Relative contribution of physical activity, sedentary

Relative contribution of physical activity, sedentary behaviors, and dietary habits to the prevalence of obesity among Kuwaiti adolescents

Ahmad R. Al-Haifi, Mohammad A. Al-Fayez, Buthaina I. Al-Athari, Fahhad A. Al-Ajmi, Ahmad R. Allafi, Hazzaa M. Al-Hazzaa, and Abdulrahman O. Musaiger Abstract Background. The increasing rate of obesity among Kuwaiti adolescents is associated with immediate and long term-risks to their health and well-being. Objective. To update data on the prevalence of overweight and obesity among Kuwaiti adolescents and to examine the relative contribution of selected lifestyle factors to overweight and obesity in this population. Methods. The present study is part of the Arab Teens Lifestyle Study (ATLS). A total of 906 adolescents (463 boys and 443 girls) aged between 14 and 19 years were selected from Kuwaiti schools by a multistage stratified randomization process. A validated questionnaire was used to collect data on physical activity, sedentary lifestyle, and eating habits. The International Obesity Task Force (IOTF) cutoff values for adolescents under 18 years of age were used to define overweight and obesity. Total energy expenditure was calculated using metabolic equivalent-minutes per week. A general linear model was used to establish the proportion of the variance (expressed in partial eta squared) in excess weight attributable to differences in eating habits and physical activity. Results. The prevalence of overweight and obesity was 50.5% in boys and 46.5% in girls. Among boys, moderate and vigorous activities were found to be

significantly negatively associated with overweight and obesity (p < .05), whereas in girls, only those with not less than moderate activities were negatively associated with overweight and obesity (p < .05). Sedentary behaviors, time spent watching television, and time spent working on the computer were not significantly associated with obesity in either sex. Consumption of breakfast, vegetables, and fast foods (boys and girls) and potatoes, cakes and doughnuts, and sweets (girls only) was significantly associated with overweight and obesity (p < .05). In general, the partial eta square explained by physical activity was less than 3.6% in boys compared with less than 1.0% in girls, and eating habits explained less than 1.8% in boys compared with 2.5% in girls. Conclusions. Physical activity explains a greater proportion of variation in body mass index than do eating habits, particularly in boys. Eating habits explain a greater proportion of variation in body mass index than does physical activity in girls. Prospective studies are needed to clarify the relative effects of sedentary behaviors on overweight in adolescents.

Key words: Adolescents, dietary habits, Kuwait, obesity, physical activity, sedentary behaviors

Introduction Ahmad R. Al-Haifi, Mohammed A. Al-Fayez, Buthaina I. Al-Athari, and Fahhad A. Al-Ajmi are affiliated with Food and Nutrition Science, College of Health Sciences, Kuwait; Ahmad R. Allafi is affiliated with the Department of Family Sciences, College for Women, Kuwait University; Hazzaa M. Al-Hazzaa is affiliated with the Pediatric Exercise Physiology Research Laboratory, College of Education, King Saud University, Riyadh, Saudi Arabia; Abdulrahman O. Musaiger is affiliated with the Nutrition and Health Studies Unit, Deanship of Scientific Research, University of Bahrain and Arab Center for Nutrition, Bahrain. Please direct queries to the corresponding author: Abdulrahman O. Musaiger, Nutrition and Health Studies Unit, Deanship of Scientific Research, University of Bahrain, Director, Arab Center for Nutrition, P. O. Box 26923; Manama, Bahrain; e-mail: [email protected].

