BMJ  2006;333:25-26 (1 July), doi:10.1136/bmj.38840.608704.80 (published 12 May 2006)

Research

Smoking, obesity, and their co-occurrence in the United States: cross sectional analysis

¹ Columbia University, Mailman School of Public Health, New York, NY, USA, ² American Legacy Foundation, Washington, DC 20036, USA

Abstract

Objectives To describe the prevalence of obesity, smoking, and both health risk factors together among adults in the United States.

Design Cross sectional analysis of a national health interview survey.

Setting United States.

Participants 29 305 adults (aged 18) in 2002.

Main outcome measures Prevalence of adults who are obese (body mass index 30), who smoke, and who are obese and smoke. Prevalence was stratified by age, sex, ethnic group, education, and income.

Results 23.5% of adults were obese, 22.7% smoked, and 4.7% smoked and were obese.

Conclusions Although the proportion of adults who smoke and are obese is relatively low, this subgroup is concentrated among lower socioeconomic groups.

Introduction

Obesity and cigarette smoking are primary risk factors for several chronic conditions and early death in a large number of people in the United States. The prevalence of smoking among adults is 22.5% (45.8 million people).¹ The proportion of obese adults is also high—about 31% of adults have a body mass index of 30 or more.² Although smoking and obesity are public health priorities in the US,³ the overlap between the two conditions has not been measured at population level. Because the presence of these two conditions together probably carries an increased risk to health, statistics on how these conditions overlap could help in the development of an effective policy for prevention and treatment.

Methods

We used data from the 2002 national health interview survey (NHIS) to conduct a cross sectional analysis of 29 305 adults ( 18 years) and estimate the proportion of adults in the US who smoke and are obese. Prevalence was stratified by various sociodemographic factors. Rubin's multiple imputation procedure was used to replace missing values of family income. We analysed all data with Stata software, version 8 and adjusted the results with sampling weights to derive population estimates from the survey sample.

Results

Nearly 41.5% of adults (81 million aged 18 years) in the US are obese or smoke, and about 4.7% (9 million) smoke and are obese (table). Overall, 5.3% of men and 4.2% of women smoke and are obese. This proportion is higher in African Americans (7.0%) than in other racial or ethnic groups. A greater proportion of people with lower income and education levels smoke and are obese. With the exception of the over 65 age group, in which the prevalence of both conditions is low (1.1%; probably because these risk factors are associated with early death), little variation occurs across age groups.

View this table: [in this window] [in a new window]   Prevalence of obesity, smoking, and both risk factors among adults (18 years): US National Health Interview Survey, 2002. Values are percentages (95% confidence intervals)

 

Discussion

Although the proportion of adults who smoke and are obese in the US is relatively low (4.7%), the total number is 9 million. Each condition carries an independent health risk, and the presence of both conditions may have increased risks, but little is known about the best treatment for people who smoke and are obese.^{4 5} Average weight gains of 2.8 to 4.4 kg for men and 3.8 to 5.0 kg for women occur when people stop smoking,^{6 7} but a high proportion of people who stop smoking have large and persistent weight gain. The benefits of stopping smoking are thought to outweigh the risk of weight gain in the overall population,⁶ but the effects on people who are obese are unclear. It is not known whether people who smoke and are obese are less, more, or equally likely to gain weight than people who are not obese. Conversely, it is not known how restricting dietary intake affects attempts to stop smoking and relapse among obese people. Currently, most programmes for stopping smoking do not encourage simultaneous attempts at weight control because interventions aimed at changing several health behaviours have not been very successful.⁸

Treatments for people who smoke and who are obese need to be investigated. Clinical trials should monitor the effects of programmes aimed at simultaneously stopping smoking and weight control to document and respond to any unintended consequences. These results could be used to develop protocols for the optimal clinical management of this population.

What is already known on this topic Smoking and obesity are two of the leading causes of mortality and morbidity in the United States Lower socioeconomic groups are disproportionately affected by smoking and obesity What this study adds The overlap of smoking and obesity among adults in the US is low (4.7%), but the total number of people affected is 9 million, and this subgroup is concentrated among lower socioeconomic groups Statistics on the overlap of these two conditions could help inform clinical interventions

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This article was posted on bmj.com on 12 May 2006: http://bmj.com/cgi/doi/10.1136/bmj.38840.608704.80

Contributors: CGH conceived and designed the study and helped prepare the final draft. DV directed the data analysis and helped prepare the final draft. KLM helped interpret the data and prepared the original draft manuscript. MPG helped interpret the data and prepare the final draft. HX conducted the analyses and helped prepare the original draft manuscript.

Funding: American Legacy Foundation.

Competing interests: None declared.

References

1. Centers for Disease Control and Prevention (CDC). Cigarette smoking among adults—United States, 2002. MMWR Morb Mortal Wkly Rep 2004;53: 427-31.[Medline]
2. Hedley AA, Ogden CL, Johnson CL, Carroll MD, Curtin LR, Flegal KM. Prevalence of overweight and obesity among US children, adolescents, and adults, 1999-2002. JAMA 2004;291: 2847-50.[Abstract/Free Full Text]
3. Healthy People 2010. 2nd ed. Washington, DC: US Department of Health and Human Services, 2000. www.healthypeople.gov/document/html/tracking/THP_Intro.htm (accessed 3 May 2006).
4. Greenlund KJ, Zheng ZJ, Keenan N, Giles WH, Casper ML, Mensah GA, et al. Trends in self-reported multiple cardiovascular disease risk factors among adults in the United States, 1991-1999. Arch Intern Med 2004; 164: 181-8.[Abstract/Free Full Text]
5. Marrero JA, Fontana RJ, Fu S, Conjeevaram HS, Su GL, Lok AS. Alcohol, tobacco, and obesity are synergistic risk factors for hepatocellular carcinoma. J Hepatol 2005;42: 218-24.[ISI][Medline]
6. Flegal KM, Troiano R, Ramuk E, Kuczmarski RJ, Campell SM. The influence of smoking cessation on the prevalence of overweight in the United States. N Engl J Med 1995;333: 1165-70.[Abstract/Free Full Text]
7. Williamson DF, Madans J, Anda RF, Kleinman JC, Giovino GA, Byers T. Smoking cessation and severity of weight gain in a national cohort. N Engl J Med 1991;324: 739-45.[Abstract]
8. Copeland AL, Martin PD, Geiselman PJ, Rash CJ, Kendzor DE. Smoking cessation for weight-concerned women: group vs. individually tailored, dietary, and weight-control follow-up sessions. Addict Behav 2006;31: 115-27.[Medline]

(Accepted 29 March 2006)

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