19/11/2010 19:00 GMT | Updated 22/05/2015 10:12 BST

Are Small Portions Fooling You Into Overeating?

As anyone who's ever been on a diet knows, portion control is crucial if you want to lose weight. But we could be eating more than we realise when we think we're having small portions, say US researchers.

The bigger the biscuit, the fewer calories you'll eat The bigger the biscuit, the fewer calories you might eat. Photo: MorgueFile, mconnors

Writing in the Journal of Consumer Research, the University of Michigan experts suggest when people are led to believe they're having a small - as opposed to a large - portion, they actually end up having more calories.

In tests the researchers gave volunteers identical plates of 15 biscuits, but labelled some as medium-sized biscuits and others as large biscuits. On average, those who thought they were eating the medium-sized biscuits ate more than the volunteers who believed the biscuits they were eating were the larger ones.

However those who had eaten the medium-sized biscuits said they thought they had eaten less than the volunteers who'd eaten the large biscuits. In other words, even though in reality they'd had more biscuits overall, they didn't realise it.

In another round of tests, the researchers discovered people also eat more than they realise when they're doing other things while they're eating - as opposed to when all they have to concentrate on is their food.

It's all so confusing if you're struggling with your weight. And now, it looks like even if you do try to eat smaller portions, it might explain why your diet's not working.

But it's not the first time experts have suggested there's more to portion control than we realise, with one study claiming we could fool ourselves we're eating more, when actually we're eating less.

When did food get so complicated?

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