In university cafeterias, people select their food before they are seated and perhaps before they know with whom they will eat.

'Given the observed differences it seems likely that social groupings were anticipated at the time of food selection,' she said.

Young said calorific intake by women might be influenced the diet industry that targets female consumers and uses advertisements typically depicting very slim models rather than average-sized or overweight female models.

'So food choices appear to be weighed against how others perceive them. In other words, smaller, healthier portions are seen as more feminine, and women might believe that if they eat less they will be considered more attractive to men.

'It is possible that small food portions signal attractiveness, and women conform, whether consciously or unconsciously.'

She found that men were not much affected by the number or the gender of their dining companions.

The study appears in the online international journal Appetite.