Changes in Body Mass Index (BMI) during adolescence play an important role in the association between air pollution exposure and insulin resistance, according to a new study led by USC investigators. The study,  published in JAMA Network Open, found that children who were exposed to higher levels of traffic-related air pollution—specifically nitrogen oxides—tended to have a higher BMI by age 13, and experienced rapid weight gain from adolescence to young adulthood. This, in turn, was linked to higher levels of insulin resistance in their mid-20s. Researchers estimated that 42% of the relationship between early pollution exposure and insulin resistance can be explained by accelerated BMI growth trajectories—which describes how an individual’s BMI changes over time—and further contributes to insulin resistance, a key risk factor for type 2 diabetes. The study included data from Meta-Air2, an ongoing substudy of the Southern California’s Children’s Health Study (CHS) and featured 282 participants enrolled in kindergarten or first grade in 2003, who were actively followed up until 2014. The study’s researchers initiated a follow-up study in 2023 where participants, now young adults, provided blood samples for metabolic biomarker testing.

For the first time, researchers at the National Institutes of Health (NIH) identified patterns of metabolites in blood and urine that can be used as an objective measure of an individual’s consumption of energy from ultra-processed foods. Metabolites are left after the body converts food into energy, a process known as metabolism. Scientists used these data to develop a score based on multiple metabolites, known as a poly-metabolite score, that has the potential to reduce the reliance on, or complement the use of, self-reported dietary data in large population studies. The findings appeared May 20, 2025, in PLOS Medicine.