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The increasing obesity problem in Kuwaiti society is a warning of impending health consequences. The prevalence of overweight and obesity among adults ranges between 70% and 80% [1–3]. However, the prevalence of overweight and obesity among Kuwaiti adolescents 10 to 19 years of age, which ranges from 42% to 45%, was reported to be among the highest prevalence rates worldwide, irrespective of the references used [4, 5]. Furthermore, obesity as a health problem is rising among this age group. In 2004, the overall rate of overweight and obesity among adolescent boys aged 10 to 14 years was 30.9% [6]. However, in 2009, the overall prevalence of overweight and obesity among

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Obesity among Kuwaiti adolescents

the same age group has reached 44.2% [7]. A similar trend is found among girls [7]. The yearly increase in the prevalence of overweight or obesity among Kuwaiti adolescents (from 2004 to 2009) is estimated to be 2.6% [7]. If childhood obesity is not taken seriously at an early stage, it can lead to lifelong obesity with associated health problems. Studies have estimated that 50% of children and 80% of adolescents with obesity will remain obese as adults [8, 9] and that the extra weight of body fat can lead to increased risks of heart disease, type 2 diabetes, some cancers, and psychological problems [10]. Although childhood obesity is increasing in all ethnic groups worldwide, its prevalence is higher in nonwhite populations [11]. The reasons for the differences in the prevalence of childhood obesity among different ethnic groups are complex. However, lifestyle variables play an important role in the development of childhood obesity [12]. Understanding the influence of lifestyle-related variables on overweight and obesity among Kuwaiti adolescents will be crucial for developing public policies and effective interventional strategies aimed at preventing and treating childhood obesity. The purpose of the present study was to update data on the prevalence of overweight and obesity among Kuwaiti adolescents and to examine the relative contribution of selected lifestyle factors to overweight and obesity in this population.

Methods The present study is part of the Arab Teens Lifestyle Study (ATLS). ATLS is a school-based, cross-sectional multicenter collaborative study [13]. The study protocol was approved by the Public Authority for Applied Education and Training as well as by the Ministry of Education and school principals in Kuwait. Informed consent was obtained from the parent of each participant. Data were collected by trained researchers with the supervision of the lead author. The participants filled in the ATLS questionnaire in their classrooms under the supervision of their teachers and in front of at least one of the research assistants. Participants

The target population of this study was adolescent boys and girls enrolled in Kuwaiti secondary schools during the school year 2009/10. A multistage, stratified, random sampling technique was used to select the sample. In the first stage, a systematic random sampling procedure was used to select the schools. The schools were stratified into boys’ and girls’ schools, with further stratification into public and private schools. The

selection of the private or public schools was proportional to size. At the second stage, classes were selected at each grade level using a simple random sampling design. In this way, one class was randomly selected in each of the three grades (grades 10, 11, and 12) in each secondary school. Data were collected in all six governances during the period from October through December 2009. Two schools from each governance were chosen (one for boys and one for girls), and then one class from each grade was randomly selected. A total of 36 classes plus 6 classes from a private school were selected, which included an average of 25 students in each class. All students in the selected classes who were free from any physical deformity were invited to participate in the study. The total number of selected students was 906 (463 boys and 443 girls). This represented 8% of the total number of secondary school students in Kuwait. All levels of education are free for Kuwaitis, and therefore the rate of dropping out of school is extremely low. Anthropometric measurements

Anthropometric variables included body weight, height, and waist circumference. All measurements were performed in the morning. Measurements were done with the subjects wearing minimal clothing and without shoes. Body weight was measured to the nearest 100 g with a calibrated portable scale (Detecto). Height was measured to the nearest centimeter with a calibrated measuring rod (Detecto) while the subject was in full standing position. Body mass index (BMI) was calculated as the weight in kilograms divided by the square of the height in meters. The International Obesity Task Force (IOTF) age- and sex-specific BMI cutoff reference standards [14] were used to identify overweight and obesity for adolescents between the ages of 14 and 17 years. For participants 18 years of age and above, the World Health Organization (WHO) cutpoints for adults [15] were used. Waist circumference was measured horizontally to the nearest 0.1 centimeter with a nonstretchable measuring tape at the level of the umbilicus. The participants were measured in private at an examination site in each school. When waist circumference was measured, the tape was snug but did not compress the skin. The waist/height ratio (WHtR) was calculated as the ratio of waist circumference to height in centimeters. Physical activity assessment

