J Youth Adolescence (2009) 38:1364–1373 DOI 10.1007/s10964-009-9421-0
EMPIRICAL RESEARCH
Associations Between Smoking and Extreme Dieting Among Adolescents Dong-Chul Seo Æ Nan Jiang
Received: 11 April 2009 / Accepted: 22 May 2009 / Published online: 7 June 2009 Ó Springer Science+Business Media, LLC 2009
Abstract This study examined the association between cigarette smoking and dieting behaviors and trends in that association among US adolescents in grades 9–12 between 1999 and 2007. Youth Risk Behavior Survey datasets were analyzed using the multivariable logistic regression method. The sample size of each survey year ranged from 13,554 to 15,273 with girls representing 49–51% of the sample (N = 71,854). About 62% of the entire study participants were whites and 14% were blacks. Prevalence estimates of current smoking and corresponding 95% confidence intervals were computed across four comparison groups formed by gender and body weight. Extreme dieting was an independent predictor of smoking. Extreme dieters showed a higher variability of smoking behavior than their peers. The magnitude of the association between smoking and extreme dieting became smaller in recent years among adolescents but remained unchanged among non-overweight girls over that same time period. When adolescent smoking behavior is examined, the intensity of dieting behavior should be considered within its association with other co-occurring unhealthy behaviors. Keywords Current smoking Extreme dieting Overweight Adolescent health
Introduction Smoking and extreme dieting appear to be two distinct behaviors. However, they share commonalities. Both D.-C. Seo (&) N. Jiang Department of Applied Health Science, Indiana University, 1025 E. Seventh Street, Bloomington, IN 47405, USA e-mail:
[email protected]
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behaviors can lead to acute or chronic morbidity or mortality (Centers for Disease Control and Prevention (CDC) 1994; DeBate et al. 2006). Both are related to certain psychological attributes (Cosci et al. 2009; Martyn-Nemeth et al. 2009). And more importantly, both behaviors are commonly initiated in adolescence (CDC 2009a; Seo et al. 2008). If the two behaviors co-occur in adolescents, detrimental health effects may be synergistically exacerbated, endangering the health of youths who are still physically and mentally in the developmental stage. Thus, a good understanding of the link between smoking and extreme dieting behaviors among adolescents is imperative to expand our understanding of adolescents at risk and advance prevention efforts. Smoking remains the leading preventable cause of death in the United States (CDC 2002). The results of the Youth Risk Behavior Survey (YRBS) show that the rate of current cigarette smoking among students in grades 9–12 has declined from 23.0 to 20.0% between 2005 and 2007 (CDC 2008a). But the rate of 20.0% was still greater than the national health objective for 2010, which is B16.0% (objective no. 27-2b) (U.S. Department of Health and Human Services [DHHS] 2001). The salient risk factors for adolescent smoking include weight concern and weight status (Cawley et al. 2004) in addition to peer influence, perceived stress and parental smoking (Nichter et al. 1997). Increasing evidence reveals that actually being overweight or being perceived as such is an independent predictor for cigarette smoking among adolescents (Seo et al. 2009; Weiss et al. 2007) and that the association between smoking and weight concern among US adolescents strengthens between 1999 and 2005 (Seo, Jiang, Kolbe). Therefore, adolescent smoking behavior should be examined in relation to their weight concern and weight status.
