Weight Loss Practice by Weight Status Among Adolescents

Abstract

Aim: To determine the association of weight status and Unhealthy Weight Loss Practice (UWLP) among 12-to-18-year-old adolescents

Methods: A cross-sectional study of 12-to-18 year olds (N=6,212) from the 2011 Youth Risk Behavior Survey in Florida was conducted. UWLP was categorized based on self-report of at least one of three methods to lose weight: 1) ≥ 24 hours of fasting, 2) diet pill use and 3) laxative use/purging. The reference group included those with no reported UWLP. Logistic regression, adjusted for demographic, substance use, and exercise variables, assessed relationships between weight status (defined by age-sex-specific body mass index percentiles) and UWLP.

Results: Analysis was restricted to 5,323 adolescents who had complete weight status information. About 13.3% of adolescents reported at least one UWLP. A quarter of the sample (25.1%) was either overweight or obese. The prevalence of UWLP was highest in obese (23.1%) and overweight (17.6%) adolescents compared to 11.1% of healthy weight adolescents. Obese and overweight adolescents were significantly more likely than healthy weight adolescents to exhibit at least one UWLP (adjusted odds ratios [AOR]=2.85, 95% confidence interval [CI]=2.17-3.74; AOR=1.66, 95% CI=1.27-2.16, respectively). Adolescents who reported tobacco (AOR=1.78, 95% CI=1.31- 2.40), alcohol (AOR=1.58, 95% CI=1.27-1.96), marijuana (AOR=1.0, 95% CI=0.72-1.39) or cocaine use (AOR=3.69, 95% CI=2.37-5.75) had higher odds of UWLP compared to non-user counterparts.

Conclusions: Overweight and obese adolescents present with higher odds of engaging in UWLP compared to healthy weight peers. These findings have important implications as the prevalence of obesity in adolescence remains a concern in Florida and in the United States.

Keywords: Adolescents; Obesity; Overweight; Unhealthy weight loss; YRBS

Abbreviations

AOR: Adjusted Odds Ratios; BMI: Body Mass Index; CDC: Centers for Disease Control and Prevention; CI: Confidence Intervals; OR: Odds Ratios; UWLP: Unhealthy Weight Loss Practice; US: United States; YRBS: Youth Risk Behavior Survey

Introduction

Obesity remains one of the top public health concerns in the United States (U.S.) [1]. Alarmingly, the prevalence of obesity among U.S. adolescents aged 12-to-19 years has quadrupled from 5% to 21% in the past 30 years [2,3]. In Florida, the proportion of overweight or obese children between the ages 10-to-17-years was 33.1% in 2007, which was higher than the nation's (31.6%) prevalence [4].

Studies have shown that obese adolescents are not only more likely to have at least one cardiovascular disease risk factor, they are also significantly more likely to exhibit negative health outcomes such as bone and joint problems, sleep apnea, and psychological problems such as poor self-esteem [5-9]. In addition, there has been a recent increase in the proportion of adolescents with type 2 diabetes corresponding to the rise of overweight status and obesity [9]. The increased risk of negative health outcomes contribute toward the rising cost of medical care, which was about $1,429 higher per year in obese people compared to those of healthy weight [9,10]. The economic burden caused by childhood obesity alone is estimated to be about $14 billion annually in direct health expenses [11,12]. When comparing children covered by Medicaid to those under private insurance, Medicaid children were about six times more likely to be treated for a diagnosis of obesity [12].

It is known that adolescence is a vital stage in development in regard to establishing health behaviors that have the potential to persist into adulthood [13]. Adolescence is a period that is gaining more recognition for weight loss interventions and treatments, such as bariatric surgery [14,15], which contributes toward the evidence that obesity during adolescence is of concern. Furthermore, previous studies have shown that the risk for eating disorders and associated weight-related behaviors are at the highest during the period of adolescence [16-18]. Adolescents with eating disorders such as anorexia nervosa and bulimia nervosa have been shown to exhibitcommon risk factors attributed to obesity such as weight and shape concerns, loss of control of food consumption, and unhealthy weight regulation behaviors [19]. Eating disorders are also increasing as a cause of morbidity and mortality in young individuals [20].

The primary aim of this study was to determine the relationship between weight status (underweight, healthy weight, overweight, and obese) and unhealthy weight loss practice among 12-to-18-year-old high school students using the Youth Risk Behavior Survey (YRBS) of Florida. We hypothesized that the prevalence of unhealthy weight loss practice differs among underweight, healthy weight, overweight and obese adolescents. We also aimed to evaluate the relationship between perceived and actual weight status among adolescents.

Methods

Study population

Study population consisted of 12-to-18-year-old students (N=6,212) from the Youth Risk Behavior Survey (YRBS) collected from Florida high schools in 2011. The YRBS is a Center for DiseaseControl and Prevention (CDC) survey administered to public high school students in the spring or fall semesters of odd-numbered years [21] that uses a two-staged, cluster sample design to select a sample representative of 9^th to 12^th grade students in its jurisdiction [22]. Details of survey administration are described elsewhere [22].

