Underestimation of Weight Status in Californian Adolescents

Abstract

Background:

Overweight and obese adolescents commonly underestimate their weight status, considering themselves to be at a healthy weight or underweight. These adolescents are more likely to be male, older, and Latino, black, or Native American. Associations with acculturation have not been previously assessed. The goal of this study was to identify the prevalence of underestimation of weight status in Californian adolescents and to identify factors associated with this underestimation, in particular examining relationships with race/ethnicity and acculturation.

Methods:

Secondary data analysis of the 2005 Adolescent California Health Interview Survey.

Results:

A total of 36.6% of overweight and obese Californian adolescents underestimated their weight status. Adolescents not born in the United States had increased odds of underestimating their weight status compared to those born in the United States [adjusted odds ratio (aOR)=1.94, 95% confidence interval (CI) 1.08, 3.49; p=0.03]. No significant associations with race/ethnicity were found. An age–sex interaction was observed with older adolescent males having increased odds compared to younger females.

Conclusions:

Identification of individuals at increased odds of underestimating their weight status may be important in developing and targeting appropriate counseling and interventions to ameliorate long-term health risks of excess weight.

Introduction

Up to 40% of overweight and obese adolescents underestimate their weight status, considering themselves at a healthy weight or underweight.^1–4 These adolescents may not perceive themselves at risk for the long-term negative health outcomes associated with excess weight and, not surprisingly, are less likely to report participating in healthy nutrition and activity habits to maintain or lose weight compared to those with an accurate weight status perception.^1,4,5 This pattern persists into adulthood, with overweight and obese adults who underestimate their weight status, being more likely to disagree that their weight is a health risk⁶ and less likely to report engaging in healthy weight maintenance or weight loss behaviors.^7,8 Some obese adults who underestimate their body size perceive themselves as having a low lifetime risk of developing a myocardial infarction, high blood pressure, diabetes mellitus, or even obesity compared to those with an accurate body size perception.⁹ Accurate perception and awareness of a health condition is an important first step in behavior change,¹⁰ and increased identification of those overweight and obese adolescents most likely to underestimate their weight status can aid health care providers in implementing appropriate counseling and education to support healthy behaviors.

Prior research has found that overweight and obese adolescents who underestimate their weight status are more likely to be male,^1–4,11 older,¹¹ and Latino, black, or American Indian versus white or Asian.^1–4 Little is known as to why some racial/ethnic groups are more likely to underestimate their weight status. One possible explanation for these racial/ethnic group differences is acculturation, a multidimensional process where two cultures influence each other at the individual and group levels, resulting in psychological, sociocultural, and economic adaptation.¹² Acculturation with US culture is positively associated with increased adolescent overweight,^13,14 as well as with lower levels of physical activity and increased fast food consumption.¹⁵ No prior studies have described underestimation of weight status in overweight Californian adolescents, a diverse group characterized by a large immigrant population. The goal of this study was to identify the prevalence of underestimation of weight status in Californian adolescents and to identify factors associated with this underestimation, in particular examining relationships with race/ethnicity and acculturation. We hypothesized that Californian adolescents who underestimate their weight status would be male and older. In addition, Latino adolescents and those who are more acculturated to US culture would have higher odds of underestimating their weight status.

Methods

Analyses used the 2005 Adolescent California Health Interview Survey (CHIS) data from the public release file.¹⁶ Data collection methods have been described previously.¹⁷ In brief, households were surveyed by telephone using random-digit dialing, and a computer–assisted telephone interviewing system was used for data collection. The overall response rate for completed adolescent extended interviews was 14.2%, representing 4029 adolescents. The Stanford University Panel for Medical Research in Human Subjects determined that this research did not require a full review because it involved a secondary analysis of deidentified data.

Measures

Self-reported height and weight were used to determine BMI and sex- and age-adjusted BMI percentiles using growth charts from the CDC.¹⁸ Weight status was categorized as underweight (BMI <5^th percentile), healthy weight (BMI 5^th to <85^th percentile), overweight (85^th to <95^th percentile), and obese (BMI ≥95^th percentile). Weight perception was assessed using the question: “Would you say that you are very underweight, slightly underweight, about the right weight, slightly overweight, or very overweight?” Adolescents were prompted with “Compared to what you would like to be” if needed. Overweight and obese adolescents who perceived themselves as very underweight, slightly underweight, or about the right weight were considered to underestimate their weight status for the purposes of this study.

Race/ethnicity was based on the 2001 former definition of race classification from the California Department of Finance's race categories¹⁹ and recoded into five categories: Latino, white, Asian, African American, and other (the majority of whom reported two or more race/ethnicity categories).

Proxies for acculturation used were language spoken at home (not exclusively English or English only), parental birthplace (one/neither parent US-born or both US-born), and adolescent birthplace (not US-born or US-born).