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Weight concern and weight status, in turn, predict dieting behaviors among adolescents, which include anorexia nervosa, bulimia nervosa and binge-eating disorder (Boutelle et al. 2002; Jones et al. 2001). The high prevalence of extreme dieting behaviors among adolescents, such as fasting, taking diet pills, vomiting, or using laxatives to lose weight, is still an apparent concern (Chao et al. 2008). The 2007 YRBS results show that 11.8, 5.9, and 4.3% of the adolescents engage in fasting, taking diet pills, and vomiting, respectively (CDC 2008b). One might reasonably assume that smoking is directly associated with dieting behaviors among adolescents given the strong association of weight concern with both dieting behaviors and smoking in this population. A large body of research has demonstrated that cigarette smoking is likely to co-occur with extreme dieting behaviors among adolescents. In a study among Minnesota public school students in grades 7–12, French et al. (1995) concluded that purging and tobacco use co-occurred among both boys and girls. Story et al. (1997) reported the same result in a study among Native American youths in those same grades. A study of US high school seniors by Gritz and Crane (1991) found that both male and female smokers were more likely to use diet pills than nonsmokers. And Neumark-Sztainer et al. (1996) concluded that, among Minnesotan adolescents in the 6th, 9th, and 12th grades, both boys and girls who used extreme dieting methods (including vomiting and use of laxatives, diuretics, and diet pills) were more likely to engage in cigarette smoking than those who did not use such methods. The results of the 1993 YRBS showed that both boys and girls who engaged in vomiting or taking diet pills were more likely to use tobacco than those who did not engage in extreme dieting behaviors (NeumarkSztainer et al. 1998). Krahn et al. (1992) noted in a female-only study that increased dieting severity was positively associated with cigarette smoking. This was affirmed by another female-only study among Connecticut public school students in the 7th, 9th and 11th grades (Sherwood et al. 2002) where girls with eating disorders were found to smoke more than girls who did not report such disorders. All of these findings converge on the fact that cigarette smoking tends to co-occur with extreme dieting behaviors among adolescents. Contradictory findings on the association between smoking and extreme dieting are also noted in the literature. Patton et al. (1998) reported negative relationships between smoking and severe dieting status among 14- to 15-year-old boys and girls in Victoria, Australia. In a study among middle school students in North Carolina, Krowchuk et al. (1998) reported that vomiting and smoking were predictive of each other among boys but showed no association among girls. Neumark-Sztainer and Hannan (2000),
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however, found in a study among adolescents in grades 5–12 that disordered eating was more likely to co-occur with smoking among girls, but not among boys. In a Canadian study, Winter et al. (2002) noted that skipping meals and smoking were predictive of each other among adolescent boys and girls, but the positive association of smoking with vomiting and taking diet pills was observed in girls only. No association of smoking with vomiting and taking diet pills was detected among boys in that study. The literature is inconclusive on the association between smoking and extreme dieting among adolescents. The contradictory findings necessitate a corroboration of the relationship between smoking and dieting behaviors among adolescents using a nationally representative sample. Very few of the previous studies used such a sample of adolescents to examine this association. This article aims to use years of data from nationally representative samples of US adolescents to examine the current relationship between cigarette smoking and extreme dieting (fasting; taking diet pills, powders, or liquids without a doctor’s advice; or vomiting or taking laxatives). The connection between smoking and other less extreme weight control behaviors, such as mild dieting (eating less food, fewer calories, or foods low in fat) and exercise will also be examined by this study. Whether the association between smoking and extreme dieting has been stronger, weaker, or has remained unchanged over time, requires consideration as well, as no study to date has examined such trends. By investigating the magnitude of this association among adolescents from 1999 to 2007, this study will expand the body of research. And, as a result, these findings may provide information helpful to understanding the patterns of smoking among adolescents engaging in weight control behavior and aid smoking intervention development for this group.
Hypotheses Based on the findings of prior studies, though contradictory in nature, it is hypothesized that adolescents who engage in either mild or extreme dieting behaviors are at an increased risk of cigarette smoking than those who do not. Due to a lack of research on this topic, no prior hypothesis exists regarding the magnitude change in the association between current smoking and extreme dieting behaviors among adolescents between 1999 and 2007. An exploratory hypothesis of this study (i.e., no prior studies have been conducted to test this hypothesis) is that there exists a higher variability of smoking behavior among extreme dieters than adolescents who do not engage in extreme dieting. Contradictory findings in the previous studies are believed to be due, in part, to the higher
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heterogeneity of smoking behavior among extreme dieters than those who do not engage in extreme dieting. If previous studies did not have an adequate sample size, let alone the use of a representative sample, they might have failed to capture the true relationship due to increased possibility of Type II error. Given that only about 20% of the adolescent population is smokers and that extreme dieters comprise a much smaller proportion of the general population, the sample size issue (i.e., statistical power) becomes more relevant. Higher heterogeneity in the outcome variable may easily lead to contradictory findings if the sample size is not adequate or the sample is not representative due to the increased chance of capitalizing on chance variation. Because this study employs a large nationally representative sample of US adolescents, this exploratory hypothesis is likely to be tested with less bias.
