This article was downloaded by: [Central Michigan University] On: 29 December 2014, At: 11:38 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Behavioral Medicine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vbmd20
Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents a
HakGweon Lee & YoungHo Kim
a
a
Seoul National University of Science and Technology Accepted author version posted online: 25 Apr 2014.Published online: 10 Oct 2014.
Click for updates To cite this article: HakGweon Lee & YoungHo Kim (2014): Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents, Behavioral Medicine, DOI: 10.1080/08964289.2014.914463 To link to this article: http://dx.doi.org/10.1080/08964289.2014.914463
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
BEHAVIORAL MEDICINE, 0: 1–8, 2014 Copyright Ó Taylor & Francis Group, LLC ISSN: 0896-4289 print / 1940-4026 online DOI: 10.1080/08964289.2014.914463
Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents Downloaded by [Central Michigan University] at 11:38 29 December 2014
HakGweon Lee and YoungHo Kim Seoul National University of Science and Technology
The current study investigated the effect of an obesity intervention incorporating physical activity and behavior-based motivational enhancement intervention on BMI, physical activity levels, and psychological variables toward physical activity in male obese adolescents. Single group study without having a control group was carried out in Korea. Sixty-eight obese male adolescents who had BMI greater than 25 kg/m2 participated in the 16-week obesity intervention. During this period, the study participants’ BMI, physical activity levels, self-efficacy, and perceived benefits and barriers were measured at the three time point (baseline, after week 8, and after week 16). Results indicated that obese adolescents’ BMI significantly decreased (F D 3.51, p D .03) and physical activity (F D 4.01, p D .02) significantly increased over the 16-week obesity intervention. In addition, Exercise self-efficacy (F D 5.02) and perceived benefits toward physical activity (F D 5.34) significantly increased but perceived barriers of physical activity (F D 5.10) gradually decreased over the intervention. This study suggests that an obesity intervention combining physical activity and behavior-based motivational enhancement intervention significantly contributed to decreased BMI, increased physical activity, and positively changed psychological variables related to physical activity. This first application has resulted in preliminary support for this intervention modality within non-western obese adolescents.
Keywords: obese adolescent, perceived benefits, perceived barriers, physical activity, selfefficacy
Obesity is becoming increasingly prevalent throughout the world, making it an ever more serious public health issue. Particularly, the obesity rates in adolescents have grown more rapidly compared with other age groups. According to one large US study, the obesity incidence in elementary school students increased more than two-fold, from 6.5% in 1980 to 17% in 2006.1 In adolescents, this increase was even greater—more than three-fold—around the same period of time, from 5% to 17%.1 Likewise, in Korea, the number of obese adolescents has increased consistently in recent years. According to the Ministry of Health and Welfare, the adolescent obesity incidence accounts for 10.2% Correspondence should be addressed to YoungHo Kim, Department of Sport Science, Seoul National University of Science and Technology, 172 Gongneung dong, Nowon gu, 139-743, Seoul, Korea. E-mail: [email protected]
of the total obesity incidence; in addition, 22.9% of male adolescents are obese, which is considerably higher than the 13.4% of female counterparts. These figures represent a 1.3-fold increase for boys and a 1.6-fold increase for girls compared with the data from 1998.2 Numerous studies have pointed out significant relationships between obesity and various health problems such as cardiovascular diseases, type-2 diabetes, hypertension, and certain types of cancer.3,4 Particularly, obesity in adolescents damages self-esteem and can lead to severe states of psychological insecurity. In addition, obesity during this life stage has a very high probability of continuing into adulthood.5 Many people believe that the main reasons for adolescent obesity are a high-fat diet and excessive caloric intake, and recognize that changing eating habits is an important prevention method. However, researchers have recently
Downloaded by [Central Michigan University] at 11:38 29 December 2014
2
LEE AND KIM
reported that, although the average individual energy intake is constantly decreasing, the obesity rate is continuing to increase across the world5. One explanation for this would be lack of sufficient physical activity.6 Additionally, according to another study, about 25% of the population was considered obese between 1986 and 1990, and this figure has reached upwards of 33.4% at present, even though the average energy intake and fat consumption has decreased since then.7 Accordingly, the researchers maintained that decrease in physical activity was the main reason for the increased obesity rate, rather than undesirable eating habits.6,7 Thus, current literature suggests that the total obesity rate may be increasing because the decrease in physical activity is occurring faster than the decrease in energy intake. A large number of studies have reported that adolescents are gradually engaging in less physical activity, which is indirect evidence of a relationship between lack of physical activity and adolescent obesity.8,9 In support of this, several studies have pointed out that participation in physical activity is noticeably lower in obese adolescents compared with normal-weight counterparts.10,11 Deforche and colleagues investigated physical activity of normal-weight and obese adolescents and found no significant difference between the two groups in terms of moderate physical activity; however, normal-weight adolescents engaged in significantly more strenuous physical activity than obese peers.12 Recently, Kim, Kim, Cha, and Kang found significant differences in physical activity among adolescents with different BMI. Particularly, obese adolescents participated less in physical activity of all intensity levels (eg, mild, moderate, and strenuous), compared with normal-weight counterparts.13 It has been broadly recognized that motivating obese adolescents to adhere to physical activity is very important and it is significant to identify the specific reasons obese adolescents are less physically active. A large number of studies indicated that various psychological variables such as self-efficacy, perception, and attitudes are significantly associated with lack of physical activity in obese adolescents.14,15 These cross-sectional findings can serve as valuable data for the promotion of physical activity among the obese population. Given the significant between psychological variables and physical activity in obese adolescents, longitudinal intervention studies aimed at increasing physical activity and its related psychological attributes are needed in this age group. Several studies have found that an obesity intervention has significant effects to increase physical activity levels and the related psychological variables.16,17 Specifically, Logue and colleagues studied the effect of a 6-week obesity treatment on weight loss and changes in physical activity in obese adolescents. In this study, most of the obese adolescents showed significant weight loss and considerable increases in physical activity levels after the treatment.18 In addition, Seals applied a psychological reinforcement