A self-reported questionnaire was used to assess the level of physical activity of the participants. The original questionnaire was previously shown to have a high reliability (intraclass correlation coefficient [ICC] = 0.85; 95% confidence limits [CL], 0.70 to 0.93)

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8

A. R. Al-Haifi et al.

[16] and acceptable validity (r = 0.37, p < .001) against physical activity level assessed by pedometer [13]. The questionnaire was designed to collect information on the frequency, duration, and intensity of a variety of light-, moderate-, and vigorous-intensity physical activities during a typical week. The physical activity questionnaire covered such domains as transport and household, fitness, and sports activities. Physical activities were assigned metabolic equivalent (MET) values based on the compendium of physical activity [17] and the compendium of physical activity for youth [18]. Moderate-intensity physical activity includes activities such as normal-pace walking, brisk walking, recreational swimming, household activities, and moderate-intensity recreational sports, such as volleyball, badminton, and table tennis. Household activities were given a mean MET value of 3. This was done because they included some items that may require fewer than 3 METs, such as washing dishes (2.5 METs), cleaning the bathroom (2.5 METs), cooking (2.5 METs), and ironing (2.3 METS), as well as other household activities that require 3 METs or more, such as car washing (3 METs), vacuuming (3.5 METs), mopping (3.5 METs), and gardening (3.5 METs). Moderate-intensity recreational sports were assigned a mean MET value of 4. Slow walking, normal-pace walking, and brisk walking were assigned MET values of 2.8, 3.5, and 4.5, respectively, based on modified MET values from the compendium of physical activity for youth [18]. Vigorous-intensity physical activities and sports included such activities as stair-climbing, jogging, running, cycling, self-defense, weight training, and vigorous sports, such as soccer, basketball, handball, and singles tennis. Vigorous-intensity sports were assigned an average MET value of 8. The percentage of adolescents who met daily physical activity recommendations [19] was calculated using cutoff scores equivalent to 1 hour per day of moderate-intensity (4 METs) physical activity. This amount of exercise was then converted into 1,680 MET-minutes per week (60 minutes per day × 7 days per week × 4 METs). Sedentary behaviors

The questions on sedentary behaviors came right after questions on physical activity. They asked for information about the amount of daily time spent in sedentary activities, including television viewing, playing video and computer games, and internet use. The participants were asked the average number of daily hours spent on these activities without differentiating between weekdays and weekends. For the total screen time cutoff points, we used the American Academy of Pediatrics guidelines of a maximum of 2 hours per day [20].

Eating habits

In addition to the physical activity questionnaire, the ATLS questionnaire included 10 specific questions in a separate section designed to determine the frequency of certain dietary habits of adolescents. The questions asked how many times per typical week the participants consumed breakfast; sugar-sweetened drinks, including soft beverages; vegetables (cooked and uncooked); fruit; potatoes; milk and dairy products; doughnuts or cakes; sweets (candy or chocolate); energy drinks; and fast foods. The fast foods included both western and Arabic choices, such as shawarma (grilled meat or chicken in pita bread with salad). These questions covered healthy and unhealthy dietary habits. For example, the consumption of fruit and vegetables, as well as regular intake of breakfast were considered healthy eating habits, whereas the high consumption of fast foods, sweetened beverages and energy drinks were considered unhealthy eating habits. Students had a choice of answers, ranging from zero intake to a maximum intake of 7 days per week. For the dietary cutoff points, we calculated the proportions of adolescents who had a daily intake of breakfast, fruits, vegetables, and milk and those who exceeded 3 days’ intake per week of the unhealthy foods. Statistical analysis