Method Sample Data was derived from the YRBS, a school-based paperand-pencil survey designed to monitor six priority healthrelated behaviors among public and private high school students in the United States (CDC 2004). The YRBS is an anonymous, confidential survey administered by the Centers for Disease Control and Prevention (CDC) every 2 years. The sample for this study was composed of multiple years of cohorts from the 1999 to 2007 YRBSs, which employed a three-stage cluster sampling design to produce a nationally representative sample of students in grades 9–12. In the initial stage, primary sampling units (PSUs) were listed and categorized into 16 strata according to metropolitan statistical area status and proportion of students with black and Hispanic origin. Each PSU consisted of large counties, subareas of large counties, or groups of smaller, adjacent counties. Among these PSUs, 52–57 were selected in each survey year. In the second stage, schools with any of the grades 9–12 were selected with a probability proportional to school enrollment size. In the final stage, one or two classrooms were randomly selected in each chosen school and in each of grades 9–12. All students in the chosen classes were invited to complete the survey and participation was completely voluntary. Schools, classes, and students that refused to participate were not replaced. A weighting factor was applied to each student record to adjust for nonresponse and different probabilities of selection, including those resulting from oversampling of black and Hispanic students. Additional details about the YRBS may be obtained from other sources (CDC 2004).
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Measures Current Smoking Status Current smoking was assessed with the question ‘‘During the past 30 days, on how many days did you smoke cigarettes?’’ According to the CDC’s definition (CDC 2000), students who did not smoke a cigarette during the past 30 days were considered non-smokers. Those who reported smoking cigarettes on at least one of the 30 days preceding the survey were considered current smokers. Weight Control Behaviors Weight control behaviors were assessed with five questions (CDC 2009b). Exercise was assessed with the question ‘‘During the past 30 days, did you exercise to lose weight or to keep from gaining weight?’’ Mild dieting was measured by the question ‘‘During the past 30 days, did you eat less food, fewer calories, or foods low in fat to lose weight or to keep from gaining weight?’’ Extreme dieting was measured by three separate questions: (1) ‘‘During the past 30 days, did you go without eating for 24 h or more (also called fasting) to lose weight or to keep from gaining weight?’’ (hereafter referred to as ‘‘fasting’’); (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.)’’ (hereafter ‘‘taking diet pills’’); (3) ‘‘During the past 30 days, did you vomit or take laxatives to lose weight or to keep from gaining weight?’’ (hereafter ‘‘vomiting’’). The response options to all five questions above were ‘‘Yes’’ or ‘‘No.’’ Respondents who reported ‘‘Yes’’ to any of the three extreme dieting questions were considered ‘‘extreme dieters.’’ Control Variables Control variables include body weight status, gender, and race. Body mass index (BMI) was calculated by selfreported height and weight. A BMI percentile rank which indicates the relative position of an adolescent’s BMI adjusted for gender and age was obtained based on the CDC’s growth charts (CDC 2008c). Although the CDC distinguishes overweight (BMI C 95th percentile) from at risk of being overweight (85th B BMI \ 95th percentile), this study combined the two groups together as one (BMI C 85th percentile) for this study due to the small cell size of extreme dieters. Therefore, in this study, respondents with a BMI equal to or greater than the 85th percentile were placed into the ‘‘overweight’’ group and those with a BMI below the 85th percentile into the ‘‘non-overweight’’ group. Based on weight group and gender, four
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groups were created: non-overweight girls, overweight girls, non-overweight boys, and overweight boys. Given the low frequency of some race categories (e.g., only 0.6– 1.0% of the adolescents are native Hawaiian or other Pacific islanders), this study collapsed the responses into three race groups: white, black, and others. Statistical Analysis All the analyses were conducted using STATA version 10.0. After unweighted frequencies and weighted percentages of variables were examined, multivariable logistic regressions were performed to calculate adjusted odds ratios, controlling for grade and race to examine trends in current smoking and each weight control behavior between 1999 and 2007 across the four groups. Multivariable logistic regression was also performed to test the association between current smoking and each weight control behavior by survey year across the four groups. In each group, prevalence estimates for current smoking and corresponding 95% confidence intervals (CIs) were computed across groups of extreme dieter and non-extreme dieters to test the difference in group percentages by survey year. The group percentage differences are statistically significant if the 95% CIs do not overlap.