program to identify changes in the psychological attributes related to physical activity in obese adolescents.18 In this study, obese students were offered an 8-week jump rope exercise program, after which they exhibited significant decreases in BMI and increases in exercise self-efficacy and perceived benefits of physical activity.19 Despite the significant effects of interventions in increasing physical activity and improving its related psychological attributes in obese adolescents, as indicated above, these studies have been primarily undertaken in western countries; such research is lacking in other cultures, such as Korea, where intervention studies focused on physical activity and psychological variables among obese adolescents has only recently gained attention. Therefore, the current study investigated the effect of an obesity intervention incorporating physical activity and behavior-based motivational enhancement intervention on BMI, physical activity levels, and psychological variables toward physical activity in male obese adolescents.
METHODS Participants Because this study addressed weight-related variables which are a sensitive issue for adolescents, we thought it inappropriate to conduct the study on both male and female adolescents. Accordingly, as female students in puberty are more likely to be very sensitive about weight and body shape and the latest data in Korea suggest that the obesity rate is increasing faster in male adolescents compared with female peers,2,13 we selected only male adolescents as participants for this study. At the initial stage, we selected a preliminary sample of participants, which included the male students from S junior high school located in K district of Seoul who had BMI greater than 25 kg/m2 (n D 210). This BMI was based on the records of a school health check-up carried out a year prior to the intervention. Then, the preliminary participants’ (n D 210) BMI was re-measured and those who still had BMI greater than 25 kg/m2 were selected as eligible participants (n D 125). The purpose and procedures of the study were explained to these students and their parents, and consent forms requesting their voluntary participation were distributed. A total of 68 students and their parents consented to participate in the 16-week obesity intervention. During this period, the study participants’ BMI, physical activity levels, selfefficacy, and perceived benefits and barriers were measured at the three time points. The first measurement was taken for all 68 participants at baseline, the second measurement was taken at the 8-week intervention for those who remained in the program (n D 64, 94.1%), and the final measurement was taken for 61 participants (89.7%) who completed the 16-week intervention. During the
OBESITY INTERVENTION WITH MALE OBESE ADOLESCENTS
intervention no one was injured and adverse events were not happened. This study was approved by the Institutional Review Board of Seoul National University of Science and Technology. Table 1 illustrates the general characteristics of study participants.
Downloaded by [Central Michigan University] at 11:38 29 December 2014
Measures The questionnaires applied in the current study were originally developed in English and translated into Korean using the methodology outlined by Banville, Desrosiers, and Genet-Volet.20 The full translation and validation processes have been described elsewhere.21,22 The study participants’ BMI (kg/m2) was measured by using an InBody Body Composition Analyzer (Model J10, Biospace Co., Korea). This analyzer measured participants’ current body composition by using bioelectrical impedance analysis, and evaluates the balance between muscle and body fat. To calculate the BMI scores, participants’ height and weight were directly measured and transformed to metric equivalents (ie, kilograms and meters) in the analyzer. The exercise self-efficacy scale developed by Bandura was translated into Korean, and used in this study to measure the self-confidence of the participants with regard to undertaking physical activity.23 The revised scale consisted of 18 items, with a 5-point response format ranging from 1 (not at all confident) to 5 (extremely confident). Individuals rated the degree of confidence they possessed that they could exercise regularly (ie, at least five times per week) under various circumstances (eg, When I am sick or on a vacation). A two-week, test–retest reliability was performed, resulting in a intraclass correlation coefficient of .91.21 In addition, Construct validity was examined based on the results of a factor analysis and supported in the current study. The decisional balance scale for exercise developed by Plotnikoff, Blanchard, Hotz, and Rhodes was adapted for Korea, and applied to assess the perceived benefits and barriers of exercise.24 This 5-point scale consisted of 10 items (ie, five benefits and five barriers), and participants were asked to indicate how important each statement was to them with regard to their decision of whether or not to exercise. Response ranged between 1 (strongly disagree) and 5 (strongly agree). An example of perceived benefit item is “regular physical activity would help me have a more TABLE 1 Study Participants’ Characteristics
Age (yr) Height (cm) Weight (kg) BMI (kg/m2)
Baseline (n D 68)
8 weeks (n D 64)
16 weeks (n D 61)
15.37 § 0.77 170.02 § 5.47 76.79 § 10.01 28.32 § 1.99
15.23 § 0.61 170.97 § 6.00 75.04 § 10.77 28.12 § 2.20
15.16 § 0.72 172.08 § 6.58 74.33 § 10.31 26.42 § 2.57
3
