Weight misperception among overweight and obese populations is of public health and medical significance and may limit the effectiveness of weight loss and obesity prevention efforts. Nearly one-quarter of our representative US sample of overweight and obese adults misperceived their weight status. In this study, overweight and obese individuals who misperceived their weight status were less likely to want to lose weight and having tried to lose weight as compared to overweight and obese individuals who accurately perceived their weight. This effect was apparent among both men and women and among all racial/ethnic groups, but was especially pronounced for Black men and women. Weight misperception was not a significant predictor of dietary behaviors for most subgroups, but was associated with lower total energy intake among Hispanic women. Additionally, men (especially Black men) who misperceived their weight as compared those who accurately perceived their weight were less likely to be insufficiently active compared to being sedentary and women who misperceived their weight as compared to women who accurately perceived their weight were less likely to meet activity recommendations compared to being sedentary. Importantly, this is the first study, to the best of our knowledge, to have examined weight misperception in relation to a variety of weight-related attitudes and behaviors among a nationally representative sample of overweight and obese men and women in the US.
Findings from our study are largely consistent with the few existing studies in this area. Jones et al., for example, found that adults with class II obesity (BMI = 35.0-39.9) who had inaccurate weight perceptions had less weight concern, less distress regarding overeating, less distress regarding control overeating, less emotional overeating, less eating disinhibition as well as exhibited a nonsignificant trend toward less time spent dieting . Forman et al. found that overweight adults who misperceived themselves as average weight were dieting less often than those who correctly perceived their weight status . In a study of overweight adolescents with type 2 diabetes, Skinner et al. found that those who misperceived their weight had poorer diet such as higher consumption of sugary drinks, eating fast food, having unplanned snacks, and overeating along with low levels of physical activity and more sedentary time . Edwards et al. found that overweight adolescents in the Youth Risk Behavior Survey who accurately perceived their weight were more likely to report trying to lose weight as well as more likely to exercise and consume fewer calories in the past 30 days, but overweight boys who accurately perceived their weight were also less likely to report achieving recommended levels of fruit/vegetable intake and physical activity in the previous week . Taken together, these findings suggest the importance of considering weight perceptions in the design of future behavioral weight loss interventions.
Theories of health behavior provide a useful lens to interpret these findings. Several widely used theories such as the Health Belief Model  suggest that perceived susceptibility to a given condition is necessary to promote healthful behavior change. Consistent with health behavior theory, our findings show that misperceivers are less likely to plan or attempt weight loss, and more likely to overall perform behaviors that increase their likelihood of experiencing weight gain. One notable caveat is our finding that Hispanic women who misperceived their weight status had lower energy intake than those who correctly perceive their weight. However, our overall findings and those of others by and large [28–31] suggest that correcting perception of weight status may be an important consideration in the design of weight loss interventions, particularly those conducted among high-risk subgroups. Intervention efforts are especially needed for overweight and obese men and Black adults, given the groups' high prevalence of weight misperception [4–9, 11, 13, 14, 16–21, 26], their elevated rates of overweight and obesity , and their consistent and strong associations of weight misperception in relation to unhealthful weight-related attitudes and behaviors seen in the present study. We also note that the misperception that should cause the greatest concern is that of extremely obese individuals (almost 50% of our representative sample is obese) for whom, independent of racial/ethnic group, elevated health risks are most certain [48, 49].
