Adiposity, diet or inactivity - which is the culprit in obesity-related memory deficits in human adults?

OBJECTIVE: Obesity, diet and physical activity have independently been shown to impact cognition and memory. However, these factors have rarely been considered together in humans, and thus their relative contributions to cognition remain unclear. DESIGN: The present study explored the relative associations between obesity-related factors and episodic memory in the same sample. METHOD: 64 adults (aged 19-47, BMI 17-37) were assessed using multiple measures, including dietary report, activity monitors, and a range of anthropometric bodyfat measurements. Alongside these, related variables including blood pressure, eating behaviour, depressive symptoms, sleep quality and IQ were also measured. Participants' memory was assessed on a what-where-when (WWW) memory test (the Treasure-Hunt Task) that measures item, spatial and temporal memory for a specific encoding episode, as well as the ability to integrate these into a single coherent WWW memory. RESULTS: It was found that dietary cholesterol negatively predicted variance in both WWW and temporal memory when all other factors were taken into account, and that adiposity also negatively contributed to variance in temporal memory. CONCLUSIONS: These findings suggest that diet and adiposity may independently impact cognition, rather than one being a mediating factor for the other. A review of potential mechanisms indicates that both diet and adiposity may influence cognitive and memory ability via systemic- and neuroinflammation.