Obesogenic Inflammatory Memory: A New Concept Related to the Dangerous Effects of Weight Cycling.

Obesity is associated with profound metabolic, inflammatory, and neurobehavioral dysfunctions. Dietary interventions leading to weight loss are commonly employed, yet it remains unclear whether all obesity-related alterations are fully reversed upon reaching normal body weight. Poor adherence to dietary regimens often results in weight cycling, or yo-yo dieting, characterized by repeated episodes of weight gain and loss, a phenomenon linked to adverse health outcomes. Here, we investigated the consequences of weight cycling in C57BL/6J mice. The Control Group was maintained on a standard chow diet throughout the protocol, whereas the experimental group underwent two alternating cycles of high-fat diet feeding (weight gain) and standard diet reversion (weight loss), until the end of the protocol where both groups reached 80 weeks of age. Despite achieving a final body weight and glucose and lipid metabolic profile comparable to lean controls, weight-cycled mice exhibited impaired sensorimotor function, increased anxiety-like behavior (evaluated through behavioral tests), and persistent inflammation, including a peritoneal macrophage pro-inflammatory profile and adipose tissue infiltration. We define this phenomenon as "obesogenic inflammatory memory", highlighting that obesity leaves an immunological imprint that sustains inflammation even after normalization of weight and metabolic parameters. These findings demonstrate that weight cycling is associated with chronic macrophage-mediated inflammatory states, linked to long-term behavioral and neurological manifestations, and opening new avenues for future investigation and therapeutic approaches.