SHARING a bag of popcorn on the sofa seems like the best approach to snacking while trying to lose weight.
But an expert has revealed how the habit may be causing more harm than good.
Nükhet Taylor, an assistant professor of marketing at Ryerson University in Toronto, Canada, said it was safer to stick to your own food after proving the theory in a set of experiments.
She and colleagues found that when people share food, they underestimate how many calories they are eating.
They not only perceive the food as less fattening, but they eat more of it as a result, and may make worse food choices the rest of the day.
Dr Taylor told The Times: “When we see food on a shared plate, we still understand how many calories we are consuming, but we do not think that those calories will impact our waistline.
“In other words, because the shared plate does not belong to us, it is a common plate shared with someone else, we believe that whatever we eat from that plate will not be of consequence to our weight.
“This, in turn, makes us want to eat more, given that there are no consequences to our food consumption.”
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Researchers said people do not feel as though they “own” food when sharing it, and this causes them to “mentally decouple the calories from their consequences”.
Sharing food is one of the greatest parts of socialising, whether it be chips at a restaurant or sweets in the cinema.
But Dr Taylor said it may be “problematic” for people who want to lose weight “because we end up consuming more calories”.
The research, published in the Journal of Consumer Psychology, involved three experiments with 719 people
In one experiment, people were shown photos of fries and asked to imagine themselves eating 10 chips.
Those who ate from a shared plate deemed the chips as 15 per cent less fattening than those who ate the same amount, but from separate plates.
Those who ate from a shared plate found the chips 18 per cent less fattening compared to those who ate completely alone.
This was despite the fact there was no difference in the actual amount of calories that people said they thought the chips contained in each scenario.
And it’s not just the indulgent snacks that are the problem.
The same amount of almonds were perceived as being 22 per cent less fattening when shared with a friend, compared to a single portion.
Those within the experiment were also given chocolate M&M’s, which they found 20 per cent less fattening when eaten from a shared bowl compared to when eaten alone.
In the final experiment, participants had to imagine being at a McDonald’s and eating a shared box of chicken nuggets.
They were then asked after eating the nuggets to choose a dessert – either apple slices or an ice-cream sundae.
Those who had “shared” the nuggets were 13 per cent more likely to choose the higher-calorie option of ice cream than those who imagined eating their own nuggets.
Dr Taylor said people were using “mental accounting”.
She said people have a “mental budget” in their mind for how many calories they can consume per day in order to maintain their weight.,
But when sharing food that is perceived to be less fattening, people are not accounting for them in their mental food budget.
Next time you go out to eat, it may be worth ordering that side to yourself after all.