Data analysis was performed on a personal computer with the statistical software package SPSS, version 17.0. Descriptive statistics were performed on all the variables and were reported as mean values and standard deviations or percentages. In addition, a general linear model (GLM) was used to establish the variability in BMI and waist circumference that was attributable to physical activity, sedentary behaviors, and eating habits. The GLM was used to analyze the data, because this method allows regression analysis to be carried out in the presence of fixed factors such as categories of physical activity. It also allows physical activity, sedentary behaviors, and eating habits to be analyzed as continuous variables. Two commonly used measures of effect size in models involving fixed factors are eta squared and partial eta squared. Partial eta squared was used in the present study, which represents the variance due to the effect variable plus error [21, 22]; variance is excluded due to the independent effects of other variables. Partial eta squared gives the contribution of each variable or interaction as if it were the only variable, so that it is not masked by other variables. In the current study, partial eta squared was used as a measure of effect size (the proportion of the variance in BMI and waist circumference that is attributable to physical activity, sedentary behaviors, and eating habits). A p value less than .05 was considered to indicate statistical significance.


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Results The anthropometric characteristics of the participants are shown in table 1. There was no significant difference between boys and girls in mean age (p = .365), BMI (p < .113), or waist circumference (p < .074). There were significant differences between boys and girls in body weight (p < .001), height (p < .001), and WHtR (p < .001). The combined prevalence rates of overweight and obesity among the participants were 50.5% for boys and 46.5% for girls (p < .288).

The proportions of the variance in BMI and waist circumference that were explained by physical activity, sedentary behaviors, and eating habits are presented in table 2. In girls, only those with not less than moderate activities were associated with BMI (p < .05). With regard to sedentary behaviors, time spent watching television and time spent on the computer were not significantly related to BMI in boys or girls. Among boys, moderate activities were significantly related to waist circumference (but not to BMI) (p < .05), whereas activities in vigorous and those with not less than

TABLE 1. Anthropometric characteristics of the Kuwaiti adolescents (n = 906)a Characteristic

Total no.

Boys

Girls

p

906 905 905

16.3 ± 1.1 (463) 72.8 ± 21.0 (463) 169.3 ± 6.6 (463)

16.2 ± 1.2 (443) 62.6 ± 16.0 (442) 157.5 ± 6.0 (442)

.365 .001 .001 .288

228 212 440 905 899 899

25.0 (116) 25.5 (118) 50.5 (234) 463 83.1 ± 16.4 (462) 49.1 ± 9.3 (462)

25.5 (112) 21.0 (94) 46.5 (206) 442 84.9 ± 14.6 (437) 53.9 ± 9.0 (437)

Age (yr) Weight (kg) Height (cm) Weight Status (wt/ht2) Overweight Obese Overweight + obese Total no. Waist circumference (cm) Waist circumference/height

.074 .001

BMI, body mass index a. Values are means ± SD (no.).

TABLE 2. Proportion of variance of body mass index (BMI) and waist circumference (WC) explained by physical activity, sedentary behaviors, and eating habits for Kuwaiti adolescents (14 to 19 years)a Boys (n = 463) BMI Independent variable Moderate activitiesd Vigorous activitiese Not less than moderate activitiesf Television hours Computer hours Breakfast Sugar drinks Vegetables Fruits Milk Fast foods Potatoes Cakes and doughnuts Sweets Energy drinks

