Abstract
Internet use is often regarded as a double-edged sword; while it offers access to new activities and information, it may also crowd out other beneficial activities because of time constraints. This paper investigates the effect of Internet use on health, with a particular focus on body weight, which is measured by the incidence of being overweight. The Internet condition in China has undergone tremendous development, providing an ideal context to evaluate the impact of Internet use. Utilizing individual panel data, we employ a fixed-effects instrument variable (FE-IV) strategy using the number of broadband access ports per capita as the instrument. The results show that Internet use significantly increases the probability of being overweight. The effect is more salient among males, younger generations, individuals with lower levels of education, and in the northern region. Further mechanism analysis suggests that Internet use is associated with reduced sleep quality and changes in other health-related behaviors in mixed ways, including greater junk food intake and more exercise. Our back-of-envelope calculations show that Internet-induced overweight may generate substantial medical costs. These findings reveal a hidden health cost of Internet use and call for greater public attention.
Notes
According to the WHO classification, a BMI > = 25 can be further classified as overweight (25–29.9) or obesity (> = 30.0). Here, the term “overweight” refers to the combined category of overweight and obesity, and this definition is consistently applied in the main analysis.
The prevalence of overweight reported by the WHO may be underestimated. According to the Chinese National Health Commission, the overweight rate was 29% in 2002 and 50.7% in 2021, whereas the corresponding WHO figures were 20.77% and 37.96%, respectively.
Overweight and obesity are treated as a single category given that the proportion of obesity in the sample is relatively low (2.36%).
See the official government document at the state council’s website: http://www.gov.cn/zwgk/2013-08/17/content_2468348.htm [in Chinese].
U.S Department of Health & Human Services says screen time at home should be limited to 2 h or less a day. (https://www.nhlbi.nih.gov/health/educational/wecan/reduce-screen-time/index.htm Similarly, American Heart Association recommend that teenagers get no more than 1 to 2 h of screen time (https://www.heart.org/en/healthy-living/fitness/getting-active/limit-screen-time-and-get-your-kids-and-the-whole-family-moving
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Acknowledgements
We deeply thank Filiz Garip, Noreen Goldman, Shiko Maruyama, Takeshi Murooka, Fumio Ohtake, Boriana Pratt, James Raymo, Yu Xie, scholars and participants in the OPR/READI Seminar, Princeton University; OSIPP Lunchtime Seminar, Osaka University; 3rd Asian Workshop on Econometrics and Health Economics for helpful comments. All remaining errors are our own.
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The first author received a grant from JSPS KAKENHI, Grant Number 20H05632, for this research.
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Kohara, M., Shen, Y. The cost of Internet use: An examination of the causal impact on body weight. J Evol Econ 36, 64 (2026). https://doi.org/10.1007/s00191-026-00983-4
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DOI: https://doi.org/10.1007/s00191-026-00983-4