Results Table 1 shows unweighted frequencies and weighted percentages of variables among US adolescents by survey year. An overall decreasing smoking rate and an increasing exercise rate are noted between 1999 and 2007. The prevalence of fasting remained unchanged over time. Mild dieting rate increased between 1999 and 2001, and decreased afterward. The rates in vomiting and taking diet pills remained unchanged until 2003 and decreased afterward. Table 2 shows unweighted frequencies and weighted percentages of current smoking and five weight control behaviors by survey year across the four groups. Unlike the overall decrease in adolescent smoking over the survey years, the smoking rate among overweight boys did not decrease since 2003. The prevalence of mild dieting among overweight boys increased over the years whereas it remained unchanged or decreased for other adolescents. In terms of extreme dieting, such as fasting, taking diet pills, or vomiting, the four groups exhibited distinctly different patterns. Overall, the prevalence of extreme dieting showed a linear downward trend among nonoverweight girls, and showed a negative quadratic trend among non-overweight boys, increasing from 1999 to 2003 and then decreasing from 2003 to 2007. A parallel
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pattern was observed over time in the movement of the three extreme dieting behaviors for non-overweight boys and girls. However, overweight boys and girls showed non-parallel patterns in the movement of extreme dieting behaviors. Whereas the prevalence of fasting and vomiting among overweight girls was stable over the years, the prevalence of taking diet pills among overweight girls showed a linear downward trend except for a surge in 2001. For overweight boys, the prevalence of fasting remained stable over the years. The prevalence of taking diet pills or vomiting among overweight boys stayed stable from 1999 to 2003 and then decreased from 2003 to 2007. In a comparison between boys and girls within the same weight category, the prevalence of exercise and mild and extreme dieting was higher among girls than in the counterpart boys. Table 3 shows the results of multivariable logistic regression of current smoking on weight control behaviors by survey year across the four groups. Overall, after adjusting for grade and race, adolescents who engaged in extreme dieting were more likely to smoke than their counterparts who reported no extreme dieting. Specifically, those who fasted or took diet pills to lose weight or to keep from gaining weight were consistently more likely to smoke than their counterparts regardless of survey year and their gender and weight status, except for overweight boys who took diet pills in 2001. Since 2005, all three extreme dieting behaviors were associated with current smoking regardless of gender and weight status. Interestingly, mild dieting was not associated with current smoking for any survey year among overweight boys and girls, whereas mild dieting was associated with current smoking for most survey years among non-overweight boys and girls. It is noted, however, that the directionality of the association was not always the same between boys and girls. Nonoverweight girls who reported mild dieting were more likely to smoke but non-overweight boys who reported mild dieting were less likely to smoke until 2003. But, since 2005, non-overweight boys reversed the direction with regard to their smoking behavior. In general, exercise showed little association with current smoking among adolescents. Figure 1 shows the trend in the association between current smoking and extreme dieting behavior from 1999 to 2007 across the four comparison groups. In general, extreme dieters showed a higher variability of current smoking rate (as measured by 95% CI) than non-extreme dieters. Extreme dieters also showed a significantly higher current smoking rate than non-extreme dieters. The difference in smoking rates between extreme dieters and nonextreme dieters has fallen in recent years since 2005 except for the non-overweight girls in which the difference remained stable across the survey years.
