To our knowledge, this work is among the first in the United States to include type of disability as a variable in describing the demographic characteristics of US adults by BMI. Our findings show that more than 40% of obese adults in our sample had at least 1 disability.
Excluding underweight respondents, disability prevalence increased among respondents as their BMI increased. Although this was noted for most types of disability, it was highest among those reporting a movement difficulty. Our finding that movement difficulty was substantially higher among those who are obese compared to those of normal weight is consistent with prior research that found that people who were obese were more likely than people of a normal weight to have a functional impairment (16
) and to have an increased risk of ADL limitation (17
). Movement difficulty may hinder physical activity, preventing people with disabilities from meeting the physical activity guidelines for adults with disabilities; this is problematic because engaging in physical activity is an aspect of weight loss or weight maintenance (18
). The prevalence of visual limitation also increased as BMI increased. Some studies have linked obesity with certain eye disorders, although empirical evidence is mixed (19
). However, visual difficulty may limit the ability to navigate environment, and adults with visual impairments report more difficulty with physical activity (20
Obese adults also reported higher prevalence of social and work limitation compared with those of a normal weight. This limitation in work is consistent with prior research (21
) that demonstrated that younger and middle-aged obese workers had a reported prevalence of work limitation similar to that of middle-aged and older-aged workers, respectively, who were not overweight or obese. Our study shows that the prevalence of work limitation increased 2.8 percentage points for obese men compared with normal-weight men (11.3% vs 14.1%) and 9.3 percentage points for obese women compared with normal-weight women (8.9% vs 18.2%). The reason behind the sex difference is unclear and a possible direction for future work.
We found a higher prevalence of disability among underweight men than among obese men. However, underweight women had a lower prevalence of disability than obese women. Among obesity categories by disability type, the prevalence of disability followed a reverse J
- or U
-shaped distribution for men and a J
-shaped distribution for women. A J
- or U
-shaped distribution has been noted in work comparing BMI with death (22
) and illness (23
). The finding that people who are underweight have a higher prevalence of disability may not be unusual because people who are underweight are more likely than people who are overweight to report moderate to heavy levels of cigarette smoking (23
), a leading cause of illness and death (24
). Furthermore, being underweight has been associated with early mortality among people with cognitive impairments (25
), and illness may cause a person to become underweight or to develop a disability.
We note several additional limitations to our analysis. First, our findings likely underestimate disability among people who are obese. That is, BMI may underestimate obesity (26
) for people with certain disabilities related to differences in body composition, such as spinal cord injury (26
) and limb loss (27
). Alternative measures, such as measuring arm circumference (28
), may be more appropriate for defining obesity in people with certain disabilities. Second, BMI measures in the NHIS are based on self-reported height and weight, which may underestimate obesity prevalence because of a possible reporting bias (29
). Third, the results may be sensitive to the definition of disability used. That is, the disability definition used here is detailed, inclusive, and consistent with the definition used by ADA (10
); thus, we believe that it is appropriate for public health purposes. However, if others were to use a more limited measure of disability, the findings may differ (eg, a measure of disability linked solely to the ability to work) (2
). Fourth, we did not use the NHIS imputed income files to assess prevalence of adults in each household income category. Fifth, the NHIS does not survey institutionalized adults or those on active military duty; therefore, we may have underestimated the true prevalence of disability. Thus, our results cannot be generalized to these populations. Finally, obesity has been identified as a leading secondary condition experienced by people with a disability (6
); also obesity may lead to disability. Addressing the issue of causality (ie, which came first, the obesity or the disability) requires information on the duration of obesity and disability. However, historical data on disability duration are largely unavailable. To reduce issues pertaining to causality, we excluded approximately 5% of respondents who reported weight as the cause of their disability. By re-estimating the data, we found our results were robust (ie, similar to those shown in and ).
This research contributes to the literature on obesity prevalence by including disability as a demographic characteristic and considering type of disability in assessing the burden of obesity in a nationally representative US sample. People with disabilities comprise approximately 26.7% of the normal-weight adult population and 41.0% of obese adults. Knowing that a large percentage of people with obesity have a disability, and knowing the type of disability, will assist public health workers in designing interventions to reduce obesity that include people with disabilities. The systematic collection, analysis, and interpretation of surveillance data are essential to the planning, implementation, and evaluation of effective public health programs. Routine inclusion of disability as a variable in public health surveillance will inform and strengthen the planning and implementation of public health programs.