Though several randomized controlled trials have investigated the effects of ultraprocessed foods (UPF) on obesity, leading to news coverage that suggests ultraprocessing is inherently harmful, the reality is different, according to the authors of this Perspective. Based on the design of clinical trials conducted to date, it is very difficult to attribute negative effects observed in trial participants to ultraprocessing. Instead, these effects are likely due to differences in traditional nutritional properties that UPFs frequently exhibit – including soft textures (which can lead people to eat more and faster), high calorie density, high amounts of saturated fat and salt, and low fiber and protein content. These properties affect health regardless of the extent of food processing, Faidon Magkos and colleagues say. The authors describe the five clinical trials conducted so far on UPFs in the USA, UK, Denmark, and Japan, outlining the trials’ methods, variable findings, and limitations. “Collectively, available randomized controlled trials provide weak support for an ultraprocessing-specific effect of UPFs on body weight regulation and cardiometabolic function that is independent of established nutritional determinants,” Magkos et al. write. They note that the UPF concept encompasses many foods that are unhealthy, but also foods that are not necessarily harmful and even some that are beneficial. Based on evidence from the trials, they recommend that policy guidance around UPFs should focus on distinguishing nutritionally poor, calorie-dense, and rapidly consumed foods – regardless of their degree of processing.

 

Podcast: A segment of Science's weekly podcast with Faidon Magkos, related to this research, will be available on the Science.org podcast landing page after the embargo lifts. Reporters are free to make use of the segments for broadcast purposes and/or quote from them – with appropriate attribution (i.e., cite "Science podcast"). Please note that the file itself should not be posted to any other Web site.

After more than a decade of steady decreases, surface ozone (O₃) trends in North America reversed in 2015 despite policy mitigation efforts, report Weizhi Deng and colleagues. Their research links this reversal to O₃ emissions from wildfires and additionally documents a related rise in premature mortality. “Despite regulated reductions in anthropogenic emissions of O₃ precursors, observation stations indicate that policy-relevant surface O₃ levels have plateaued,” the authors write, tying this phenomenon to an increase in wildfire emissions. They describe the relationship between wildfires and surface O₃ trends more closely by using deep learning models to evaluate existing yet sparse EPA, satellite, and meteorological measurements, generating a dataset of daily surface O₃ measurements at a 1-kilometer resolution in North America from 2003 to 2024. Doing so revealed that O₃ trends flipped from a decrease of 0.65 parts per billion (ppb) per year before 2015 to an increase of 0.13 ppb per year after 2015. Further analyses determined this post-2015 rate would have stayed in decline (−0.25 ppb per year) if not for wildfire emissions. The authors then examined correlations between O₃ trends and premature deaths, attributing emissions to an additional 318 deaths per year since 2013. Essentially, after 2013, the mortality rate attributable to wildfire-sourced O₃ rose by 46%. Finally, Deng et al. examined O₃ emissions from 2022 to 2024, a period marked by extreme fires and smoke in Canada. Results showed wildfire emissions alone exposed 43 million people to unhealthy levels of air pollution, in excess of the United States’ O₃ air quality standard of 70 ppb. The authors suggest that these emissions prevented the United States from tightening its O₃ air quality standard by 4 ppb. They elaborate: “If the O₃ standard were lowered to 65 ppb, 60% of the population (202 million people) would fall into nonattainment, and under a 60-ppb standard, the fraction would increase to 87% (294 million people). These findings demonstrate the challenge in adopting a more stringent O₃ standard as growing wildfires contribute to high O₃ episodes.”

A new study of more than 16,000 people who sought help from a nationwide abortion and miscarriage hotline found demand for confidential clinical support surged both before and after the U.S. Supreme Court decision that overturned federal abortion protections.

States with restrictive abortion policies saw slower growth in the proportion of female medical school applicants following the 2022 reversal of Roe v. Wade, according to a new study published in the open-access journal PLOS Global Public Health by Amrit Kirpalani of Western University, Canada, and colleagues.

A new Dartmouth study maps the interplay of personal choice and social networks that can lead to a phenomenon they call "overarming," where the collective cost of firearm ownership outweighs the individual benefits of possessing a gun. The team developed a model based in evolutionary game theory to characterize how social factors drive individuals' choices to buy a firearm, how these choices influence others' choices, and whether the choices made by all members of society leads to overarming.