Statistical Analysis

Analyses were restricted to overweight and obese adolescents. All analyses were weighted to account for sample selection probabilities, potential undercoverage, and nonresponse bias to ensure that the estimates were an unbiased representation of the California population. Additionally, 80 replicate weights and the jackknife method were used to calculate standard errors to account for the complex sampling design of the CHIS. Means and proportions were used to summarize sample characteristics for continuous and categorical measures, respectively. Weighted logistic regression analyses were used to examine the association of race/ethnicity and acculturation proxies with underestimation of weight status in unadjusted analyses as well as after adjusting for age and sex. Two-way interactions were evaluated and retained if significant at p<0.05. The logistic regression analyses are summarized using adjusted odds ratios (aOR) along with their 95% confidence intervals (95% CI). SAS version 9.2 was used for data analysis (SAS Institute, Cary, NC).

Results

A total of 1074 adolescents were overweight or obese, with 52.2% overweight. Mean age was 14.3 years and 59.1% were male. 53.9% were Latino, 28.2% white, 8.8% African American, 5.5% Asian, and 3.6% other (Table 1). A total of 36.6% (n=390) underestimated their weight status, 49.2% reported speaking English only, 89.1% were US-born, and 46.6% had parents both US-born.

Table 1.

Subject Characteristics and Acculturation Proxies Stratified by Underestimation of Weight Status

	Underestimation of Weight Status^b
	All^a		No		Yes
	Wtd Mean (SE)		Wtd Mean (SE)		Wtd Mean (SE)		p value
Age	14.3 (0.1)		14.4 (0.1)		14.1 (0.1)		0.01
	N	Wtd %	N	Wtd %	N	Wtd %
Sex
Female	448	40.9	321	71.6	127	28.4
Male	626	59.1	363	57.8	263	42.2	<0.001
BMI
85 to <95^th %tile	605	52.2	320	49.9	285	50.1
≥95^th %tile	469	47.8	364	78.1	105	21.9	<0.001
Race/ethnicity
White	412	28.2	266	64.2	146	35.8
Latino	464	53.9	293	63.4	171	36.6
Asian	59	5.5	39	74.5	20	25.5	NS
African American	62	8.8	37	53.7	25	46.3
Other	77	3.6	49	64.1	28	35.9
Adolescent birthplace^c
Not US-born	103	10.9	49	50.7	54	49.3
US-born	971	89.1	635	64.9	336	35.1	0.05
Language spoken at home
Not exclusively English	460	50.8	288	65.5	172	34.5
English only	614	49.2	396	61.2	218	38.8	NS
Parent birthplace
One or neither parent US-born	482	53.4	305	65.9	177	34.1
Both parents US-born	592	46.6	379	60.5	213	39.5	NS

Unweighted counts and weighted column percentages (standard error) are shown for the entire sample.

Unweighted counts and weighted row percentages (standard error) are shown for analyses stratified by underestimation of weight status.

Race and adolescent acculturation are confounded in this sample as previously noted.

SE, standard error; Wtd, weighted; NS, not significant.

In bivariate analyses, a greater proportion of males underestimated their weight status compared to females (42.2% vs. 28.4%, p<0.001), and mean age was slightly younger among adolescents who underestimated their weight status (14.1±0.1 vs. 14.4±0.1 years, p=0.01) (Table 1). The prevalence of underestimation of weight status was higher among overweight adolescents compared to those who were obese (p<0.001). Of the acculturation proxy measures, only adolescent birthplace was associated with underestimation of weight status; the prevalence of underestimation of weight status was significantly higher among adolescents who were not US-born compared to US-born adolescents (p=0.05). Underestimation of weight status was not associated with race/ethnicity.

In regression analyses, adolescent birthplace was associated with underestimation of weight status in analyses adjusted for adolescent age and sex. Adolescents who were not born in the United States had nearly twice the odds of underestimating their weight status compared to US-born adolescents (aOR=1.94, 95% CI 1.08, 3.49; p=0.03) (Table 2, model 1). Consistent with the results of the bivariate analyses, the other proxy measures of acculturation were not significantly related to underestimation of weight status. Adolescent race/ethnicity was also not associated with underestimation of weight status after adjusting for adolescent age and sex (Table 2, model 2). Analyses combining underestimation of weight status, race/ethnicity, and acculturation proxies revealed no significant interactions; these were limited to Latinos due to insufficient sample sizes in other racial/ethnic groups. Subgroup analyses of Latino participants (Mexican vs. non-Mexican) showed no significant differences in underestimation of weight status. The two-way interaction between age and sex was significant; as age increased, the odds of males versus females underestimating their weight status also increased (Table 2, model 1). At age 12, males versus females had 1.11-fold increased odds of underestimating their weight status, whereas at age 17, males versus females had 3.55-fold increased odds of underestimating their weight status.

Table 2.