positive outlook” and an example of perceived barrier item is “I would feel embarassed if people saw me exercising.” A two-week test–retest reliability was performed, resulting in a intraclass correlation coefficient of .81 for perceived benefits and .78 for perceived barriers.21 In addition, based on a factor analysis, construct validity of this measure was supported. A leisure-time physical-activity scale developed by Godin and Shephard was adapted for Korea and used in the present study to assess habitual weekly physical activity behaviors.25 Participants reported how many times during a typical week they took part in strenuous (eg, running, vigorous cycling), moderate (eg, fast walking, easy swim), and mild (eg, yoga, golf) physical activity for more than 15 minutes. Scores were calculated by multiplying each reported activity session by its metabolic equivalent (MET) value and adding the result; MET score D (strenuous £ 9) C (moderate £ 5) C (mild £ 3). The two-week, test–retest intraclass correlation coefficient for the Korean version of the LTEQ was .86.26 Construct validity of the Korean LTEQ was supported by correlation with an accelerometer in the previous study (Spearman’s rho D .77).27 Procedures Prior to initiating the intervention on the first day of the obesity program, the general characteristics (ie, age, height, body weight, BMI), psychological variables (self-efficacy, perceived benefits, perceived barriers), and physical activity of the study participants were measured. After completing baseline measurement, participants took part in the obesity intervention, which lasted for 16 weeks (5 days a week and a total of 80 sessions). The intervention was conducted in the gym and classroom of S middle school from 8:00 am to 8:50 a.m. After 8 and 16 weeks of the intervention, we assessed the same variables as at baseline. To increase retention, for every weekend during the intervention a text message explaining the goals and content of the intervention for the following week was sent to participants and their parents. The participants received a $50 exercise voucher three times during the intervention. The voucher could be exchanged with various sport goods such as socks, t-shirt, and soccer ball. Obesity Intervention The obesity intervention consisted of physical activity and behavior-based motivational enhancement intervention associated with physical activity. The physical activity in this study consisted of various jump rope exercises, which participants engaged in 3 times a week for 50 minutes (consisting of warm-up for 5 minutes, jump rope for 40 minutes, and cool-down for 5 minutes). The warm-up session aimed to increase participants’ interest in exercise and improve their joint mobility, and included jogging and flexibility
4
LEE AND KIM TABLE 2 Obesity Intervention Obesity Intervention Psychological strategy (2 times/week)
Week
4–5
Explanation of the effect of jump rope Explanation and demonstration of how to implement jump rope Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope)
6–8
Intensity: 55–60% of HR max
9–10
Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope) Intensity: 60–65% of HR max
1–2
3
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Physical activity (3 times/week) Jump rope
11–12
13 14
15 16
Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope)
Intensity: 65–70% of HR max
Topic
Strategy
Understanding of obesity Goal setting
Introduction of psychological strategy Awareness of obesity-related problems Setting the target weight
Identification of current level
Physical activity test (METs score) Self-efficacy test Perceived benefits and barriers test Finding one’s reasons for not doing physical activity Discussing one’s lifestyle Setting an achievable physical activity plan Understanding the importance and effect of physical activity Finding calorie consumption by an activity type Discussing one’s physical activity habits Understanding the meaning and scope of self-efficacy Identifying the relationship between self-efficacy and physical activity Enhancing confidence for promoting physical activity Understanding the importance of motivation and perception toward physical activity Recognizing the benefits and barriers of physical activity Exploring the way to enhance motivation and perceived benefits Understanding the meaning and resources of social support Asking support from friends and families Sharing one’s thought and experiences about obesity and physical activity with others Replacing negative factors for physical activity and weight control with positive ones Setting new physical activity goal for maintaining proper weight Summarizing obesity intervention Identifying the attainment of one’s goal and rewarding for it
Identification of one’s problems Setting of new plan for behavioral change Physical activity Self-efficacy
Motivation Perceived benefits and barriers
Social support Awareness change
Setting new goal for weight control Conclusion of intervention
exercises. The cool-down session was to help return the heart rate to its normal level, and included muscle flexibility and stretching. The intensity of the jump rope exercise started at 55%–60% of maximum heart rate and gradually increased to 60%–70% of maximum heart rate. In order to promote participants’ motivation, various jump rope exercises were implemented with music. These exercises included single jump rope, partner jump rope, double unders jump rope, and group jump rope using a long rope.28 The behavior-based motivational enhancement intervention applied in this study was based on materials used in previous studies.28,29 The intervention was designed to help obese adolescents regularly participate in physical activity by employing current scientific understanding of the various psychological variables that influence weight control and corresponding strategies to modify such variables (eg, if an obese adolescent is unable to participate in physical activity on a regular basis, a psychological technique would
include offering motivational content such as accurate information about the advantages of regular physical activity). In specific, at the beginning of the intervention, awareness of perceived benefits and barriers was emphasized to raise participants’ awareness of the severity of obesity-related health problems and the benefits of physical activity. Midway through the intervention, practical techniques for enhancing self-efficacy and social support (ie, setting an achievable physical activity plan and enhancing confidence for promoting physical activity) were emphasized to help participants realize the importance of building confidence and social support to encourage regular physical activity. The final stage of the intervention emphasized motivation-based psychological reinforcement techniques (ie, setting new physical activity goal for maintaining proper weight and identifying the attainment of one’s goal and rewarding for physical activity) for each participant to continue to lose weight and to maintain regular physical activity.
