Cruise ship passengers put on an average 6kg during a two-week holiday, a new study has found.

The poll of more than 1,000 people by UK cruise agency Bonvoyage.co.uk found passengers put on around 450g a day on average thanks to the all-inclusive nature of such holidays.

About 84 per cent of those polled said they consumed more than they normally would, while three in ten doubled their usual number of calories, the Daily Mail reports.

Nine per cent put on some 1.8kg while another six per cent admitted to piling moer than 8kg.

Getting rid of the weight once they returned home was difficult, with 41 per cent saying they found it a challenge to lose the unwanted kilograms.