An extra yummy Packed Lunch

2 July 2010

 Donut design.
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Donut design.

When I heard that the latest Packed Lunch would be on food psychology, I immediately became very hungry. As the hours counted down the thought of ‘packed lunch’ and ‘food’ led me to an extra large helping of fish and chips…and a cheesecake.

Why do I lack such willpower when it comes to food? Is it something inherent in me, or is it the fault of those nasty devils in the kitchen, wafting their delicious smells of steaks and pies across our building? According to Professor Jane Wardle, health psychologist and Director of the Cancer Research UK Health Behaviour Centre at UCL, it’s a bit of both.

Wardle’s research focuses on the psychological factors influencing obesity.

Weight is highly heritable (we tend to resemble our biological parents), so for years people assumed that weight changes were almost entirely the result of your genes, and there have been several findings to support this. For example, researchers from the Wellcome Trust Sanger Institute and colleagues found that people with a specific variant of a gene called FTO were heavier. But though there have been several headlines about the ‘obesity gene’ over the years, many appear to make only a small amount of difference in weight. It’s likely that a plethora of genes are involved in a web of interactions.  And their influence is likely to be affected by external factors too.

Moreover, the ballooning of obesity cases over the last 25 years belies a purely genetic influence. Such a rapid rise can’t all be due to genetic changes. So what is?

Lifestyle changes have made a difference, as is the rise in convenience foods and 24/7 advertising. And we react strongly to cues like the smell of food (as anyone who’s walked past a bakery will know) – something food outlets actively take advantage of.

Wardle thinks that some people are naturally more “food responsive”, getting more of a kick out of eating than others. These people may therefore be more vulnerable to the presence of a tasty treat or the devilish advertising around them. Be it a sweet or a savoury tooth, some people are more easily affected by external influences and less able to resist temptation.

In one experiment, Wardle gave a group of 8-12 year old children their favourite food for lunch. They were told they could to eat as much as they liked. The kids were then taken to a room to do puzzles – next to a large plate of sweets and biscuits. Again, the kids were told they could eat as many of these as they liked.

The researchers weighed the plate of sweets and biscuits before and after the experiment. Given that the children should have all been full, surely most of the treats would go untouched? The results were surprising. Some kids indeed ate little or none of the food, but others ate a lot. Their relative fullness appeared to have no effect on how much they ate.

Interestingly, the experiment showed that a child’s body weight was a good predictor of how much they would eat: those with larger weights were more likely to eat more, despite being ‘full’.

Wardle theorises that people vary in the strength or recognition of ‘full’ signals in their body: those who have weaker ‘stop’ signals will easily eat more than they need to. And this doesn’t mean they binge on donuts and KFC – the amount that they overstep might just be a small amount each meal, so they don’t notice. But over time this leads to a gain in weight.

Can we find ways to help people notice their internal stop signals, or consciously change their eating behaviours? The only intervention that has worked so far is the rather extreme vertical banded gastroplasty (VBG), also known as stomach stapling. Wardle also warned that, when it comes to dieting, anything that involves mentally resisting temptation is only a short-term fix and does not tend to change long-term behaviour.

One thing Wardle is experimenting with is ‘unconscious training’ using a cognitive task that trains subjects to unconsciously look away from a ‘bad word’. By replacing the words with pictures of food, she is looking at whether a few minutes of brain training could set you up to ignore food temptations for the rest of the day.

In the meantime, what can I do to cut down the calories and resist that mid-afternoon cake break? Wardle ended her talk with a few practical tips:

1)   go for regular meals at the same time and place to reduce impulse eating

2)   make each meal gradually healthier

3)   make them gradually a little smaller

4)   weigh yourself every day and plot this on a graph so you can track your progress.

I’m putting away that Mars bar right now…