OBESITY INTERVENTION WITH MALE OBESE ADOLESCENTS
Data Analysis Descriptive statistics (ie, mean and standard deviation) were conducted to summarize the participants’ characteristics. In addition, a repeated measures ANOVA was carried out to examine the change in BMI, the levels of physical activity, and psychological variables (self-efficacy, perceived benefits, and perceived barriers) over 16 weeks (p < .05). Post hoc Bonferroni-corrected tests were used to identify significant differences between each of the three time points. All statistical analyses were conducted using SPSS 18.0.
Downloaded by [Central Michigan University] at 11:38 29 December 2014
RESULTS Effects of the Obesity Intervention on BMI and Physical Activity A repeated-measures ANOVA was carried out to examine how BMI and physical activity among participants changed over the 16-week obesity intervention and the results are shown in Table 3. Obese adolescents’ BMI consistently decreased over the 16 weeks and this was statistically significant (F D 3.51, p D .03). Moreover, across the 16 weeks, obese adolescents’ total amount of physical activity steadily increased and these changes were statistically significant (F D 4.01, p D .02). Interestingly, we found that the amount of mild physical activity (F D 7.24, p < .001) and moderate physical activity (F D 8.99, p < .001) showed significant increases across all three time points, but there was no significant change in the amount of strenuous physical activity (F D 1.31, p D 0.31). Effects of the obesity intervention on psychological variables related to physical activity Table 4 illustrates the results of the repeated measures ANOVA on whether the psychological strategy of the obesity intervention effectively improved psychological variables relating to physical activity. Results indicated that psychological variables were significantly changed over the 16-week intervention. In specific, obese adolescents’ self-efficacy (F D 5.02, p D .01) and perceived benefits (F D 5.34, p D .02) significantly increased and their perceived barriers (F D 5.10, p D .02)
5
significantly decreased over the 16 weeks. In specific, obese adolescents showed significant increases in ‘weight control (F D 8.67, p < .001) and ‘better outlook’ (F D 3.67, p D .04) in perceived benefits. In perceived barriers toward physical activity, ‘physical satisfaction’ (F D 11.23, p < .001), ‘lack of competence’ (F D 4.01, p D .03), and ‘tiredness’ (F D 3.96, p D .03) were significantly reduced.
DISCUSSION Although there is a wide body of research indicating that obesity has a negative influence on health, the obesity rate is rapidly increasing across all age groups and the rise in adolescence is particularly alarming. In behavioral medicine, it has been widely supported that adolescents’ obesity is significantly associated with physical inactivity and its related psychological variables. With this background, the focus of the present study was to investigate whether an obesity intervention combining physical activity and psychological strategy can decrease BMI, improve physical activity and positively change psychological variables relating to physical activity among obese adolescents. Results indicated that obese adolescents’ BMI continuously decreased over the 16 weeks of jump rope exercises. This finding is supported by previous studies demonstrating that regular physical activity helps decrease body fat and promote weight regulation.17,30,31 In particular, because medications for obesity control have been shown to have little effect and many side effects, and as dietary regulation is not recommended to adolescents who are still growing, participation in regular physical activity is being regarded as the most effective way to reduce weight for obese adolescents.32 In addition, obese adolescents’ physical activity significantly increased across the obesity intervention. Interestingly, there was significant change in the levels of mild and moderate physical activity, but strenuous physical activity did not substantially change over the intervention. These findings can be understood by several reasons. First, on a basis of an assumption that participating in jump rope 5 days a week for the 16 weeks might not be an easy task for obese adolescents due to limitations of physical fitness,
TABLE 3 Changes in BMI and Physical Activity by the obesity Intervention
2
BMI (kg/m ) Total PA(METs) Mild PA Moderate PA Strenuous PA
Baseline1 (M § SD)
8weeks2 (M § SD)
16 weeks3 (M § SD)
Ftime
p
28.32 § 1.99 57.42 § 11.05 12.71 § 11.23 17.38 § 10.95 27.33 § 11.04
28.12 § 2.20 70.78 § 15.69 17.63 § 13.33 24.14 § 15.21 29.01 § 16.04
26.42 § 2.57 83.12 § 11.04 22.53 § 10.86 29.37 § 10.61 31.22 § 10.49
3.51 4.01 7.24 8.99 1.31
.03 .02
Behavioral Medicine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vbmd20
Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents a
HakGweon Lee & YoungHo Kim
a
a
Seoul National University of Science and Technology Accepted author version posted online: 25 Apr 2014.Published online: 10 Oct 2014.