P

Girls (n = 443) WC

valueb

PESc

.092 .000 .000 .247 .784 .004 .921 .037 .427 .512 .024 .055 .053 .112 .608

.007 .035 .032 .003 .000 .018 .000 .009 .001 .001 .011 .008 .008 .006 .001

P

BMI

valueb

PESc

.043 .000 .000 .162 .831 .005 .718 .034 .628 .896 .013 .274 .103 .501 .926

.009 .036 .035 .004 .000 .017 .000 .010 .001 .000 .013 .003 .006 .001 .000

P

WC

valueb

PESc

.061 .121 .040 .231 .736 .001 .263 .075 .813 .191 .042 .001 .005 .012 .293

.009 .006 .010 .003 .000 .025 .003 .007 .000 .004 .010 .025 .018 .015 .003

P

valueb

PESc

.638 .864 .710 .577 .667 .029 .787 .410 .871 .129 .551 .020 .144 .136 .767

.001 .000 .000 .001 .000 .011 .000 .002 .000 .005 .001 .013 .005 .005 .000

a. P values and partial eta squared are shown for analysis using physical activity, sedentary behaviors, and eating habits as continuous variables, without any adjustments. b. P values < .05 are considered to indicate a statistically significant difference. c. PES: partial eta squared (proportions of variance). d. Moderate activities include activities such as walking at a normal pace, brisk walking, recreational swimming, badminton, and table tennis. e. Vigorous activities include activities such as jogging, running, self-defense, weight training, soccer, and basketball. f. Not less than moderate activities include both moderate and vigorous activities. Delivered by Publishing Technology to: Guest User IP: 77.69.242.150 on: Wed, 02 Apr 2014 03:18:07 Copyright (c) Nevin Scrimshaw International Nutrition Foundation. All rights reserved.

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Discussion

60

50

40

BMI

moderate categories were significantly associated with both BMI and waist circumference (p < .05) (fig. 1). In general, the partial eta square explained by physical activity and sedentary behaviors was less than 3.6% in boys compared with less than 1.0% in girls. With regard to eating habits, table 2 shows BMI and waist circumference were inversely related to breakfast intake in both boys and girls. Subjects who rarely ate breakfast were more likely to be overweight or obese. The intakes of vegetables (boys only), fast foods, potatoes, cakes and doughnuts, and sweets (girls only) were also significantly (p < .05) related to BMI, but not the other variables. However, only vegetables and fast foods (boys only) and potatoes (girls only) were significantly (p < .05) related to waist circumference. In general, the partial eta square explained by eating habits was less than 1.8% in boys compared with 2.5% in girls.

30

20 R2 linear = 0.029

10 0

10,000

20,000

30,000

40,000

Total “at least moderate physical activity level” (MET-min/wk)

FIG. 1. General linear regression model with dependent variable body mass index (BMI) based on parameter estimates for independent variable “at least moderate physical activity level” as measured by the continuous metabolic equivalents per minute per week (MET-min/ wk), among boys

The finding that Kuwaiti adolescents had a high prevalence of overweight or obesity is of great concern from a public health perspective. The prevalence of overweight or obesity is the highest reported among adolescents in the region. A recent study of Kuwaiti children reported a similar rate (46.6%) of overweight or obesity among 10-year-old boys [23]. In Dubai, the percentage of overweight or obese adolescents aged 12 to 17 years was reported to be 40.7% for boys and 33.6% for girls [24]. In Saudi Arabia, El Mouzan et al. [25] reported that the overall rates of overweight, obesity, and severe obesity among adolescents were 23.1%, 9.3%, and 2%, respectively. Obesity rates of 25.4% and 25.1% were reported for adolescents from Malta and the United States, respectively [26]. The rates of obesity among adolescents from Spain (19.5%), Canada (19%), England (18.2%), Italy (17.5), Greece (16.8%), France (11.5%), and Germany (11%) [26] are lower than those found in the present study of Kuwaiti adolescents. The present study reveals that being physically active (especially for boys) was associated with lower BMI and waist circumference, thus providing support for the role of physical activity in the maintenance of body weight and prevention of obesity. These findings are consistent with findings from other studies [26–32] showing that engaging in physical activity can assist in healthful weight-control behaviors. For example, Moliner-Urdiales et al. [28] examined the association of objectively assessed physical activity with markers of total and central body fat. They found that adolescents (n = 365) who engaged in at least a moderate level of physical activity for at least 60 minutes a day had lower

