ABSTRACT
Working memory, the ability to actively store and manipulate information, is considered critical in normal everyday function and contributes significantly to other areas of cognition. Accumulating data show that learning and memory function, including some aspects of working memory, are influenced by diet and metabolic status. It has long been established that nutritional deficiency produces impairments in many domains of cognitive performance (for review, Del Parigi, Panza et al. 2006); however, modern Western cultures are no longer plagued by nutrient deficiency. Rather, the United States, the United Kingdom, and various other Western cultures appear to be facing an epidemic of excessive nutrient intake. In fact, obesity rates in the USA have increased by 75 percent since the early 1980s, with over one-third of adults now classified as obese (Ogden, Yanovski et al. 2007; CDC 2011) as defined by a body mass index (BMI) of greater than 30. In the UK, obesity rates have risen to now include approximately 25 percent of the adult population (Department of Health 2011). Obesity has recently been declared the second leading cause of preventable deaths in the USA, with average attributable annual healthcare costs nearly doubled since 1998 (Finkelstein, Trogdon et al. 2009). Given these alarming trends, a more relevant consideration of the influence of diet and metabolic status on cognition is what the effects of excessive energy intake and body weight gain are on memory function. Given how recently this “obesity epidemic” developed (within the past 20 years), researchers are only beginning to discover the effects of being overweight, obese, and consuming unhealthy high-calorie foods on cognition and neuropsychological function. The emerging picture is that while increased BMI and obesity are associated with impairments in working memory and other domains of cognitive function, certain dietary components that are commonly found in a Western diet, including saturated fat and simple carbohydrates (e.g., sugars), can have detrimental effects on brain substrates that control memory function, independent of the ability of these same dietary factors to contribute to obesity development. Further, both dietary factors and obesity are associated with the development of Alzheimer’s disease and other forms of dementia (Kalmijn, Launer et al. 1997; Berrino 2002; Kanoski and Davidson 2011), which underscores the need for a better understanding of the relationships between diet, metabolic status, brain function, and cognition.