Adjusted Association of Adolescent Race/Ethnicity and Birthplace with Underestimation of Weight Status

	Model 1^a Adjusted OR (95% CI)	Model 2^a Adjusted OR (95% CI)
Adolescent birthplace	p=0.03
US-born	Reference
Not US-born	1.94 (1.08, 3.49)
Adolescent race/ethnicity		NS
White		Reference
Latino		1.06 (0.72, 1.55)
Asian		0.51 (0.21, 1.21)
African American		1.87 (0.94, 3.72)
Other		1.00 (0.45, 2.25)
Age and sex
Males vs. females	p=0.05	p=0.04
Age 12	1.11 (0.62, 1.99)	1.18 (0.66, 2.11)
Age 13	1.40 (0.92, 2.13)	1.50 (0.98, 2.28)
Age 14	1.77 (1.26, 2.49)	1.90 (1.34, 2.70)
Age 15	2.23 (1.48, 3.36)	2.42 (1.59, 3.68)
Age 16	2.82 (1.59, 4.49)	3.07 (1.72, 5.51)
Age 17	3.55 (1.64, 7.69)	3.91 (1.79, 8.55)

Models include the main effects of age and sex.

OR, odds ratio; CI, confidence interval; NS, not significant.

Discussion

This study extends extant knowledge on underestimation of weight status in overweight and obese adolescents by providing a novel examination of associations with acculturation proxies and further describing interactions with sex and age in Californian adolescents. Our findings revealed that a large percentage of overweight and obese Californian adolescents underestimated their weight status, with a majority of these adolescents being overweight, the weight category just above the healthy weight range. All individuals may benefit from appropriate education and counseling on healthy lifestyle behaviors; however, increasing accuracy of weight status perception in overweight and obese adolescents may motivate some individuals to adopt healthy behaviors resulting in weight reduction to the healthy weight range and reduction of the negative health risks associated with excess weight.

Of the acculturation proxies examined, less acculturation as represented by not being US-born was related to increased odds of underestimating weight status. Adolescent birthplace may be associated due to differences in weight emphasis and perception in cultures outside of the United States. However, acculturation level as estimated by language use or parental birthplace was not related to perception of weight status. In one study of overweight Mexican-American adults, those less acculturated based on language preferences were more likely to underestimate their weight status.²⁰ The variability in these findings may be due to differences in the populations surveyed, adolescent versus adult or ethnic group composition. In addition, it is important to note that the examination of three acculturation proxies does not constitute a comprehensive evaluation of the association between acculturation and underestimation of weight status, as acculturation is a complex process involving beliefs and practices that extend far beyond language use and birthplace.¹² Nevertheless, examining language use and birthplace is a starting point in considering the potential role of acculturation in weight perception. Future studies should consider more comprehensive evaluations for acculturation that may include measures of peer group values, media preferences, and body shape and weight ideals.

Our study found no associations between underestimation of weight status and race/ethnicity in contrast to many other studies.^1–4 The absence of a significant relationship may be due to different racial/ethnic mixes in other study samples. This sample is unique in its greater representation of Latino and Asian populations, as well as immigrant populations. Other state and regional samples may be more homogeneous with smaller proportions of immigrant families, whereas samples that attempt to represent the national population are unlikely to accurately reflect Californian adolescents. The 2010 US Census data reveal that California has a higher proportion of Asian persons (13.0%) and persons of Latino origin (37.6%) compared to the nation as a whole (4.8% and 16.3%, respectively).²¹ Additionally, 26.8% of Californians are foreign born compared to 12.4% nationally. Given that our study could not adequately examine more traditionally described non-white subgroups, it is possible that there may be ethnic differences within each broader category of race/ethnicity, percentage of Mexican participants versus non-Mexican participants, for example, that may account for prior associations unobserved in this study.

Associations between underestimation of weight status and either male sex or increased age have been well documented in prior studies.^1–4,11 Our study supports this literature, but it also describes a sex–age interaction not previously noted. In regression analyses, an examination of sex–age interactions showed that older adolescent males have increased odds of underestimating their weight status versus younger males compared to females. One possible explanation of this finding is that BMI is an inadequate measure of adiposity and lean muscle mass. Therefore, males in later adolescence who are muscular with lower body fat may have a higher BMI but may reasonably consider themselves to be at a healthy weight.

Limitations of this study include weight status determined by self-report and not direct measurement, likely underestimating the actual number of individuals who have a BMI >85^th percentile.²² In addition, a limitation of the CHIS dataset is that although 4029 total adolescent responses were available, this represents only 14.2% of those initially contacted. It is unclear how the adolescents who did not complete the survey differed from those in the final sample. Even with over 1000 participants in the final analysis, power remained an issue, with insufficient cell size for complete analyses of African-American adolescents or for clarification of associations by race/ethnicity for adolescents in the other race/ethnicity category. The proxies for acculturation that were available provide a very limited assessment of acculturation. Finally, this is a cross-sectional study and cannot determine causation.

Conclusion

A large percentage of overweight adolescents in California underestimate their weight status and are more likely to be male, older, and not US-born. Overweight and obese adolescents who underestimate their weight status are less likely to report engaging in healthy nutrition and activity behaviors. Therefore, identification of these individuals is vital to providing appropriate counseling and interventions to ameliorate long-term health risks of excess weight in these high-risk individuals. Future studies are needed to further examine the characteristics of adolescents who underestimate their weight status, including possible associations with other measures of acculturation.

Footnotes

Acknowledgments

The project described in this publication was supported by the Lucile Packard Foundation for Children's Health (LPFCH).

Author Disclosure Statement

No competing financial interests exist.

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