To answer the question about whether or not being obese damages the mind, Lucy Cheke and her colleagues at the University of Cambridge, invited a couple participants to the lab to navigate a virtual environment on a computer screen. The test was to drop off some virtual objects in a cyberspace maze and then test their memory of the task: where had the objects been hidden?
Before now, we might have assumed that the biggest factor in this test would be the participant’s IQ, not their waistline, however Cheke found a clear relationship between their BMI (a measure of weight relative to height) and memory deficits; the higher their BMI, the worse they performed on the Treasure Hunt task.
Cheke’s hypothesis contributed to a growing, albeit small, body of evidence that links obesity to brain shrinkage and memory deficits. And this research suggests that obesity may contribute to the development of neurodegenerative conditions like Alzheimer’s Disease. The research also seemed to show that the relationship between obesity and memory is a two-way street: being overweight or obese doesn’t just impact memory function but also our future eating.
Her experiment found that the obese participants found it particularly difficult to remember the location of the different objects and this supported not only her hypothesis but earlier findings that indirectly linked obesity to impairments of cognitive function.
From the article:
“Body fat is the defining feature of obesity, but you’ve also got things like insulin resistance, hypertension, and high blood pressure,” says Cheke. “These can go hand in hand with behavioural factors [such as overeating and lack of exercise] and they can all potentially cause changes in the brain.”
“For example, insulin is an important neurotransmitter, and there’s a lot of evidence that diabetes is associated with changes in learning and memory,” she adds, “but there’s also evidence that high body fat on its own leads to inflammation in the brain, which can also cause problems.”
Inflammation is another possible culprit. In previous studies, data from more than 20,000 participants in the English Longitudinal Ageing Study, were looked at to check levels of an inflammatory marker called C-reactive protein. The researchers found that, “greater body mass was associated with a decline in memory function, and also with higher levels of the inflammatory protein.” While the links are indirect, the results suggest brain inflammation might be a plausible mechanism by which differences in ones BMI might influence cognitive function in otherwise healthy, aging adults.
This means that the potential to overeat as we age is possible if our memory is impaired. When testing this, experimental psychologist, Eric Robinson from the University of Liverpool and his colleagues, recruited 48 overweight or obese people and invited them to eat lunch in the lab. They divided the participants into two random groups and gave them audio recordings to listen to while they ate: group one listened to audio instructing them to pay attention to their food, and those in group two listened to an audio book with non-food related content.
The next day they were invited back, presented with some high-energy snacks, and researchers measured how much they ate. Those who had been instructed to focus on their lunchtime meal ate almost one-third less than those who had been distracted by the audio book. Robinson and his colleagues decided to do a larger follow-up study which confirmed their findings.
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“Attention and memory are independent of each other, but they are closely linked – we cannot remember something that we did not pay attention to and, by the same token, our memories of something tend to be more vivid the more we attend to it.
It’s therefore possible that a vivid memory of lunch could reactivate the body’s physiological state, so that we do not feel so hungry, and consequently eat less at dinner. On the other hand, someone who was distracted during lunch would form weak memories of the meal, and so thinking about it at dinner might make them feel hungrier and eat more.”
Until we have enough proof, we should be careful not to draw firm conclusions. But in the meantime, knowing that food memories and awareness can influence eating behavior, does offer an approach to helping people lose weight and maintain a healthy BMI. The next step would be to move from the lab to the real world and the team has developed an app to do just that.
The app encourages people to take photos of what they’re eating and answer questions about their meals, the idea being that creating vivid memories will make them less likely to overeat during the day. Cheke says, “We’re trying to get all these different variables to see the relative contribution, so we’ve got people out wearing activity monitors and filling food diaries for us. Doing studies like this is the only way we’ll be able to tease these things apart.”