood obesity from birth.
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