Click for updates To cite this article: HakGweon Lee & YoungHo Kim (2014): Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents, Behavioral Medicine, DOI: 10.1080/08964289.2014.914463 To link to this article: http://dx.doi.org/10.1080/08964289.2014.914463
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
BEHAVIORAL MEDICINE, 0: 1–8, 2014 Copyright Ó Taylor & Francis Group, LLC ISSN: 0896-4289 print / 1940-4026 online DOI: 10.1080/08964289.2014.914463
Effects of an Obesity Intervention Integrating Physical Activity and Psychological Strategy on BMI, Physical Activity, and Psychological Variables in Male Obese Adolescents Downloaded by [Central Michigan University] at 11:38 29 December 2014
HakGweon Lee and YoungHo Kim Seoul National University of Science and Technology
The current study investigated the effect of an obesity intervention incorporating physical activity and behavior-based motivational enhancement intervention on BMI, physical activity levels, and psychological variables toward physical activity in male obese adolescents. Single group study without having a control group was carried out in Korea. Sixty-eight obese male adolescents who had BMI greater than 25 kg/m2 participated in the 16-week obesity intervention. During this period, the study participants’ BMI, physical activity levels, self-efficacy, and perceived benefits and barriers were measured at the three time point (baseline, after week 8, and after week 16). Results indicated that obese adolescents’ BMI significantly decreased (F D 3.51, p D .03) and physical activity (F D 4.01, p D .02) significantly increased over the 16-week obesity intervention. In addition, Exercise self-efficacy (F D 5.02) and perceived benefits toward physical activity (F D 5.34) significantly increased but perceived barriers of physical activity (F D 5.10) gradually decreased over the intervention. This study suggests that an obesity intervention combining physical activity and behavior-based motivational enhancement intervention significantly contributed to decreased BMI, increased physical activity, and positively changed psychological variables related to physical activity. This first application has resulted in preliminary support for this intervention modality within non-western obese adolescents.
Keywords: obese adolescent, perceived benefits, perceived barriers, physical activity, selfefficacy
Obesity is becoming increasingly prevalent throughout the world, making it an ever more serious public health issue. Particularly, the obesity rates in adolescents have grown more rapidly compared with other age groups. According to one large US study, the obesity incidence in elementary school students increased more than two-fold, from 6.5% in 1980 to 17% in 2006.1 In adolescents, this increase was even greater—more than three-fold—around the same period of time, from 5% to 17%.1 Likewise, in Korea, the number of obese adolescents has increased consistently in recent years. According to the Ministry of Health and Welfare, the adolescent obesity incidence accounts for 10.2% Correspondence should be addressed to YoungHo Kim, Department of Sport Science, Seoul National University of Science and Technology, 172 Gongneung dong, Nowon gu, 139-743, Seoul, Korea. E-mail: [email protected]
of the total obesity incidence; in addition, 22.9% of male adolescents are obese, which is considerably higher than the 13.4% of female counterparts. These figures represent a 1.3-fold increase for boys and a 1.6-fold increase for girls compared with the data from 1998.2 Numerous studies have pointed out significant relationships between obesity and various health problems such as cardiovascular diseases, type-2 diabetes, hypertension, and certain types of cancer.3,4 Particularly, obesity in adolescents damages self-esteem and can lead to severe states of psychological insecurity. In addition, obesity during this life stage has a very high probability of continuing into adulthood.5 Many people believe that the main reasons for adolescent obesity are a high-fat diet and excessive caloric intake, and recognize that changing eating habits is an important prevention method. However, researchers have recently
Downloaded by [Central Michigan University] at 11:38 29 December 2014
2
LEE AND KIM
reported that, although the average individual energy intake is constantly decreasing, the obesity rate is continuing to increase across the world5. One explanation for this would be lack of sufficient physical activity.6 Additionally, according to another study, about 25% of the population was considered obese between 1986 and 1990, and this figure has reached upwards of 33.4% at present, even though the average energy intake and fat consumption has decreased since then.7 Accordingly, the researchers maintained that decrease in physical activity was the main reason for the increased obesity rate, rather than undesirable eating habits.6,7 Thus, current literature suggests that the total obesity rate may be increasing because the decrease in physical activity is occurring faster than the decrease in energy intake. A large number of studies have reported that adolescents are gradually engaging in less physical activity, which is indirect evidence of a relationship between lack of physical activity and adolescent obesity.8,9 In support of this, several studies have pointed out that participation in physical activity is noticeably lower in obese adolescents compared with normal-weight counterparts.10,11 Deforche and colleagues investigated physical activity of normal-weight and obese adolescents and found no significant difference between the two groups in terms of moderate physical activity; however, normal-weight adolescents engaged in significantly more strenuous physical activity than obese peers.12 Recently, Kim, Kim, Cha, and Kang found significant differences in physical activity among adolescents with different BMI. Particularly, obese adolescents participated less in physical activity of all intensity levels (eg, mild, moderate, and strenuous), compared with normal-weight counterparts.13 It has been broadly recognized that motivating obese adolescents to adhere to physical activity is very important and it is significant to identify the specific reasons obese adolescents are less physically active. A large number of studies indicated that various psychological variables such as self-efficacy, perception, and attitudes are significantly associated with lack of physical activity in obese adolescents.14,15 These cross-sectional findings can serve as valuable data for the promotion of physical activity among the obese population. Given the significant between psychological variables and physical activity in obese adolescents, longitudinal intervention studies aimed at increasing physical activity and its related psychological attributes are needed in this age group. Several studies have found that an obesity intervention has significant effects to increase physical activity levels and the related psychological variables.16,17 Specifically, Logue and colleagues studied the effect of a 6-week obesity treatment on weight loss and changes in physical activity in obese adolescents. In this study, most of the obese adolescents showed significant weight loss and considerable increases in physical activity levels after the treatment.18 In addition, Seals applied a psychological reinforcement
