Inventory of Determinants of Obesity-Related Behaviors in Adolescents: Development and Psychometric Characteristics

The rising prevalence of childhood obesity is a major health problem worldwide (1, 2). Increasing evidence reveals that overweight children are at increased risk for various chronic diseases later in life (3). The latest national data in the United States suggest a 17% prevalence of childhood obesity (4). In Iran according to the childhood and adolescence surveillance and prevention of Iranian adult non-communicable disease (CASPIAN) study, more than 8.8% of school-age children are presently overweight and another 4.5% are obese (5). Additionally, findings of recent cross-sectional studies conducted in Tehran indicated that overweightness and obesity are highly prevalent among adolescents residing in Tehran (6, 7). In the study conducted by Hatami et al. on 1157 adolescents, 20.7% were overweight or obese (6). Another study by Jalali-Farahani et al. on 465 high school students showed that 38.5% of them were overweight or obese (7). These findings have led to a widely held view that pediatric obesity interventions are urgently required.

Behavioral strategies are considered the first line of implementation for obesity prevention in the early years of life (8). Previous quantitative studies in Iran primarily have described obesity-related behaviors in adolescents, without much insight to why they are engaged in such behaviors (9-11). Accordingly, there are related reviews demonstrating significant numbers of youth obesity interventions that have demonstrated modest results so far (12-14). Hence, there is a growing need for health professionals to become capable of assessing the factors that determine lifestyle in a culturally relevant manner.

There are several instruments already developed to assess lifestyle in children and adolescents (15-18); however, prior to the Inventory Determinants of Obesity-Related Behaviors in Adolescents (IDOBA), there was no known instrument to assess the culturally relevant determinants of obesity-related behaviors in Iranian adolescents. The IDOBA was developed to fill the gap in current literature available on measures previously developed.

This study aimed to develop and assess validity and reliability of the IDOBA, in a diverse sample of overweight and obese adolescent residents of Tehran, Iran.

2.1. The Conceptual Framework

The conceptual framework for this study was based on the results of a qualitative research, using a grounded theory approach with participation of 51 overweight/obese adolescents (19). This framework hypothesizes that influenced by socio-environmental factors and personal characteristics, predisposing beliefs in adolescents form the basis, which results in their unhealthy lifestyles. These beliefs include perception of educational achievement priority, acceptability, lack of threat, and inability to control weight, which induces a psychologic condition that decreases adolescent motivation towards healthy behaviors (Figure 1).

Figure 1.

Conceptual Framework of Weight Gain Process in Studied Adolescents

A total of 478 adolescents (57.7% male) aged 13 to 18 years participated in the study. Mean BMI was 30.25 ± 4.22 kg/m². Levels of education, occupation status of parents, and their mean age are reported in Table 1. Most fathers and mothers were educated up to secondary levels (38.1% and 50.1%, respectively). Most fathers had non-governmental jobs (64.6%), whereas the highest proportions of mothers were House wife (79.9%).

Based on the face validity results, all questionnaire items were generally easy to read and understand for adolescents; however, a few words were changed to meet participants’ considerations. Of 91 items, 89 (97.8%) were labeled as “important” to them. Qualitative content validity was confirmed by the panel of experts and findings regarding the CVR and CVI confirmed the quantitative content validity of 75 items. The CVR in this study for total scale was 0.82, indicating a satisfactory result. A satisfactory level of agreement was found (CVI = 0.92) among panelists suggesting that the scale had a good content validity. No floor effects were observed. Detected ceiling effects ranged from 2.7% for perceived priority of educational achievement subscale score to 12.9% for stress-related eating.

