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In a preliminary study published in The Quarterly Journal of Experimental Psychology, researchers from the Department of Psychology at Cambridge found an association between high body mass index (BMI) and poorer performance on a test of episodic memory.
Although only a small study, its results support existing findings that excess body weight may be associated with changes to the structure and function of the brain and its ability to perform certain cognitive tasks optimally. In particular, obesity has been linked with dysfunction of the hippocampus, an area of the brain involved in memory and learning, and of the frontal lobe, the part of the brain involved in decision making, problem solving and emotions, suggesting that it might also affect memory; however, evidence for memory impairment in obesity is currently limited.
The researchers tested 50 participants aged 18-35, with body mass indexes (BMIs) ranging from 18 through to 51 - a BMI of 18-25 is considered healthy, 25-30 overweight, and over 30 obese. The participants took part in a memory test known as the 'Treasure-Hunt Task', where they were asked to hide items around complex scenes (for example, a desert with palm trees) across two 'days'. They were then asked to remember which items they had hidden, where they had hidden them, and when they were hidden. Overall, the team found an association between higher BMI and poorer performance on the tasks.
"We're not saying that overweight people are necessarily more forgetful," cautions Dr Cheke, "but if these results are generalizable to memory in everyday life, then it could be that overweight people are less able to vividly relive details of past events - such as their past meals. Research on the role of memory in eating suggests that this might impair their ability to use memory to help regulate consumption.
"In other words, it is possible that becoming overweight may make it harder to keep track of what and how much you have eaten, potentially making you more likely to overeat."
Dr Cheke believes that this work is an important step in understanding the role of psychological factors in obesity. "The possibility that there may be episodic memory deficits in overweight individuals is of concern, especially given the growing evidence that episodic memory may have a considerable influence on feeding behaviour and appetite regulation," she says.
Source material from University of Cambridge