There may be a simple way to lose weight using only the power of thought. You just have to know how, says David Robson.

Eric Robinson has a surprising tool for weight loss. It’s something we all have, but perhaps don’t use it as much as we’d like: our memory.

Dieters often feel that they are waging war with their stomachs, but psychologists like Robinson believe that appetite is formed as much in the mind as our guts. So much so that if you try to remember the last food you’ve eaten, thinks Robinson, you can get thinner without the hunger pangs.

“Lots of research has now shown that subtle psychological factors can impact how much you eat – but people still aren’t aware of the influence,” he says. “And that’s important, given the worldwide obesity problem.” If this is true, how could it work?

The inspiration for this latest thinking comes, in part, from people with very poor memories, suffering from a deficit known as anterograde amnesia. You could meet these people and have a deep, involved conversation – but after 20 minutes they wouldn’t have the faintest idea who you were. “Something happens to them, but you come back 20 minutes later and they have no recollection of it,” says Robinson, who is based at the University of Liverpool.

Forgotten food

The same is true of the food they eat. One of the key studies involved a former musician and a former banker, both of whom had developed anterograde amnesia after a herpes infection damaged parts of the temporal cortex, the part of the brain that lays down new memories. They were first given a plate of sandwiches and cake, which they ate until they were full. The plates were taken away – only to be returned with more helpings 15 minutes later. While healthy volunteers would tend to feel too full to eat more, the two amnesic subjects happily filled themselves a second time. “They forget they’ve had their last meal, and so if they are offered another one, they’ll eat that too,” says Glyn Humphreys, at the University of Oxford, who conducted the study.

Despite their poor memories, the amnesic pair weren’t completely oblivious to what they had just eaten. In another part of the experiment, they were allowed to taste a range of foods – rice pudding, crisps, or chocolate, asked to wait a bit, and then offered the plates again. Most people, like you or I, seek a variety of flavours, so we change our preference a second time round – a phenomenon called “sensory specific satiety”. Like us, the two amnesic volunteers also felt less tempted by their previous choice – even though they said they had no recollection of having eaten it. Their changing preference suggests they didn’t have a problem with the sensory processing of the dishes – it’s just they couldn’t form an explicit, conscious memory of the meal. And without that recollection, they still felt hungry, even when their stomachs were full.

You might suspect that a healthy brain is smart enough to take notice of what you’ve eaten, but recent research shows it is easily fooled. Consider this ingenious experiment by Jeff Brunstrom at the University of Bristol. His subjects thought their task was simple: to eat a bowl of soup. Unbeknown to them, Brunstrom had hooked up a pipe that passed through the table and into the bowl, which allowed him to top-up some of his subjects’ soup without them noticing. He found that their later snacking depended almost entirely on the appearance of the bowl at the start of the meal – whether it seemed big or small – and very little on the actual amount he had fed them.

All of which weakens the common notion that hunger is governed solely by the hormones from the gut. “I’m not suggesting that kind of signalling isn’t important, but the role of cognition has been under represented,” says Brunstrom. And in some circumstances it may be more important.

That could easily have an impact in our hectic, modern lives. Working lunches are now commonplace in most offices, and many people watch TV or play with their smartphones and laptops during evening meals. All of these distractions might affect your memories of what you’ve eaten. Brunstrom, for instance, asked subjects to eat with one hand while they played solitaire with the other. Thanks to the distraction, they struggled to recall the meal, and pigged out on more biscuits later in the day.

Sensory boost

It is for this reason that the researchers are now looking into ways of boosting the sensory memory of food. Robinson recently tested whether a recording, played during a meal, could help a group of obese women to eat some ham sandwiches more mindfully. The instructions were simple: the 3-minute clip asked them to focus on the full sensual experience of the meal – the sights, the taste, and the smell. A second control group ate with the pleasant sound of a cuckoo’s melodious calls. As Robinson had hoped, the people asked to savour their food gave fuller descriptions later on, and snacked less 3 hours later – consuming 30% fewer calories.

The approach may not work for everyone, but Robinson has other ideas for alternative techniques; in another experiment, asking people to consciously remember what they had eaten earlier in the day seemed to discourage over-eating later on. Your imagination may even offer a helping hand: a team in Pennsylvania has found that visualising your cravings, in full detail, seems to trick the mind into thinking it has actually eaten the snack – reducing desire and actual consumption.

Robinson is currently working on an app that could remind someone to recall their previous meals throughout their daily routine. But despite all these efforts, he points out that we still need bigger clinical trials to test if memory tricks are really effective in the ongoing battle with obesity. He’s also concerned that people might find the procedures tiresome – particularly if they have to listen to a recording every time they eat.

Promisingly, “attentive eating” does not seem to reduce his subjects’ pleasure of their meals; on the contrary, they actually seemed to find it more enjoyable to absorb themselves in the sea of flavours hitting their tongues. “It’s not unimaginable that savouring food could actually be a good thing.”

If they work, these memory tricks could therefore offer that rare thing: a slimming programme that actually enhances your pleasure in food. And surely that would be one of the more palatable solutions to the fight against obesity.

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