The Scale Goes Up, the Joy Goes Down? Investigating the Causal Effect of Body Weight on Happiness

Abstract

Overweight and obesity represent significant public health challenges in many contemporary Western societies. In countries such as Germany, the majority of the population is classified as overweight. While being overweight is well-documented as a risk factor for adverse health outcomes, the relationship between overweight status and happiness remains less clear. This study investigates the impact of overweight and obesity on happiness, utilizing large-scale German panel data (N = 8,815) collected across ten survey waves. Employing fixed-effects regression models that account for relevant time-varying confounders—such as age, health, and employment status—I estimate the causal effect of body mass index (BMI) as a measure of overweight on happiness. The results indicate that being overweight, whether BMI is treated as a continuous or categorical variable, does not have a negative impact on happiness. These findings hold across both genders and all age groups. In some models or subgroups, even small positive associations between weight gain and happiness are observed, despite the exclusion of underweight individuals from the analyses. Further validation is provided by a random intercept cross-lagged panel model (RI-CLPM), which corroborates the initial findings and offers additional insights into the temporal dynamics of this relationship.