As access to high-speed internet grows, so does the risk of obesity, with new findings highlighting how faster internet contributes to more sedentary habits and physical inactivity, increasing BMI and the probability of obesity.
Study: The fattening speed: Understanding the impact of internet speed on obesity, and the mediating role of sedentary behaviour. Image Credit: Miguel AF / Shutterstock
In a recent study published in the journal Economics & Human Biology, researchers in Australia investigated the impact of high-speed internet access on obesity, focusing on the mediating role of sedentary behavior and inactivity.
Background
Obesity is a critical public health issue worldwide, with increasing prevalence in developed nations. In Australia, nearly two-thirds of adults are overweight or obese, contributing to a significant economic burden of over AU$ 87 billion annually. Obesity is closely linked to an elevated risk of cardiovascular disease, diabetes, stroke, and certain cancers. While many factors contribute to obesity, including diet and genetics, further research into the role of modern lifestyle factors, such as internet usage, is increasingly relevant.
About the study
The present study examines the impact of internet speed on obesity by using Body Mass Index (BMI) and a binary indicator of obesity as dependent variables. The primary independent variable is the share of each postcode with access to the National Broadband Network (NBN), controlling for individual characteristics with fixed effects and clustering standard errors at the postcode level. The study utilized 14 waves of data from the Household, Income and Labour Dynamics in Australia (HILDA) survey, covering the period from 2006 to 2019. Baseline results are estimated using ordinary least squares (OLS) regressions.
To address potential endogeneity, such as individuals with sedentary tendencies moving to areas with faster internet or regions with high obesity rates demanding better internet, a two-stage least squares (2SLS) approach is employed. The timing of NBN installation varies by postcode and serves as an instrument. This instrument is considered valid as it correlates with internet access but not directly with obesity, and evidence shows the NBN rollout was primarily based on technical feasibility rather than socioeconomic conditions. A binary variable for remoteness controls for geographic differences.
A staggered difference-in-differences (DID) design further ensures robustness, testing the no anticipation effect to confirm that behavior did not change before internet access. Lastly, sedentary behavior and physical activity are analyzed as mechanisms, examining whether they mediate the relationship between internet speed and obesity.
Study results
The results show a positive relationship between access to faster internet and obesity. In the baseline results, a 1% increase in the proportion of a postcode with access to the NBN is associated with a 0.635 increase in BMI and a 2.8 percentage point increase in the probability of being obese. These findings align with previous research in developed countries but differ from studies focusing on developing countries, like China, where internet diffusion is at an earlier stage. The differences in economic and internet development stages likely explain the variations in results between Australia and countries like China.
Covariate analysis reveals that age has an inverted U-shaped relationship with obesity, while factors like widowhood reduce the likelihood of obesity. Interestingly, higher income, employment, and education levels are associated with an increased risk of obesity, while long-term illness or disability further elevates the likelihood. The endogeneity-corrected estimates, obtained through a 2SLS approach, suggest that baseline estimates understate the true effect. After correcting for endogeneity, a 1% increase in NBN access corresponds to a 1.574 increase in BMI and a 6.6 percentage point rise in obesity probability.
Further analysis demonstrates that sedentary behavior and physical inactivity mediate the relationship between internet speed and obesity. Internet access is linked to a decrease in metabolic equivalent of task (MET) minutes (time spent on activities that enhance metabolism) and an increase in physical inactivity and sedentary behavior. Including MET minutes, inactivity, and sedentary behavior in the model reduces the magnitude of the effect of internet speed on obesity, confirming them as key mechanisms.
Subgroup analyses show that the impact of internet speed on obesity is more substantial for men than women and more pronounced among young adults compared to middle-aged and older adults. The findings also reveal that high-speed internet is more strongly associated with lower-risk obesity (Class 1), with similar trends observed for overweight and underweight categories. Robustness checks, including clustering at both the postcode and individual levels, confirm the consistency of the results. Finally, a DID design further reinforces the positive relationship between high-speed internet access and obesity, validating the study's findings across multiple methodologies.
Conclusions
In summary, the findings show that increased access to the NBN is linked to higher BMI and a greater likelihood of obesity. The effects of internet access on obesity are more significant than many individual-level factors, such as income, marital status, and employment. Sedentary behavior and physical inactivity are key mechanisms linking internet speed to obesity. These results suggest that policies encouraging physical activity and reducing sedentary behavior are crucial to addressing the public health implications of high-speed internet access.