Short-term high-fat diet impairs anterograde and retrograde memory consolidation, but not retrieval in aged rats

BACKGROUND: Aging increases vulnerability to cognitive decline, and ultraprocessed diets high in saturated fat may accelerate this trajectory. Although short-term high-fat diet (HFD) exposure is known to impair memory in aged animals, the specific stages of memory most susceptible to short-term HFD remain unclear. METHODS: This study examined how short-term HFD influences anterograde consolidation, retrograde consolidation, and retrieval of long-term fear memory in aged rats. Male F344 × BN F1 rats (22-24 months) consumed chow or three days of HFD provided at distinct times relative to contextual and cued fear conditioning to isolate each memory phase. Importantly, this brief HFD protocol minimizes metabolic disturbances typically produced by longer-term diet manipulation, allowing us to isolate the effects of macronutrient composition on memory processes. RESULTS: Three days of HFD before or immediately after conditioning significantly impaired contextual and cued fear memory, reflecting disrupted anterograde and retrograde consolidation. In contrast, three days of HFD before retrieval had no effect on memory performance. CONCLUSION: These findings demonstrate that short-term consumption of ultraprocessed HFD selectively impairs consolidation while sparing retrieval of hippocampal- and amygdala-dependent memory in aging. These findings are important because identifying the specific memory processes that are disrupted, rather than global memory dysfunction, helps narrow mechanistic targets and informs the development of more precise interventions to mitigate diet-related cognitive decline in aging.