Is Being Underweight as Bad for Your Health as Being Obese? Evidence from the 2012 Behavioral Risk Factor Surveillance System

Background: Although there are indications that being underweight can compromise health status, most studies examine the health effects of obesity. A clearer understanding of the differential health effects of being underweight or obese could provide avenues for targeted, effective interventions.Objectives: The main study question was: Is being underweight as bad for your health as being obese? Related questions are: Relative to individuals with healthy body weights, what is the health status of those who are underweight? Relative to the health status of individuals who are obese, what is the health status of those who are underweight? Method: To address the study questions, we analyzed data from the 2012 Behavioral Risk Factor Surveillance System (BRFSS) of the US Centers for Disease Control and Prevention (CDC). We definedthe following body weight groups: BMI ≤ 18.5 as underweight; healthy body weight as 18.5 ≤ BMI < 25; overweight as 25 < BMI < 30; Class1 obese as 30 ≤ BMI < 35; Class2 obese as 35 ≤ BMI< 40; and Class3 obese as 40 ≤ BMI. We conduct χ² - and t-tests of health status differences across these body weight classes. Applying a health production framework from health economics we conducted a multivariate analysis to examine the effects of body-weight classes on the likelihood of self-assessed good health status.Results: Relative to individuals with healthy body weights, those who were underweight had poorer health, higher probability of poor health and prevalence of diagnosed chronic health conditions. We found significant (p < 0.000) differences in health status, across the four bodyweight classes (underweight, obese classes 1-3). Being underweight has similar negative health effects as being obese.Conclusion: Differences across the four body-weight classes warrant closer examination to determine appropriate interventions. It is also very important to address being underweight and its effects on health.