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Table 1 Frequencies and weighted percentages of US adolescents, 1999–2007 Youth Risk Behavior Survey (N = 71,854) Variable
1999 N (%)
2001 N (%)
2003 N (%)
2005 N (%)
2007 N (%)
Gender Female
7,828 (49.61)
6,952 (51.27)
7,544 (48.59)
7,193 (49.47)
7,036 (49.49)
Male
7,445 (50.39)
6,602 (48.73)
7,598 (51.41)
6,664 (50.53)
6,992 (50.51)
9th grade
3,786 (28.89)
3,328 (29.74)
3,674 (29.38)
3,333 (29.02)
3,467 (29.02)
10th grade
3,787 (26.02)
3,390 (25.89)
3,770 (26.08)
3,470 (25.91)
3,482 (26.24)
11th grade
3,885 (23.55)
3,517 (23.07)
3,810 (23.33)
3,529 (23.31)
3,480 (23.38)
12th grade
3,823 (21.44)
3,290 (21.20)
3,864 (21.01)
3,510 (21.63)
3,529 (21.32)
Grade
Ungraded/other grade Race White
15 (0.10)
17 (0.10)
25 (0.20)
16 (0.13)
14 (0.05)
5,407 (60.82)
6,336 (67.53)
6,585 (61.37)
6,122 (61.95)
5,775 (59.27)
Black/African American
4,283 (14.12)
2,614 (12.97)
3,590 (13.87)
3,347 (14.64)
2,931 (14.78)
Others
5,518 (25.06)
4,451 (19.49)
4,921 (24.76)
4,217 (23.41)
5,335 (25.95)
10,263 (65.19)
9,620 (71.54)
11,111 (78.09)
10,411 (77.00)
10,734 (80.00)
4,549 (34.81)
3,340 (28.46)
3,224 (21.91)
2,873 (23.00)
2,589 (20.00)
378 (2.31)
364 (3.11)
303 (2.08)
258 (1.95)
265 (2.01)
10,239 (72.71)
8,930 (72.93)
9,629 (71.04)
8,840 (68.53)
8,723 (69.22)
3,389 (24.98)
3,320 (23.96)
3,944 (26.87)
4,021 (29.53)
4,074 (28.78)
Yes
8,640 (58.43)
7,776 (59.86)
8,415 (57.05)
8,254 (60.02)
8,288 (60.94)
No
6,554 (41.57)
5,650 (40.14)
6,511 (42.95)
5,473 (39.98)
5,431 (39.06)
Yes
5,904 (40.45)
5,548 (43.79)
5,945 (42.18)
5,538 (40.68)
5,455 (40.64)
No Fasting
9,263 (59.55)
7,768 (56.21)
8,799 (57.82)
8,179 (59.32)
8,279 (59.36)
Current smoking status Non-smoker Current smoker BMI group Underweight Normal Overweight Exercise
Mild dieting
Yes
1,850 (12.56)
1,750 (13.49)
1,898 (13.26)
1,659 (12.30)
1,597 (11.76)
No
13,368 (87.44)
11,567 (86.51)
12,856 (86.74)
11,638 (87.70)
11,636 (88.24)
Taking diet pills Yes
1,071 (7.62)
1,215 (9.17)
1,246 (9.21)
No
14,127 (92.38)
12,236 (90.83)
13,576 (90.79)
862 (6.31) 12,877 (93.69)
793 (5.86) 12,542 (94.14)
Vomiting Yes No
714 (4.84) 14,474 (95.16)
714 (5.43) 12,699 (94.57)
Discussion This study’s findings bolster the primary hypothesis regarding the association between smoking and dieting behaviors. Extreme dieters were more likely to be current smokers among boys and girls as hypothesized, which is in concert with previous findings (French et al. 1995; Gritz and Crane 1991; Neumark-Sztainer et al. 1996, 1998; Story et al. 1997). This is especially alarming because detrimental health effects of smoking and extreme dieting may be synergistically exacerbated, endangering the health of
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857 (6.02) 13,940 (93.98)
639 (4.48) 13,053 (95.52)
607 (4.27) 13,128 (95.73)
adolescents who are still physically and mentally in the developmental stage. The Surgeon General lists eating disorders as one of the nine most serious mental disorders affecting US children and adolescents (DHHS 1999). People with eating disorders have the highest mortality rate among any individuals who are mentally ill, many of them dying from suicide, heart problems, or other complications (DeBate et al. 2006). Given that adolescents who engage in extreme dieting show higher rates of smoking which tends to be addictive, this group of adolescents deserve increased attention and care from health professionals.
