Obesity: a disease of the brain?

Kullmann et al. A short-term, high-caloric diet has prolonged effects on brain insulin action in men. Nature Metabolism, February 2025.

Obesity is a growing disease associated with serious illnesses like diabetes, heart disease, and cancer. The World Health Organization has labeled obesity an epidemic, affecting over a billion people worldwide. Obesity is defined by a body mass index (BMI) of 30 or higher, often attributed to poor diet and lack of exercise. However, the underlying biological mechanisms are more complex, particularly regarding the brain’s sensitivity to insulin. A recent study found that even short-term consumption of highly processed foods, such as chocolate bars and potato chips, can significantly alter brain function in healthy individuals, potentially triggering obesity and type 2 diabetes. Normally, insulin suppresses appetite, but in obese individuals, it fails to regulate eating behavior, leading to insulin resistance. The study also revealed that after just five days of high-calorie intake, the brain’s insulin sensitivity in healthy individuals decreased similarly to that observed in obese people. This effect persisted even after returning to a balanced diet for a week. The study involved 29 healthy-weight male participants divided into two groups. One group consumed an additional 1,500 kcal per day from processed snacks for five days, while the control group maintained its regular diet. MRI scans showed increased liver fat in the high-calorie group and a significant reduction in brain insulin sensitivity, which remained even after returning to normal eating habits. Scientists emphasize that the brain’s insulin response adapts to short-term dietary changes before weight gain occurs, highlighting the need for further research into obesity’s neurological factors.

Inheritance of Trauma Through Genes

Mulligan et al. Epigenetic signatures of intergenerational exposure to violence in three generations of Syrian refugees, Scientific Reports, February 2025.

In 1982, the Syrian government carried out a brutal siege in Hama, killing tens of thousands. Beyond the historical and political repercussions, the violence left a hidden impact—one embedded in the genes of Syrian families. A groundbreaking study has now shown that the trauma experienced by pregnant women during the siege has left genetic marks on their grandchildren, supporting the idea that stress and violence can have long-term biological effects. This study explored how trauma is passed across generations through epigenetics, a process in which chemical markers alter gene expression in response to stress. While animal studies have demonstrated the inheritance of stress-induced epigenetic changes, proving it in humans has been challenging. To investigate, researchers studied three generations of Syrian refugees, comparing families who survived the Hama massacre, those affected by the recent civil war, and a control group who immigrated to Jordan before 1980. They collected DNA samples from 138 individuals across 48 families, focusing on mothers and grandmothers who were pregnant during violent events and their children. They discovered 14 specific areas in the genome of the grandchildren of Hama survivors that bore stress-induced modifications. Additionally, 21 epigenetic sites were altered in those who directly experienced violence. Another finding showed that individuals exposed to violence in the womb exhibited signs of accelerated biological aging, potentially increasing their vulnerability to age-related diseases. While the long-term effects of these modifications remain uncertain, past research suggests links between stress-induced epigenetic changes and health conditions like diabetes and obesity. A well-known study on Dutch famine survivors found similar genetic imprints affecting their offspring’s metabolism. Beyond scientific discovery, the study highlights the resilience of affected families. Despite enduring immense hardship, they continue to build meaningful lives. These findings are likely relevant beyond war zones, shedding light on how various forms of violence—domestic abuse and gun violence—can have lasting biological consequences.

The New Hypothesis for Mars' Red Color Suggests a Once-Habitable Past

Valantinas et al. Detection of ferrihydrite in Martian red dust records ancient cold and wet conditions on Mars. Nature Communications, February 2025.

Mars' iconic red color has long fascinated scientists, and a new study suggests that the water-rich iron mineral ferrihydrite may be responsible for the planet’s reddish hue. A recent work challenges the prevailing theory that hematite, a dry, rust-like mineral, is the primary cause. Ferrihydrite forms in water-rich environments, unlike hematite, which typically develops in drier conditions. This discovery supports the idea that Mars once had liquid water and a more habitable environment. The findings suggest that Mars transitioned from a wetter past to its current cold and arid state billions of years ago. To reach their conclusion, researchers analyzed data from multiple Mars missions, including NASA’s Mars Reconnaissance Orbiter and rovers like Curiosity and Opportunity. They combined spectral observations from orbiters with ground-level measurements and conducted lab simulations, recreating Martian dust to study how light interacts with ferrihydrite. By grinding minerals to submicron sizes—1/100th the width of a human hair—the team replicated the fine Martian dust, confirming that its light reflection closely matches observations from Mars. This discovery opens new possibilities for understanding Mars' ancient climate and habitability. Since ferrihydrite forms in the presence of water and oxygen, its widespread presence suggests Mars had conditions far different from its current dry and cold landscape. The findings may also help answer fundamental questions about whether Mars once supported life. However, final confirmation awaits the return of Martian samples, currently being collected by the Perseverance rover. These samples could definitively determine whether ferrihydrite is the key to Mars' red dust, unlocking more secrets about the planet’s history.