Briefly, in-class questionnaires were completed by the student on a computer-scannable format. A few in-class strategies were employed to minimize the possibility of students seeing each other's responses as they completed the questionnaire. Questionnaire booklets were sealed and placed in an unmarked envelope at end of administration to further protect response privacy [22]. According to the data collection protocol [22], students who were absent on the day the questionnaire was initially administered still had the opportunity to complete the questionnaire at a later date. This allowed for increased response rates and collection of data representative of all high school students in Florida. In 2011, Florida school, student, and overall response rates were 92%, 78%, and 75%, respectively. The corresponding national school, student, and overall response rateswere 81%, 87%, and 71%, respectively [23]. Parents of the students provided passive permission by signing a form only if they did not want their child to participate in the survey [22].

Weight loss practice

The primary outcome of interest was the Unhealthy Weight Loss Practice (UWLP) defined as those who reported one or more of three methods to lose weight: (1) ≥ 24 hours of fasting, (2) diet pill use, and (3) laxative use or purging. The response from the following questions were used to define UWLP: (1) During the past 30 days, did you go without eating for 24 hours or more (also called fasting) to lose weight or to keep from gaining weight?; (2) During the past 30 days, did you take any diet pills, powders, or liquids without a doctor's advice to lose weight or to keep from gaining weight? (Do not include meal replacement products such as Slim Fast.); (3) During the past 30 days, did you vomit or take laxatives to lose weight or to keep from gaining weight?"[24] The reference group was defined as students who reported none of the three aforementioned methods to lose weight or to keep from gaining weight.

Weight status

Perceived weight status was categorized into three groups (underweight, healthy weight, and overweight) from five original response options based on the following question: "How do you describe your weight?" (very underweight, slightly underweight, about the right weight, slightly overweight, and very overweight) [24]. Very underweight and slightly underweight were grouped as "underweight"; about the right weight was grouped and named as "healthy weight"; and slightly overweight and very overweight were grouped as "overweight". Actual weight status was defined using the CDC standardized age-sex-specific Body Mass Index (BMI) percentiles based on self-reported height and weight. Underweight, healthy weight, overweight, and obese were defined as less than the 5^th percentile, 5^th percentile to less than the 85^th percentile, 85^th to less than the 95^th percentile and equal to or greater than the 95^th percentile of BMI, respectively [25].

Covariates

Gender, age, race/ethnicity, grade, substance use, and exercise performed were considered covariates a priori. The YRBS captured gender as male/female and age as 12 years old or younger, 13 years old, 14 years old, 15 years old, 16 years old, 17 years old, and 18 years old or older. Race/ethnicity was defined as White, Black or African American, Hispanic, American Indian/Alaska Native, Asian, and Native Hawaiian/Other Pacific Islander. Due to small sample size, American Indian/Alaska Native, Asian, and Native Hawaiian/Other Pacific Islander were combined to create an "other" race/ethnic group. The current grade level in school was classified as 9^th, 10^th, 11^th, and 12^th grade, as well as ungraded or other grade [24]. Substance use, including cigarette, alcohol, marijuana and cocaine use were defined using the following questions: "(1) During the past 30 days, on how many days did you smoke cigarettes?; (2) During the past 30 days, on how many days did you have at least one drink of alcohol?; (3) During the past 30 days, how many times did you use marijuana?; (4) During the past 30 days, how many times did you use any form of cocaine, including powder, crack, or freebase?". Cigarette, alcohol, marijuana, and cocaine use were treated as individual binary variables (1=use, 0=no-use) in current analysis. Exercise, treated as a continuousvariable, was defined as the number of days per week having 20 minutes of vigorous exercise or 30 minutes of moderate exercise [24].

Statistical analysis

Statistical Analytic Software (SAS) version 9.3 (SAS Institute, Inc., Cary, North Carolina) was used for all analyses. The sampling design, weight and non-response effects were taken into account in all analyses. Weighted survey frequencies and Rae-Scott Chi-Square tests were used to compare demographic, school performance, substance use and unhealthy weight loss method differences between weight status groups (underweight, healthy weight, overweight, and obese). ANOVA was used to compare the mean days of exercise between groups. Both univariate and multivariable logistic regression were used to evaluate the association between UWLP and selected demographics (age, gender, race/ethnicity, and grade), school performance, behavioral variables (cigarette, alcohol, marijuana and cocaine use, exercise), and weight status. Results are reported as unadjusted and adjusted odds ratios (AOR) with 95% Confidence Intervals (CI). All tests were performed at a significance level of 0.05.

Result

Sample characteristics

The sample (N=6,212) represented 787, 657 public high school students (grades 9-12) in Florida. Analysis was restricted to 5,323 (weighted N=678,193) students with complete weight status information (889 students had missing weight status). Overall, there were more males (50.4%) and whites (47.3%) than their respective counterparts in the entire sample. The majority of the sample (> 64%) was 16 years of age or older in each weight status group.

About 14.0%, 37.3%, 22.3% and 2.7% of the adolescents reported smoking cigarette, drinking alcohol, using marijuana or cocaine respectively. There were no significant differences of cigarette smoking, alcohol and cocaine use cross the four weight status groups. Obese adolescents had the highest (25.0%) and overweight adolescents had the lowest (17.8%) proportion of marijuana use. There were no significant differences in exercise frequency among the four weight status groups. Detailed demographic characteristics byweight status groups are described in Table 1.