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Table 2 Current smoking and weight control behaviors by gender-weight group among US adolescents, 1999–2007 Youth Risk Behavior Survey (N = 71,854) Variable
1999 N (%)
2001 N (%)
2003 N (%)
2005 N (%)
2007 N (%)
Change from 1999 to 2007a
Non-overweight girls Current smoking
1,751 (35.55)
1,246 (26.92)
1,119 (21.54)
957 (21.67)
823 (17.38)
;
Exercise
3,609 (64.05)
3,419 (66.28)
3,372 (63.13)
3,232 (63.56)
3,135 (63.88)
–
Mild dieting
2,800 (51.85)
2,780 (55.26)
2,692 (52.29)
2,449 (49.33)
2,351 (49.19)
– for 1999–2001 ; for 2001–2007
Fasting Taking diet pills
947 (17.77) 466 (9.48)
907 (17.63) 533 (10.46)
886 (16.89) 513 (10.25)
753 (15.36) 296 (6.15)
703 (14.33) 292 (6.17)
; ;
Vomiting
365 (7.04)
378 (7.41)
415 (8.17)
294 (5.42)
276 (5.38)
;
465 (32.31)
360 (31.60)
354 (23.36)
409 (26.96)
344 (23.08)
;
Exercise
1,283 (81.13)
1,056 (78.59)
1,276 (75.60)
1,455 (78.88)
1,297 (77.40)
–
Mild dieting
1,168 (73.43)
965 (74.48)
1,169 (71.42)
1,289 (71.26)
1,138 (66.49)
–
Fasting
375 (23.05)
327 (26.31)
400 (23.75)
389 (22.00)
375 (22.68)
–
Taking diet pills
264 (16.55)
294 (22.98)
257 (15.55)
249 (14.01)
193 (11.92)
: for 1999–2001
Vomiting
156 (9.54)
131 (9.64)
176 (9.37)
148 (8.41)
146 (9.66)
–
Overweight girls Current smoking
; for 2001–2007 Non-overweight boys Current smoking
1,661 (36.38)
1,200 (29.02)
1,226 (21.76)
990 (22.00)
921 (19.93)
;
Exercise
2,189 (40.98)
1,898 (41.84)
2,212 (41.37)
1,995 (43.23)
2,141 (45.12)
:
Mild dieting
922 (18.09)
886 (20.00)
1,000 (20.11)
825 (18.11)
870 (18.32)
–
Fasting
297 (5.26)
302 (6.29)
358 (7.31)
276 (5.92)
294 (5.61)
: for 1999–2003 ; for 2003–2007
Taking diet pills
164 (2.89)
195 (3.95)
254 (5.52)
172 (3.89)
170 (3.11)
: for 1999–2003
Vomiting
127 (1.96)
133 (2.79)
169 (3.60)
118 (2.55)
120 (2.07)
; for 2003–2007 : for 1999–2003 ; for 2003–2007 Overweight boys Current smoking
; for 1999–2003
649 (30.21)
521 (29.84)
508 (22.03)
500 (25.01)
497 (24.22)
1,517 (72.19)
1,385 (74.81)
1,523 (68.59)
1,546 (74.03)
1,707 (77.23)
:
Mild dieting
987 (43.25)
903 (49.38)
1,065 (51.43)
954 (45.72)
1,091 (50.82)
:
Fasting
220 (9.41)
211 (10.99)
247 (11.62)
233 (11.25)
223 (11.01)
–
Taking diet pills
171 (8.45)
189 (9.67)
211 (11.21)
142 (6.07)
137 (6.77)
– for 2003–2007 Exercise
– for 1999–2003 ; for 2003–2007
Vomiting
63 (2.77)
69 (3.34)
93 (4.13)
73 (3.28)
63 (2.38)
– for 1999–2003 ; for 2003–2007
The symbol : indicates an increase, ; a decrease, and – no change a
Based on trend analyses using a logistic regression model, controlling for grade and race
Whereas extreme dieters consistently showed higher smoking rates across all the survey years for all the four groups than their counterparts, mild dieters did so only during 2001–2005 for non-overweight girls and in 2005 for non-overweight boys. In the most recent survey year (2007), none of the mild dieters showed higher smoking rates across all the four groups than their counterparts. This indicates that the intensity of dieting behaviors should be
considered when adolescents’ smoking behavior is examined. Compared to extreme dieters, mild dieters are less susceptible to smoking. Smoking appears to be one of the many weight control strategies for adolescents who engage in extreme dieting, but not so for mild dieters. This affirms previous findings (Camp et al. 1993; Cavallo et al. 2006) and might indicate that extreme dieting is a better predictor of smoking than mild dieting. One explanation of this
