In the United States, the prevalence of obesity is expected to rise from 15% at present to almost 26% by 2030, making it a global problem. Although there are many contributing factors to obesity, one of the main behavioural factors is acting without considering the consequences. Impulsivity is associated with ADHD, and that can lead to overeating and unhealthy food choices. Drugs for ADHD frequently help people avoid gaining weight. Researchers used urban scaling laws to examine how changes in urban education, mental health opportunities, food security, and physical exercise affect obesity and ADHD.
The researchers examined data from 19,000 U.S. children and 915 cities to investigate how children’s traits and their living environments influence obesity. The research investigated the connection between impulsivity and obesity by following a three-step approach in cities. Researchers generated scale-adjusted metropolitan indicators (SAMIs) for each city, which quantify how a city’s specific characteristics deviate from what would be expected based solely on its population size. The characteristics examined included adult obesity rates, leisure-time physical inactivity, availability of mental health providers, college graduation rates, food insecurity among children, and the prevalence of ADHD.
Subsequently, they performed a DAG analysis employing the SAMIs. This allowed the team to construct a network model showing potential directional relationships among these urban features. Using this DAG, experts were able to find out what could influence each factor and how ADHD, obesity, and specific environments were related. To ensure their conclusions at the city level were accurate, the researchers analyzed data from a cohort of 19,333 children. The variables found in this dataset were BMI, the severity of ADHD, frequency of physical activity, access to mental health care, the highest level of education in the home, and food affordability. They were interested in knowing if these individual-level relationships mirrored the larger trends seen in cities.
The study investigated how obesity and impulsivity relate to ADHD in different U.S. urban areas, ranging from overall trends to analyzing each individual. First, urban scaling laws were tested on 915 American cities with populations varying from 10,339 to 19,220,403, exploring the following features: people being overweight, kids having ADHD, not being very active during free time, hard access to mental health care, having a college degree, and children not having enough nutritious food. Obesity, ADHD, and inactivity were found to increase at a decreasing rate with city size, with prevalence rates at 0.97 (CI [0.96, 0.98]), 0.98 (CI [0.97, 0.99]), and 0.95 (CI [0.94, 0.96]) respectively, meaning they decreased per capita in larger cities. However, it seems that more mental health providers (exponent 1.17, CI [1.13, 1.21]), more graduates from college (exponent 1.08, CI [1.07, 1.08]), and food insecurity (exponent 1.00, CI [0.99, 1.01]) scale the way we would expect.
More than half of the states experienced marked internal inequities in ADHD, obesity, not being physically active, and education. On the other hand, Hawaii, Vermont, and Maine showed less disparity between groups in these areas. Based on these findings, considering local differences and situations is important when dealing with public health problems such as obesity.
According to the study, having ADHD is strongly linked to obesity in city and individual samples of data. The number of people experiencing obesity, ADHD, and inactivity decreased in large cities, while the number of people receiving mental health care and higher education increased. Food insecurity remained uncertain, but cities in a single state varied a lot. Children with more serious ADHD tend to be less active and record a higher BMI, suggesting that impulsivity raises the risk of being overweight. Based on the findings, helping with mental health, encouraging exercise, and providing more nutritious foods could be useful in reducing the obesity problem in smaller areas. They provide a way to create city-centered strategies in public health.
References: Gan T, Succar R, Macri S, Porfiri M. Investigating the link between impulsivity and obesity through urban scaling laws. PLOS Complex Syst. 2025;2(5):e0000046. doi:10.1371/journal.pcsy.0000046
