Changes in the brain during and after dieting have been shown to contribute to the yo-yo effect, where weight is quickly regained after a period of weight loss. Researchers from the Max Planck Institute for Metabolism Research and Harvard Medical School studied mice on a diet to assess which circuits in the brain changed, focusing on a group of neurons known to control the feeling of hunger. They found that neuronal pathways that stimulate these neurons sent increased signals when the mice were on a diet, and this change could be detected for a long time after the diet. Inhibiting the neural pathways in mice that activate these neurons led to less weight gain after the diet, offering new possibilities for preventing the yo-yo effect in humans. Researchers continue to explore how to block mechanisms that strengthen these neural pathways.