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Table 3 Logistic regression of current smoking on weight control behaviors among US adolescents, 1999–2007 Youth Risk Behavior Survey (N = 71,854) Variable
Non-overweight girls
Overweight girls
Non-overweight boys
Overweight boys
AOR
AOR
AOR
AOR
95% CI
95% CI
95% CI
95% CI
1999 Exercise
1.03
0.77–1.38
0.84
0.48–1.47
0.73**
0.59–0.91
0.94
0.61–1.43
Mild dieting Extreme dieting
1.17
0.98–1.40
1.01
0.63–1.63
0.74*
0.56–0.97
1.20
0.82–1.77
2.96***
2.35–3.74
2.59**
1.51–4.46
1.62*
1.08–2.42
1.63*
1.05–2.54
Fasting Taking diet pills
3.58***
2.43–5.29
2.71***
1.72–4.29
2.66**
1.49–4.73
2.41*
1.11–5.22
Vomiting
1.97
0.97–4.00
4.27***
2.41–7.55
5.64**
1.95–16.32
5.39**
2.12–13.74
2001 Exercise
1.01
0.86–1.20
1.07
0.76–1.52
0.88
0.70–1.12
0.80
0.59–1.08
Mild dieting
1.18*
1.01–1.38
0.98
0.78–1.22
1.17
0.89–1.54
0.84
0.61–1.15
Fasting
2.66***
2.07–3.43
3.37***
2.52–4.51
2.55***
1.85–3.51
1.71**
1.15–2.54
Taking diet pills
3.32***
2.56–4.31
2.41***
1.65–3.53
2.64**
1.46–4.79
1.34
0.88–2.05
Vomiting
3.65***
2.61–5.10
2.57**
1.51–4.40
5.21***
2.38–11.39
4.04**
1.68–9.71
Exercise
1.10
0.90–1.34
1.04
0.60–1.80
0.77
0.59–1.01
1.11
0.64–1.94
Mild dieting
1.56***
1.27–1.91
1.04
0.77–1.41
0.69*
0.50–0.94
1.04
0.80–1.34
Extreme dieting Fasting
Extreme dieting
2003
3.12***
2.38–4.11
2.67**
1.52–4.67
1.58*
1.05–2.38
2.15**
1.40–3.29
Taking diet pills
3.73***
2.63–5.29
3.17***
1.92–5.22
1.67*
1.02–2.73
2.32**
1.26–4.28
Vomiting
3.19***
2.04–4.98
3.35***
2.19–5.12
1.96
0.98–3.89
1.63
0.81–3.31
2005 Exercise
1.05
0.82–1.34
0.87
0.68–1.13
1.12
0.89–1.41
0.89
0.68–1.15
Mild dieting
1.41***
1.19–1.66
0.94
0.68–1.31
1.33*
1.06–1.68
1.15
0.86–1.55
Fasting
2.85***
2.35–3.45
2.75***
1.90–3.96
2.81***
1.98–3.99
3.41***
2.11–5.51
Taking diet pills
3.57***
2.57–4.95
2.90***
1.97–4.26
4.08***
2.46–6.79
2.13*
1.16–3.91
Vomiting
3.08***
2.17–4.38
3.84***
2.47–5.98
5.06***
2.80–9.11
4.42***
2.12–9.20
Extreme dieting
2007 Exercise
0.89
0.77–1.04
0.63*
0.41–0.97
1.13
0.93–1.37
0.97
0.73–1.28
Mild dieting
1.09
0.87–1.36
0.74
0.51–1.08
1.18
0.97–1.44
0.90
0.74–1.09
Fasting
3.43***
2.67–4.39
1.93**
1.30–2.86
2.58***
1.73–3.83
2.28**
1.40–3.73
Taking diet pills Vomiting
5.10*** 4.51***
3.66–7.10 3.16–6.45
1.69* 2.53**
1.01–2.82 1.54–4.17
2.95*** 3.27***
1.88–4.61 1.80–5.94
3.15*** 2.63**
1.83–5.41 1.33–5.19
Extreme dieting
The reference group of each weight control behavior is no engagement of each behavior to lose weight or keep from gaining weight in the past 30 days. CI confidence interval; AOR adjusted odds ratio * p \ .05; ** p \ .01; *** p \ .001
might be that adolescents have a belief that smoking helps maintain or reduce body weight. As hypothesized, extreme dieters were more likely to be current smokers among boys and girls, which is extreme dieters who have a stronger desire to lose weight might be more likely to pick up cigarettes when they perceive that nicotine would help reduce body weight. Another plausible explanation for this
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finding is Krahn’s (1991) biological model, where he illustrated that food deprivation increases a desire for nicotine, alcohol, and drugs. Therefore, a feeling of deprivation among dieters might stimulate an urge to smoke cigarettes. This feeling of deprivation might be stronger among extreme dieters than mild dieters, which leads to the differential likelihood of smoking.