Weight misperceptions are potentially modifiable. There are several possible strategies for counteracting misperceptions in the primary care setting and in line with these findings only about 40% of the overweight and obese respondents in our sample reported being told by a physician or health professional that they were overweight. However, when provider counseling occurs, it can be particularly helpful. Several studies have shown that when clinicians advise their obese patients to lose weight, there is an increased likelihood of weight loss attempts [50, 51]. Additionally, the clothing industry might be encouraged to revisit shared clothing sizing standards. The elimination of "vanity sizing" (also known as size inflation, whereby clothing size numbers scale down over time; e.g. a size 14 becomes a size 10)  might reduce weight misperception -- as some individuals monitor their weight with clothing sizes . Marketing campaigns changing societal norms that encourage weight misperception also could be implemented. Such norms exist among men (e.g. overweight men have greater body image satisfaction [19, 54, 55] and men value heavier body weight) [18, 21, 26, 27, 56] and certain racial/ethnic minority groups (e.g. Blacks have greater body image satisfaction independent of their body weight [57–61] and maintain a greater social acceptance of heavier body weight) [61–65]. However, it is important to note that such intervention efforts should be carefully crafted to protect against eating disorders, body image disorders and emotional distress, as these responses may be experienced when weight misperceptions are corrected.
We note that this study also is subject to some limitations. First, many of the gender- and racial/ethnic-stratified models yielded wide confidence intervals and null associations (e.g. all models estimating total energy intake had very wide confidence intervals and we speculate the effect estimates from the energy intake models are unstable); although we maximized the sample size for each analysis for increased power and to avoid any bias by not doing so, lack of power due to smaller sample sizes in these cells might be implicated in the findings. Second, the cross-sectional design of this study does not allow causal conclusions to be drawn. However, despite the well-known limitations of cross-sectional data, our study hypotheses and directionality have intuitive appeal and were based on conclusions from past theoretical and empirical research. Additionally, we relied on self-reported data on health behaviors (i.e. diet and physical activity). Although there can be reliability and validity challenges with self-reported dietary and physical activity measures [66–69] (which may be especially problematic among overweight and obese individuals), this type of data is most commonly used in population-based health research. We report only on leisure-time physical activity, which is only one domain of physical activity behavior and may vary by socio-demographic characteristics, especially race/ethnicity [70, 71]. BMI was used in this study, as is commonly done in population-based research. Nevertheless, previous research has noted that BMI is an imperfect measure of body composition that does not take into account body fat distribution or body fatness (e.g. the ratio of muscle to fat) , which overweight and obese individuals are likely to take into consideration when determining their own weight status  and it may vary by gender and race/ethnicity. The possibility of temporal differences in the time since receipt of diagnosis exists because the medical diagnosis of overweight was not time-delimited (e.g. prior 12 months). Furthermore, as with all observational studies, the possibility of residual confounding cannot be eliminated. However, we adjusted for multiple potential confounding variables in this study. Lastly, Mexicans were largely overrepresented in NHANES and therefore these results might not be generalizeable to other Hispanic subgroups.
The outcomes we selected for this study are reflective of attitudes and behaviors that are necessary for successful weight loss. As such, to enhance the interpretability of our findings, we chose behaviors that are most directly related to weight regulation: total calories and energy expenditure (however other behavioral aspects might be relevant to weight misperception). There is a need for additional research to replicate, extend and contextualize our findings. As the few studies examining weight misperception in relation to weight-related attitudes and behaviors were cross-sectional, longitudinal study designs are needed to establish the temporal ordering of study variables. It is important to note that weight misperception can be examined in multiple ways . In our study, furthermore we do not know what respondents were using as a reference point when reporting weight status. Respondents might have compared themselves with their personal standards of a desired size (which might be based on cultural ideals and/or the size of their family or friends), medical standards of a certain weight for height (e.g. statements from a physician) or some other standard. Finally, in order to correct weight misperception, research is needed to examine causes of weight misperception among overweight and obese individuals (which have yet to be fully elucidated). Social comparison might be an explanation for weight misperception. Research indicates that being exposed to obesity is associated with greater weight misperception (underestimation)  and that increased obesity prevalence rates over the years has been associated with fewer overweight individuals perceiving themselves as overweight [5, 73, 74], increased body weight norms [4, 73], and increased desired and ideal weights [25, 75]. Additionally, we note that weight misperceptions might differ between groups because some experience a weaker BMI-mortality gradient than others (e.g. obesity--until the extreme range--is less lethal for Blacks as compared to Whites) .