Dr Lucy Cheke, University of Cambridge
There are many well known health risks associated with being overweight, including heart disease, diabetes and increased risk of stroke. However another potential cost to being overweight is your memory. Research is also starting to point to a worse memory leading to overeating, as people are less likely to remember how much they've consumed in a day. Lucy Cheke, a psychologist from Cambridge University, told Chris Smith about the research, and offered some pointers to avoid this forgetful eating. She started by explaining how being overweight could affect your memory.
Lucy - Well, itís a very complicated process and itís something that we don't fully understand at the moment. But lots of research both in animals and humans seems to suggest that all the different routes you can get obesity from. So, eating a high fat, high sugar diet or having a genetic issue that causes you to become obese can all lead to changes in your brain. As Giles said earlier, a lot of the genes that we have that control our eating and how we gain weight act in the brain. And so, when you change things in the brain, sometimes you can change how the brain works in a number of different ways as well as on top of why we eat and how we eat.
Chris - What's the evidence that you've got that if someone does gain weight that their memory does go off kilter and by how much does their memory go off kilter?
Lucy - So, this research area is really very young at the moment. So, weíre still discovering things all the time. my own research over the last couple of years has looked at overweight and lean people and compared them on memory tests. What we found is that there's about a 20% difference in memory ability between young, otherwise, healthy overweight people and their lean counterparts. We followed that up with a brain scanning study where we looked at the areas of the brain that are associated with memory whilst people are doing this memory test. We found that again, young healthy obese individuals had less activity in the memory-related brain areas. So, the brains did seem to be responding differently.
Chris - But I presume what you didnít do was to take someone slim and put them on a Bridget Jonesís Diary force feeding diet to make them gain a load of weight and then re-assess their memory to see if their memory deteriorated having gained weight or have you done that?
Lucy - We haven't done that and that's something weíd really like to do. Obviously, that's something that takes a lot of money and resources and you need to get people willing to come and take a high fat, high sugar diet.
Chris - But has anyone done the equivalent in an animal study because you could for instance force feed a mouse? Just give it too much food and see if the mouseís memory suffers.
Lucy - Yes, absolutely and people have done that. so, people have taken rats and put them on whatís called a cafeteria diet. Itís a very high fat, high sugar diet where they only have access to really unhealthy foods. What they found is that overtime, these rats gained weight as you'd expect, but they also showed learning and memory deficits and they also found that they had significant changes in the bits of their brain that dealt with memory. So yeah, people have done this in animals. It does seem to have a big effect.
Chris - Do we actually know why the junk food diet is damaging memory and is it reversible? If you slim down your mouse or your rat again, does the effect go away?
Lucy - Well, so it seems that perhaps it does. The research in that direction hasnít been done quite so much. In terms of why it happens, we still don't know. The kind of leading theories are that itís to do with insulin. That even if you're not diabetic per se, if you're overweight then quite often, your insulin levels are different and you fast and your insulin sensitivity is different. Insulin as we know acts in the body to control how much we eat in our blood glucose. But it also acts as a messenger in the brain. And if its ability to act as a messenger in the brain is disturbed, that has a lot of effects in all the areas that rely on it to send messages.
Chris - How might this decrement in memory in someone whoís gained weight affect their ability to be compliant with their diet and lose weight afterwards?
Lucy - Well actually, itís really interesting. So, there's been some research showing that what we remember about what weíve eaten can dictate how we hungry we feel several hours later, say, the next meal time. so, if we for example watch TV during a meal and don't remember the meal very well, then later on, we can be a lot hungrier than if we concentrated really hard on the meal. Actually, if you trick people into thinking they ate a different amount than they actually ate, then you find that how much they think they ate dictates how hungry they are later on whereas how much they actually ate only dictates how hungry they are immediately after the meal.