While many Americans reported losing weight between 2008 and 2009, the actual prevalence of obesity in the United States increased over this time period, according to researchers at IHME. Results from the study “In denial: misperceptions of weight change among adults in the United States” show that public health officials should interpret self-reported weight losses with caution.

Research objective

Because obesity is related to a wide array of health problems, Americans are encouraged to lose weight to reduce their risk for premature death or chronic conditions such as heart disease and diabetes. While many Americans attempt to lose weight and report weight losses, obesity remains a major health problem, and the prevalence of obesity continues to increase. The authors designed this study to estimate changes in body weight and obesity prevalence among adults in the US over a one-year period and compare these findings to self-reported changes in body weight.

Research findings

Overall, the prevalence of obesity increased from 26% to 26.5% between 2008 and 2009. However, Americans tended to report weight losses over this same time period. The obesity prevalence among men increased by 0.3% between 2008 and 2009, despite reports of weight loss that, if realized, would have resulted in a decline in prevalence of 2%. Among women, obesity prevalence increased 0.5% between 2008 and 2009, despite reported weight losses that would have translated to a decline of 0.9%. Therefore, self-reported changes in body weight corresponded to a 2.3 percentage point underestimation of the observed increase in obesity prevalence among men, and a 1.4 percentage point underestimation of the observed increase in obesity prevalence among women.

The authors found that the odds of self-reported weight gain were substantially higher for men and women under the age of 40, those identifying as black, Native American, or Hispanic, current and former smokers, those consuming less than five servings of fruits and vegetables per day, those reporting no physical activity, those with diagnosed chronic diseases, frequent poor mental health, and insufficient sleep, and those lacking health care coverage.

Analytical approach

Data from the 2008 and 2009 Behavioral Risk Factor Surveillance System (BRFSS) were used. The BRFSS, a yearly cross-sectional survey of adults in the US designed to monitor leading risk factors for morbidity and mortality at the local, state, and national levels, asks participants to report their weight and height at the time of the interview, as well as their weight one year prior to the interview. Respondents reporting different body weights at the two time points were asked if the change was intentional or unintentional. Demographic factors and health behaviors such as smoking and physical activity are also assessed. This study includes data from 385,416 survey participants in 2008 and 394,700 participants in 2009.

The authors estimated current average body weight and prevalence of obesity in 2008 and 2009 and prior average body weight and prevalence of obesity in 2008 (using data from the 2009 BRFSS) to determine the discrepancy between the calculated and reported changes in weight and obesity prevalence.

Policy implications

These results show that while many Americans are saying they are losing weight over time, routine surveillance data indicate that, on average, they are actually gaining weight. The authors note that public health and medical professionals should interpret self-reported weight changes with caution when developing, implementing, and evaluating programs designed to prevent and control weight gain. In addition, since it appears that many Americans are not accepting the reality of their weight gain and in fact believe that they are losing weight, they may not be motivated to engage in behaviors leading to healthy weight goals. Increased efforts are needed to help individuals and communities achieve these goals.


Wetmore CM, Mokdad AH. In denial: misperceptions of weight change among adults in the United States. Preventive Medicine. 2012; 55(2):93-100.