Dickerson et al. BMC Public Health 2011, 11:926 http://www.biomedcentral.com/1471-2458/11/926 those in the obese class III BMI classification versus the obese class II BMI classification. Self-reporting as female among the obese class III BMI classification was asso- ciated with nearly 3 additional BMI points. Educational attainment was also significantly related to BMI among the higher BMI classifications; obese class I, obese class II, and obese class III. For every additional year of edu- cation attained among those in the obese class I BMI classification, the effect on BMI was a reduction of a third of a BMI point. Finally, there did not appear to be significant results to report based on participants’ resi- dential rurality. It appeared this variable was of less importance than other socio-demographic variables. Is it time to exercise? A noteworthy finding in this study is the effect moder- ate PA had on BMI among those in the “obese class III” BMI classification, also known as the “morbidly obese”. Part of the challenge in addressing PA for the morbidly obese is overcoming barriers endemic to physical condi- tions of obese individuals. One such barrier is the per- ception of breathlessness associated with exercise [29]. This barrier can prevent obese individuals from begin- ning an exercise regimen. However, there is encouraging evidence that training programs incorporating respira- tory muscle development can be successful in helping obese individuals reach their PA goals, improve their metabolic health, and sustain their level of exercise [29]. In addition, mobility limitations of obese individuals caused by diseases such as osteoarthritis and joint pain, must be taken into account when planning appropriate PA programs [30]. Another barrier to PA is motivation, particularly because obese individuals often report a lack of energy or feeling too tired to exercise [31]. These are all unique barriers to PA that programs must recognize in order to be successful. Targeted interventions are needed In addition to indicating the heterogeneous effect of sedentary behaviors among BMI classifications, our study also highlights the role of socio-demographic fac- tors among the various degrees of obesity. While the coefficients in our study identified the unique effect of each independent variable on BMI, the results indicate future research could benefit by examining interaction effects of sedentary and lifestyle behaviors with select demographic groups such as Hispanics and African- Americans. Such analysis could be a powerful comple- ment to the broader findings of our study, and likely highlight the need to tailor interventions not only toward individual BMI classifications, but also toward the multi-cultural composition of those classifications. Addressing the unique needs of the Hispanic [32] and African-American populations [33] can improve the Page 9 of 10 chances of developing programs that successfully improve the health of these populations. Limitations Our study used a unique statistical method to analyze the homogeneity of effect between sedentary behaviors, socio-demographics, and BMI classification. However, simultaneous quantile regression does not have a true equivalent of the coefficient of determination which makes it difficult to establish how much of the variance in the dependent variable was explained with the model. Further, while chronic diseases were recognized in the selection criteria, individual chronic disease characteris- tics were not analyzed in this study. Future studies would benefit from incorporating individual disease vari- ables as well as individual values of lipoprotein lipase (LPL), low-density lipoprotein cholesterol (LDL-C), blood sugar, and other biometric markers where appro- priate. Finally, the data analyzed in this study was self- reported from several communities in central Texas. As a result, it has limited generalizability. It must also be noted the BVHA solicited households for individual responses to the study instrument. As such, individuals not living in households are likely not well represented in the survey results. Conclusion This study found the association of PA and sedentary behavior with BMI is not homogenous across BMI clas- sifications. In fact, PA and sedentary behavior appear to become more important to those who are obese to mor- bidly obese. This indicates public health efforts must dif- ferentiate interventions for individuals of different BMI classifications. While the association between these vari- ables and BMI is well accepted in the literature, this study identifies the degree to which these aspects of life matter to BMI management among those of varying BMI classifications. Acknowledgements We recognize support from The Center for Community Health Development which is a member of the Prevention Research Centers Program, supported by the Centers for Disease Control and Prevention cooperative agreement number 5U48DP000045. Author details 1Department of Health Policy & Management, School of Rural Public Health, Texas A&M Health Science Center, College Station, Texas, USA. 2Department of Health Promotion & Behavior, College of Public Health, The University of Georgia, Athens, Georgia, USA. 3Department of Environmental & Occupational Health, School of Rural Public Health, Texas A&M Health Science Center, College Station, Texas, USA. 4Department of Social & Behavioral Health, School of Rural Public Health, Texas A&M Health Science Center, College Station, Texas, USA. Authors’ contributions JD conceived of the study and conducted the background research, descriptive statistics, and the simultaneous quantile regression modeling. MS