We use life satisfaction and Body Mass Index (BMI) information from three waves of the SOEP to test for social interactions in BMI between spouses. Social interactions require that the cross-partial effect of partner's weight and own weight in the utility function be positive. Using life satisfaction as a utility proxy, semi-parametric regressions show that the correlation between satisfaction and own BMI is initially positive, but turns negative after some threshold. Critically, this latter threshold increases with partner's BMI when the individual is overweight. The negative well-being impact of own BMI is thus lower when the individual's partner is heavier, which is consistent with social contagion effects in weight. However, this cross-partial effect becomes insignificant in instrumental variable regressions, suggesting that the uninstrumented relationship reflects selection on the marriage market or omitted variables, rather than social interactions.
Keywords: Obesity, subjective well-being, BMI, social interactions
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