The fattening speed: understanding the impact of internet speed on obesity, and the mediating role of sedentary behaviour

We examine the impact of access to high-speed internet on obesity. Using 14 waves of longitudinal data from the Household, Income and Labour Dynamics in Australia (HILDA) survey and a newly constructed dataset on the rollout and adoption rate of the National Broadband Network (NBN) across Australian postcodes, we find that access to high-speed internet has a positive effect on obesity. Specifically, our preferred instrumental variable estimates, which predict the variation in timing and location of internet access upgrades, suggest that a 1 % increase in the proportion of a postcode that has access to NBN is associated with a 1.573 increase in Body Mass Index and a 6.6 percentage point increase in the probability of being obese. These results are robust to several checks and alternative specifications. We also find that sedentary behaviour and inactivity are mechanisms through which access to high-speed internet transmits to obesity.