program to identify changes in the psychological attributes related to physical activity in obese adolescents.18 In this study, obese students were offered an 8-week jump rope exercise program, after which they exhibited significant decreases in BMI and increases in exercise self-efficacy and perceived benefits of physical activity.19 Despite the significant effects of interventions in increasing physical activity and improving its related psychological attributes in obese adolescents, as indicated above, these studies have been primarily undertaken in western countries; such research is lacking in other cultures, such as Korea, where intervention studies focused on physical activity and psychological variables among obese adolescents has only recently gained attention. Therefore, the current study investigated the effect of an obesity intervention incorporating physical activity and behavior-based motivational enhancement intervention on BMI, physical activity levels, and psychological variables toward physical activity in male obese adolescents.
METHODS Participants Because this study addressed weight-related variables which are a sensitive issue for adolescents, we thought it inappropriate to conduct the study on both male and female adolescents. Accordingly, as female students in puberty are more likely to be very sensitive about weight and body shape and the latest data in Korea suggest that the obesity rate is increasing faster in male adolescents compared with female peers,2,13 we selected only male adolescents as participants for this study. At the initial stage, we selected a preliminary sample of participants, which included the male students from S junior high school located in K district of Seoul who had BMI greater than 25 kg/m2 (n D 210). This BMI was based on the records of a school health check-up carried out a year prior to the intervention. Then, the preliminary participants’ (n D 210) BMI was re-measured and those who still had BMI greater than 25 kg/m2 were selected as eligible participants (n D 125). The purpose and procedures of the study were explained to these students and their parents, and consent forms requesting their voluntary participation were distributed. A total of 68 students and their parents consented to participate in the 16-week obesity intervention. During this period, the study participants’ BMI, physical activity levels, selfefficacy, and perceived benefits and barriers were measured at the three time points. The first measurement was taken for all 68 participants at baseline, the second measurement was taken at the 8-week intervention for those who remained in the program (n D 64, 94.1%), and the final measurement was taken for 61 participants (89.7%) who completed the 16-week intervention. During the
OBESITY INTERVENTION WITH MALE OBESE ADOLESCENTS
intervention no one was injured and adverse events were not happened. This study was approved by the Institutional Review Board of Seoul National University of Science and Technology. Table 1 illustrates the general characteristics of study participants.
Downloaded by [Central Michigan University] at 11:38 29 December 2014
Measures The questionnaires applied in the current study were originally developed in English and translated into Korean using the methodology outlined by Banville, Desrosiers, and Genet-Volet.20 The full translation and validation processes have been described elsewhere.21,22 The study participants’ BMI (kg/m2) was measured by using an InBody Body Composition Analyzer (Model J10, Biospace Co., Korea). This analyzer measured participants’ current body composition by using bioelectrical impedance analysis, and evaluates the balance between muscle and body fat. To calculate the BMI scores, participants’ height and weight were directly measured and transformed to metric equivalents (ie, kilograms and meters) in the analyzer. The exercise self-efficacy scale developed by Bandura was translated into Korean, and used in this study to measure the self-confidence of the participants with regard to undertaking physical activity.23 The revised scale consisted of 18 items, with a 5-point response format ranging from 1 (not at all confident) to 5 (extremely confident). Individuals rated the degree of confidence they possessed that they could exercise regularly (ie, at least five times per week) under various circumstances (eg, When I am sick or on a vacation). A two-week, test–retest reliability was performed, resulting in a intraclass correlation coefficient of .91.21 In addition, Construct validity was examined based on the results of a factor analysis and supported in the current study. The decisional balance scale for exercise developed by Plotnikoff, Blanchard, Hotz, and Rhodes was adapted for Korea, and applied to assess the perceived benefits and barriers of exercise.24 This 5-point scale consisted of 10 items (ie, five benefits and five barriers), and participants were asked to indicate how important each statement was to them with regard to their decision of whether or not to exercise. Response ranged between 1 (strongly disagree) and 5 (strongly agree). An example of perceived benefit item is “regular physical activity would help me have a more TABLE 1 Study Participants’ Characteristics
Age (yr) Height (cm) Weight (kg) BMI (kg/m2)
Baseline (n D 68)
8 weeks (n D 64)
16 weeks (n D 61)
15.37 § 0.77 170.02 § 5.47 76.79 § 10.01 28.32 § 1.99
15.23 § 0.61 170.97 § 6.00 75.04 § 10.77 28.12 § 2.20
15.16 § 0.72 172.08 § 6.58 74.33 § 10.31 26.42 § 2.57