J Youth Adolescence (2009) 38:1364–1373
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Fig. 1 Trend in current smoking by extreme dieting status among US adolescents, 1999–2007 Youth Risk Behavior Survey (N = 71,854). Note: the vertical line indicates 95% confidence interval
Trends in the association between smoking and extreme dieting are also troublesome. Whereas some of the three extreme dieting behaviors were not associated with current smoking in the years 1999–2003, all of the extreme dieting behaviors were associated with adolescents’ current smoking from 2005 on regardless of gender and weight status. This may indicate that the belief in the link between smoking and weight control is becoming more pervasive. This suggests a need for aggressive intervention to curb the misperception about smoking as a weight control strategy among adolescents, especially among those who engage in extreme dieting. Among the three modes of extreme dieting, fasting was an independent predictor of smoking consistently across all years. This might be due to higher statistical power coming from more adolescents reporting fasting than the other two extreme dieting behaviors. This also might be explained by the food deprivation induced by smoking (Krahn 1991). Fasting may result in a stronger feeling of food deprivation than taking pills or vomiting because fasting cannot satisfy the appetite, whereas the latter two behaviors do. Therefore, among the three modes of extreme dieting behaviors, fasting is more likely to induce substance use, such as tobacco smoking, according to the biological model (Krahn 1991). This warrants future research to investigate the mechanisms by which adolescents who engage in different
modes of extreme dieting show different levels of smoking behavior. Another notable finding is that extreme dieters showed a higher variability of current smoking rate than non-extreme dieters. This indicates that extreme dieters are more heterogeneous in smoking behavior, which suggests that interventions against adolescent smoking among extreme dieters need to be more varied than among non-extreme dieters. With regard to this, a result deserving mention is that the gap in the smoking rates between extreme dieters and non-extreme dieters was consistent across all the years among non-overweight girls. This temporal stability might reflect the stubborn nature of smoking behavior in this group. Even when the gap decreased in all the other three groups from 2005 to 2007, it did not for non-overweight girls. Although further investigation using data from future years is needed for corroboration, this finding alludes to the possibility that it would be more difficult to implement smoking cessation intervention for female extreme dieters than for other groups. The current study confirms an overall downward trend in current smoking among US adolescents, supporting the smoking epidemic model of Lopez et al. (1994). However, it is noteworthy that smoking rates among overweight boys did not decrease since 2003. Actually, the smoking rate increased between 2003 and 2005 among overweight boys.
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In addition, the prevalence of mild dieting among overweight boys increased over the years whereas it remained unchanged or decreased among other adolescent subgroups. Taken together, these findings suggest that weight concerns are increasing among boys and that an increasing proportion of overweight boys might start smoking to lose weight or to keep from gaining weight. Thus, more targeted interventions with tailored messages are needed for overweight boys. Findings of this study have the following limitations. Self-reported weight and height measures were used to compute weight categories, which might have skewed findings. However, according to Goodman et al. (2000), a very high correlation exists between self-reported and measured weight and height measures among adolescents. Adolescents may have also underreported their smoking and unhealthy dieting behaviors due to their own social concerns. The YRBS data collection protocol did ensure the anonymity and confidentiality of the survey responses, which may have combatted this. Another limitation may be that the data used in this study was collected in schools. Findings may not be generalized to out-of-school adolescents and truants. Interpretations of the findings should be made in light of these limitations. Despite the above limitations, this study does contribute to the literature on adolescent development. This is the first study to examine trends in the association between smoking and weight control behaviors using multiple years of data from nationally representative samples of US high school students. It provides much insight into the association between smoking and weight control behaviors, particularly on the heterogeneity in smoking behavior between adolescents with different modes of weight control behaviors (mild dieting vs. extreme dieting and fasting vs. taking diet pills or vomiting). Additionally, this study provides valuable information on recent trends in the magnitude of the association between current smoking and weight control behaviors among four different groups formed by gender and weight status. Adolescents who engage in extreme dieting are more likely to be current smokers and this group of adolescents need increased attention and care from health professionals. Conflicts of interest statement no conflict of interest.
The authors declare that they have
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Author Biographies Dong-Chul Seo is professor of applied health science and statistical consultant to faculty in his School at Indiana University. He received his Ph.D. in health behavior from Indiana University and has more than 20 years’ experience in public health and expertise in program evaluation and biostatistics. His primary research centers on addictive/risky behavior such as tobacco and alcohol use. He directs Tobacco Control and Wellness Research Working Group. Nan Jiang is a Ph.D. candidate in health behavior at Indiana University. She is originally from China and a graduate of Peking Union Medical College. She has work experience with UNICEF China Office, Peking Union Medical College Blood Disease Hospital in China, and Indiana State Department of Health in Indianapolis. Her research focuses on tobacco prevention and cessation especially among adolescents.
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