In case of EFA, KMO showed a reasonable fit of the model (KMO = 0.78), and the Bartlet’s test confirmed the sphericity assumption (χ² = 5469.4, df = 946, and P < 0.001). The extracted eight factors were based on eigenvalues > 1.25. The percentage of the total variance was 49.06% by the rotated eight factors. Factor loadings and explained variance of each factor are illustrated in Table 2. All items were loaded between 0.30 and 0.89 on their corresponding factors. The results of the CFA for eight-factor hypothesized model are reported in Table 3 and indicate acceptable fit of the proposed model. Minimum factor loadings was 0.12 (t = 6.56) for question number 7 (from the unhealthy nutrition and physical activity subscale) and maximum factor loadings was 0.99 (t = 33.88) for question number 14 (from the perceived inability subscale).

The mean of subscale scores and number of items in each subscale are presented in Table 4. To calculate subscale scores, all items in the corresponding subscale were summed and transformed to a zero to 100 scale. No ceiling effects were observed. Detected floor effects ranged from 0.2% for perceived acceptability subscale score to 18.8% for lack-of-threat subscale score. The Cronbach’s alpha was calculated for each subscale and ranged from 0.61 to 0.81. Minimum and maximum ICC of items in each subscale are reported in Table 4; question No. 16 from the perceived acceptability subscale had low ICC, which could be due to the long interval between test and retest measurement.

Our results indicated that the IDOBA facilitates a reliable and valid measurement of determinants of obesity-related behaviors in Tehranian adolescents. Its internal consistency reliabilities generally exceeded the standard of 0.70, and all subscales demonstrated satisfactory test-retest reliability, consistent with other similar self-reporting measures (17, 26, 27).

Research on explanations of the obesity-related behaviors process in adolescents has been less extensive than that on description of these behaviors, as it is hindered by a lack of related conceptual frameworks. Accordingly, there is a lack of empirical instruments to assess lifestyle determinants in the earlier years of life. Among the available instruments, each of the adolescent life style questionnaire (ALQ) and the Adolescent Lifestyle Profile (ALP) focus on seven domains of a healthy life style in adolescents (16, 17). Moreover, a recently reported questionnaire, HABITS, was developed to assess pediatric lifestyle and weight management by measuring children’s food intake and physical activity/sedentary behavior (15). There is also another instrument, the Life Style Behavior Checklist (LBC), developed to measure parents’ challenges faced in managing their children behaviors and how these challenges might be addressed in treatment (18).

As a theory-based questionnaire, the IDOBA differs from the earlier mentioned instruments, which focused mainly on measuring sedentary behaviors or barriers to healthy lifestyles in children and adolescents. Recent evidence about moderate goal achievements of childhood obesity prevention programs indicates that these efforts should be based on culture related knowledge (12-14). Based on this premise, all items of the IDOBA were designed and developed to measure potential factors that contribute to decreased adolescent motivation regarding healthy behaviors according to a context-based conceptual framework. This framework indicates the central role of motivation loss that results in obesity-related behaviors and excessive weight gain in adolescents in Tehran. This motivation loss could be a result of adolescents’ beliefs and perceptions, including prioritized educational achievement, acceptability, inability for weight control, and lack of threat, which are affected by certain socio-environmental and personal characteristic (19). However, the items of the IDOBA are not unique to Iranian adolescents and could be relevant for other ethnic groups, which would require basic but essential assessments.

The IDOBA is a simple instrument, which is developed for researchers and healthcare professionals to assist in identifying the underpinning factors of obesity-related behaviors in adolescents in Tehran and to developing prevention programs to overcome barriers to a healthy lifestyle. However, the generalizability of the current findings are limited for the following reasons:

1) The participants of this study were limited to urban Tehranian adolescents; 2) The information of nonparticipants was not available; and 3) Due to limited access to socio-economic data, the studied population could not be considered as a representative sample of adolescents from different socio-economic statuses in Tehran.

In conclusion, the IDOBA was designed to measure determinants of obesity-related behaviors in adolescents, based on the conceptual constructs that emerged from the initial qualitative study and a literature review. To confirm its current validity results, further evaluation with larger Iranian rural and urban populations with different socio-economic statuses is recommended.