Being overweight linked to poor memory: study

Overweight young adults may have poorer ability to recall past events than their peers adding a increasing evidence of a link between memory and overeating, according to a new study.

Researchers from University of Cambridge in the UK tested 50 participants aged 18-35, with body mass indexes (BMIs) ranging from 18 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.

The results could suggest that the structural and functional changes in the brain previously found in those with higher BMI may be accompanied by a reduced ability to form and/or retrieve episodic memories, researchers said.

As the effect was shown in young adults, it adds to growing evidence that the cognitive impairments that accompany obesity may be present early in adult life, they said.

"How vividly we remember a recent meal, for example today's lunch, can make a difference to how hungry we feel," said Lucy Cheke from University of Cambridge.

"We are not saying that overweight people are necessarily more forgetful, but if these results are generalisable 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 meal," said Cheke.

Research on the role of memory in eating suggests that this might impair their ability to use memory to help regulate consumption, Cheke said.

"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," she said.

Researchers believe 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," said Cheke.

The results support existing findings that excess bodyweight may be associated with changes to the structure and function of the brain and its ability to perform certain cognitive tasks optimally, researchers said.

In particular, obesity has been linked with dysfunction of the hippo-campus, 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, they said.

The findings were published in The Quarterly Journal of Experimental Psychology.