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positive outlook” and an example of perceived barrier item is “I would feel embarassed if people saw me exercising.” A two-week test–retest reliability was performed, resulting in a intraclass correlation coefficient of .81 for perceived benefits and .78 for perceived barriers.21 In addition, based on a factor analysis, construct validity of this measure was supported. A leisure-time physical-activity scale developed by Godin and Shephard was adapted for Korea and used in the present study to assess habitual weekly physical activity behaviors.25 Participants reported how many times during a typical week they took part in strenuous (eg, running, vigorous cycling), moderate (eg, fast walking, easy swim), and mild (eg, yoga, golf) physical activity for more than 15 minutes. Scores were calculated by multiplying each reported activity session by its metabolic equivalent (MET) value and adding the result; MET score D (strenuous £ 9) C (moderate £ 5) C (mild £ 3). The two-week, test–retest intraclass correlation coefficient for the Korean version of the LTEQ was .86.26 Construct validity of the Korean LTEQ was supported by correlation with an accelerometer in the previous study (Spearman’s rho D .77).27 Procedures Prior to initiating the intervention on the first day of the obesity program, the general characteristics (ie, age, height, body weight, BMI), psychological variables (self-efficacy, perceived benefits, perceived barriers), and physical activity of the study participants were measured. After completing baseline measurement, participants took part in the obesity intervention, which lasted for 16 weeks (5 days a week and a total of 80 sessions). The intervention was conducted in the gym and classroom of S middle school from 8:00 am to 8:50 a.m. After 8 and 16 weeks of the intervention, we assessed the same variables as at baseline. To increase retention, for every weekend during the intervention a text message explaining the goals and content of the intervention for the following week was sent to participants and their parents. The participants received a $50 exercise voucher three times during the intervention. The voucher could be exchanged with various sport goods such as socks, t-shirt, and soccer ball. Obesity Intervention The obesity intervention consisted of physical activity and behavior-based motivational enhancement intervention associated with physical activity. The physical activity in this study consisted of various jump rope exercises, which participants engaged in 3 times a week for 50 minutes (consisting of warm-up for 5 minutes, jump rope for 40 minutes, and cool-down for 5 minutes). The warm-up session aimed to increase participants’ interest in exercise and improve their joint mobility, and included jogging and flexibility
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LEE AND KIM TABLE 2 Obesity Intervention Obesity Intervention Psychological strategy (2 times/week)
Week
4–5
Explanation of the effect of jump rope Explanation and demonstration of how to implement jump rope Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope)
6–8
Intensity: 55–60% of HR max
9–10
Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope) Intensity: 60–65% of HR max
1–2
3
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Physical activity (3 times/week) Jump rope
11–12
13 14
15 16
Various jump rope (e.g., Single jump rope, Partner jump rope, double unders jump rope, and group jump rope in a long rope)
Intensity: 65–70% of HR max
Topic
Strategy
Understanding of obesity Goal setting
Introduction of psychological strategy Awareness of obesity-related problems Setting the target weight
Identification of current level
Physical activity test (METs score) Self-efficacy test Perceived benefits and barriers test Finding one’s reasons for not doing physical activity Discussing one’s lifestyle Setting an achievable physical activity plan Understanding the importance and effect of physical activity Finding calorie consumption by an activity type Discussing one’s physical activity habits Understanding the meaning and scope of self-efficacy Identifying the relationship between self-efficacy and physical activity Enhancing confidence for promoting physical activity Understanding the importance of motivation and perception toward physical activity Recognizing the benefits and barriers of physical activity Exploring the way to enhance motivation and perceived benefits Understanding the meaning and resources of social support Asking support from friends and families Sharing one’s thought and experiences about obesity and physical activity with others Replacing negative factors for physical activity and weight control with positive ones Setting new physical activity goal for maintaining proper weight Summarizing obesity intervention Identifying the attainment of one’s goal and rewarding for it
Identification of one’s problems Setting of new plan for behavioral change Physical activity Self-efficacy
Motivation Perceived benefits and barriers
Social support Awareness change
Setting new goal for weight control Conclusion of intervention
exercises. The cool-down session was to help return the heart rate to its normal level, and included muscle flexibility and stretching. The intensity of the jump rope exercise started at 55%–60% of maximum heart rate and gradually increased to 60%–70% of maximum heart rate. In order to promote participants’ motivation, various jump rope exercises were implemented with music. These exercises included single jump rope, partner jump rope, double unders jump rope, and group jump rope using a long rope.28 The behavior-based motivational enhancement intervention applied in this study was based on materials used in previous studies.28,29 The intervention was designed to help obese adolescents regularly participate in physical activity by employing current scientific understanding of the various psychological variables that influence weight control and corresponding strategies to modify such variables (eg, if an obese adolescent is unable to participate in physical activity on a regular basis, a psychological technique would
include offering motivational content such as accurate information about the advantages of regular physical activity). In specific, at the beginning of the intervention, awareness of perceived benefits and barriers was emphasized to raise participants’ awareness of the severity of obesity-related health problems and the benefits of physical activity. Midway through the intervention, practical techniques for enhancing self-efficacy and social support (ie, setting an achievable physical activity plan and enhancing confidence for promoting physical activity) were emphasized to help participants realize the importance of building confidence and social support to encourage regular physical activity. The final stage of the intervention emphasized motivation-based psychological reinforcement techniques (ie, setting new physical activity goal for maintaining proper weight and identifying the attainment of one’s goal and rewarding for physical activity) for each participant to continue to lose weight and to maintain regular physical activity.
