Can we think ourselves thin?

06 February 2019

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Ask someone what makes people eat, and they’ll most likely say hunger...

A fair statement, you might say, given that the dull ache that accompanies an empty tummy is rapidly relieved by eating something. For decades psychologists assumed that this simple relationship between hunger and eating was the whole story. But now scientists are coming around to the idea that thoughts and feelings can also affect our eating habits. I’m not just talking about how stress can provoke a bout of binge-eating in some people and near-anorexia in others. Rather, I want to focus on the more subtle cognitive processes that influence our food intake.

Why do we even think memory can affect eating? 

Not many people know that the memories of our past meals play a crucial role in managing our food intake. The most extreme example of this is patients with amnesia, who are unable to form new long-term memories, including memories of the meals they've just eaten. In one experiment, amnesic patients happily ate two full plates of dinner, one after the other, without feeling much more satiated than before the meal. In fact, when one of the over-fed patients was asked about his plans for later that day, he said he would “go for a walk and get a good meal”. This is in stark contrast to control subjects without memory impairments who refused to continue eating after the first portion, claiming they were too full to continue. Although there are a lot of caveats to consider when drawing conclusions from studies on brain-damaged patients, these findings are one of the reasons why psychologists first became interested in the relationship between memory and eating. It seems that, without remembering a recent meal, we are unable to feel satiated by the food we eat.

Distractions during meal times increase our food intake

So how does knowing that meal memories are important in regulating eating apply to people without brain damage? It turns out that the quality of a meal memory can affect eating patterns of people like you and me, which has some BIG implications for fighting the obesity crisis. But one step at a time. It has been shown that not paying attention to a meal leads to a weaker memory of that meal, which in turn increases the amount of food we then eat. Not paying attention to our meals is something most of us are guilty of, as watching TV, listening to music or playing games whilst you eat have all been shown to increase food intake. When asked to recall the food that they ate, participants who were distracted whilst eating were less accurate in their recall and had less vivid memories of their meals. So, similarly to amnesic patients, we will eat more food if we don’t have a clear memory of our previous meal.

How can meal memories decrease food intake?

At the beginning of this article I promised to describe how our thoughts could help us lose weight, but so far I have only focused on how they can increase the amount of food we eat. That’s because once we understand how poor meal memories can increase our eating, we can start to think about the ways to make these meal memories stronger and more vivid. One such strategy is focusing on our meal when we eat. This is something psychologists refer to as ‘mindful eating’, which basically means we should focus on the taste and texture of our meal, whilst being aware of every bite we take. Although this might not seem as thrilling as entertaining yourself with a new episode of your favourite series, being mindful of our meals can greatly reduce the amount of food we eat. It has also been shown that paying attention to the sensory experience of eating makes the eating episode feel more pleasurable, despite less food being consumed overall. Mindful eating works because we focus on the food we eat, and therefore form better meal memories, which then help keep us satiated for longer.

But paying attention to the food we eat is not the only way to make our meal memories stronger: remembering what you recently ate can also have similar intake-reducing effects. In one study, researchers asked participants to either recall their journey into the lab (control group) or to recall a meal they recently ate (their lunch). Participants were then asked to complete a bogus taste test, during which they could eat and rate a variety of biscuits. They were given 10 minutes to complete the task, but most completed it before the time was up, giving participants a chance to snack freely on the biscuits. It was found that those who recalled a recent meal before snacking on biscuits ate significantly fewer of them, compared to those who recalled something else. Therefore, it was concluded that reminding people about their most recent meal can decrease the amount of food they then eat (or at the very least, the number of biscuits they snack on!).

A new way to fight obesity?

At this point it should not surprise anyone that our society is facing an obesity crisis, with overweight rates sky-rocketing for both children and adults. New interventions, strategies and plans are being devised all the time in order to try and fight this crisis, but these do not seem to be effective, as obesity rates increase every year. Why do we find it so hard to lose weight? The simplest answer is that it’s a cognitively exhausting process, that takes commitment, strong-will and perseverance. Our brains are hard-wired to seek out food, especially that which is high in sugar and fat, so fighting our instincts in obesogenic environments (that is, environments which are full of calorie-dense foods, making it easier for us to gain weight) is an extremely difficult task. A quick Google search reveals that strategies to lose weight, which don’t require this type of cognitive restraint, are in high demand. This is why food-focus and meal-recall based interventions are particularly well suited to be the next obesity-fighting strategies – focusing on or recalling a recent meal does not require a lot of restraint, or even thinking!

So far, there isn’t enough research on the topic to predict with certainty whether focusing on the experience of eating food (mindful eating) or recalling a recent meal before eating the next one can lead to weight-loss. One experiment, which tested whether a mindful-eating smartphone app could help people to lose weight, found that participants were able to lose about one and a half kilograms in a month. However, only 12 people were tested, as the study examined initial feasibility of the intervention, rather than whether the app could bring clinically significant findings. Nevertheless, the findings of this study are promising and suggest that with further research, memory-based apps might help us lose extra kilograms.

Conclusions

To answer the title of this article – yes, our thoughts can help us to lose weight. Maybe. For now, it’s a promising idea which requires further research. It is clear that meal memories are tightly linked to how much we eat at the next meal – it makes sense for our brains to take into consideration our last meal when making a decision whether or not we should eat. Without the ability to form new memories, our bodies are completely out of sync when it comes to eating, as seen in amnesic patients who can eat multiple meals and not feel full afterwards. In people without brain damage, meal memories still have a great influence over their eating patterns. Making a memory stronger and clearer by focusing on the food and avoiding distractions can reduce the amount of food we eat at the next meal. Making a memory of our lunch more recent and more available in our minds before eating can also decrease the number of calories we then eat. Although the exact mechanisms of these effects are not yet clear, the benefits they bring can make a real difference in our society.

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