levels of total body fat (p < .05) and central body fat (p < .01). In addition, a significant negative relationship between physical activity (at least 60 minutes for 5 or more days a week) and overweight was noted in a larger survey of 34 countries involving 162,305 school-aged participants [26]. Therefore, it is important to note that adherence to current physical activity guidelines for weight loss is likely to be insufficient for the maintenance of a healthy body weight. Sedentary behaviors such as watching television and using the computer were not found to be associated with overweight and obesity among either boys or girls in the present study. This result is not consistent with other studies [33–36] which indicated that sedentary behavior is positively associated with overweight and obesity. The lack of association with sedentary behaviors found in this study suggests the need for further investigation of these behaviors. A number of eating habits were found to be associated with overweight and obesity among the Kuwaiti adolescents. Avoidance of breakfast was significantly positively related to BMI and waist circumference. This finding is in agreement with several studies clearly indicating that skipping breakfast is the most important risk factor for overweight and obesity [37–40]. This finding may be useful in targeting prevention and intervention programs and strategies for childhood and adolescent obesity in schools. As expected, a significant increase in the risk of being overweight and obese was found with increased frequency of eating potatoes or sweets among girls, but not among boys. These findings are consisted with


11


those of Chacar and Salameh [41]. In contrast, eating vegetables was associated with a lower risk of being overweight and obese only in boys. Such findings were also reported by bin Zaal et al. [24] among adolescents in the United Arab Emirates. However, one confusing finding of the study is that fruit intake was not associated with overweight and obesity in either sex. Fast food consumption was found to be significantly associated with overweight and obesity in many studies [24, 42, 43] that reveal detectable effects in a vulnerable group of children and adolescents. Accessibility of various types of food venues is associated with BMI percentile in eastern North Carolina youth [44]. In the present study, high consumption of fast foods was found to be associated with increased risks of high BMI and waist circumference in boys and of high BMI in girls. Although sugar-sweetened beverages are widely believed to be contributing to the growing prevalence of overweight and obesity around the world [45, 46], a relationship of sugar drinks, fruits, milk, and energy drinks with overweight and obesity was not clearly determined in this study. These findings are in agreement with those of O’Connor et al. [47], who found that weight status had no association with the amount of total beverages, milk, 100% fruit juice, fruit drink, or soda consumed. However, in a comparable study, countries with high obesity prevalence, such as the United States, England, Spain, and Canada, show a trend, with 48.2%, 38.1%, 29.8%, and 21.1%, respectively, of overweight adolescents having higher levels of intake of soft drinks [26]. Because the study used self-report measures for physical activity and eating habits, errors in measurements may have occurred. The main limitation of this study is that it was not designed to estimate portion sizes and differences between socioeconomic groups, which may limit the generalizability of the results. However, like some questionnaires validated in other countries, this approach keeps the questionnaire

relatively brief and easy for adolescents to complete with minimal assistance [48, 49]. Despite these limitations, the results of this study are strengthened by a reasonable sample size and the use of a well-validated instrument to elicit information. This study provides the public health and education authorities in Kuwait with evidence of the beneficial effects of physical activity and healthy eating habits on overweight and obesity, which are now well established. Proper interventions are needed to accommodate physical activities in health care and educational programs in Kuwait. A regular pattern of physical exercise must be included within the routine life, and institutional curricula need to be modified by including more time for physical drills. In addition, the findings indicated that there is a strong relationship between unhealthy food habits and obesity. In this regard, a role for school and family is proposed with the aim of orienting young people toward intrinsic goals in an attempt to enhance future eating habits, exercise behavior, and quality of life. Improving the nutritional quality of foods offered from other sources, such as the National School Lunch Program and competitive foods, could help improve adolescent dietary behaviors [50].

Acknowledgments We would like to give special thanks to the Ministry of Education and all the schools and adolescents who participated in this study. We would like to thank the Public Authority for Applied Education and Training (PAAET) for financial support of this study. We would also like to extend our gratitude to all students of the College of Health Sciences who helped in collecting the data. The authors declare that they have no competing interests and financial disclosures associated with this study.

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