Monetary values of changes in Body Mass Index: do spouses play a role?

The public-health challenges associated with increased body weight have long been stressed, but greater attention has lately been brought to how individuals are affected psychologically. This can be rooted in factors such as social norms and interpersonal relationships, including marriage or cohabitation. We estimate the “utility-maximizing” Body Mass Index (BMI) and calculate the implied monetary value of changes in BMI for individuals and their spouses using the compensating income variation method and data from the Household, Income, and Labour Dynamics in Australia Survey. Random-effects models are estimated for women and men separately and windfall income is used to address the endogeneity of income. While the spousal analysis suggests that couples generally dislike having substantially different BMI levels, women most strongly dislike having a higher BMI than their spouses and men have the highest dislike when their BMI is lower than their spouses. On average women prefer to be 4.8 BMI points below their spouses while men prefer to be 2.5 BMI points above their spouses. Similarities and differences in lifestyle are explored in this context. Results also suggest that the optimal own BMI is 28.0 and 25.1 for men and women, respectively. The annual value of reaching optimal weight ranges from $13,483 for women with underweight to $26,647 for women with obesity. Men on the other hand place greater value on not being with underweight ($29,064) than being with obesity ($14,405). The results highlight important gender differences and relative effects based on spousal BMI.