OBESITY INTERVENTION WITH MALE OBESE ADOLESCENTS
Data Analysis Descriptive statistics (ie, mean and standard deviation) were conducted to summarize the participants’ characteristics. In addition, a repeated measures ANOVA was carried out to examine the change in BMI, the levels of physical activity, and psychological variables (self-efficacy, perceived benefits, and perceived barriers) over 16 weeks (p < .05). Post hoc Bonferroni-corrected tests were used to identify significant differences between each of the three time points. All statistical analyses were conducted using SPSS 18.0.
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RESULTS Effects of the Obesity Intervention on BMI and Physical Activity A repeated-measures ANOVA was carried out to examine how BMI and physical activity among participants changed over the 16-week obesity intervention and the results are shown in Table 3. Obese adolescents’ BMI consistently decreased over the 16 weeks and this was statistically significant (F D 3.51, p D .03). Moreover, across the 16 weeks, obese adolescents’ total amount of physical activity steadily increased and these changes were statistically significant (F D 4.01, p D .02). Interestingly, we found that the amount of mild physical activity (F D 7.24, p < .001) and moderate physical activity (F D 8.99, p < .001) showed significant increases across all three time points, but there was no significant change in the amount of strenuous physical activity (F D 1.31, p D 0.31). Effects of the obesity intervention on psychological variables related to physical activity Table 4 illustrates the results of the repeated measures ANOVA on whether the psychological strategy of the obesity intervention effectively improved psychological variables relating to physical activity. Results indicated that psychological variables were significantly changed over the 16-week intervention. In specific, obese adolescents’ self-efficacy (F D 5.02, p D .01) and perceived benefits (F D 5.34, p D .02) significantly increased and their perceived barriers (F D 5.10, p D .02)
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significantly decreased over the 16 weeks. In specific, obese adolescents showed significant increases in ‘weight control (F D 8.67, p < .001) and ‘better outlook’ (F D 3.67, p D .04) in perceived benefits. In perceived barriers toward physical activity, ‘physical satisfaction’ (F D 11.23, p < .001), ‘lack of competence’ (F D 4.01, p D .03), and ‘tiredness’ (F D 3.96, p D .03) were significantly reduced.
DISCUSSION Although there is a wide body of research indicating that obesity has a negative influence on health, the obesity rate is rapidly increasing across all age groups and the rise in adolescence is particularly alarming. In behavioral medicine, it has been widely supported that adolescents’ obesity is significantly associated with physical inactivity and its related psychological variables. With this background, the focus of the present study was to investigate whether an obesity intervention combining physical activity and psychological strategy can decrease BMI, improve physical activity and positively change psychological variables relating to physical activity among obese adolescents. Results indicated that obese adolescents’ BMI continuously decreased over the 16 weeks of jump rope exercises. This finding is supported by previous studies demonstrating that regular physical activity helps decrease body fat and promote weight regulation.17,30,31 In particular, because medications for obesity control have been shown to have little effect and many side effects, and as dietary regulation is not recommended to adolescents who are still growing, participation in regular physical activity is being regarded as the most effective way to reduce weight for obese adolescents.32 In addition, obese adolescents’ physical activity significantly increased across the obesity intervention. Interestingly, there was significant change in the levels of mild and moderate physical activity, but strenuous physical activity did not substantially change over the intervention. These findings can be understood by several reasons. First, on a basis of an assumption that participating in jump rope 5 days a week for the 16 weeks might not be an easy task for obese adolescents due to limitations of physical fitness,
TABLE 3 Changes in BMI and Physical Activity by the obesity Intervention
2
BMI (kg/m ) Total PA(METs) Mild PA Moderate PA Strenuous PA
Baseline1 (M § SD)
8weeks2 (M § SD)
16 weeks3 (M § SD)
Ftime
p
28.32 § 1.99 57.42 § 11.05 12.71 § 11.23 17.38 § 10.95 27.33 § 11.04
28.12 § 2.20 70.78 § 15.69 17.63 § 13.33 24.14 § 15.21 29.01 § 16.04
26.42 § 2.57 83.12 § 11.04 22.53 § 10.86 29.37 § 10.61 31.22 § 10.49
3.51 4.01 7.24 8.99 1.31
.03 .02
