With winter coming to an end, many people are already planning their summer holidays. However, a new study has found what most of us have probably long suspected - holidays lead to weight gain.

US researchers looked at 122 adults aged between 18 and 65, who went on holidays over a six-month period. All of the holidays were between one and three weeks long.

While previous research has linked certain holiday seasons, such as Christmas, to weight gain, this is the first to look at the impact of short-term holidays.

The study found that almost two in three of the participants gained weight while on holidays. The average amount of weight gained was almost a pound, however some participants gained as much as seven pounds.

While such weight gain may not sound like much, the researchers pointed out that it is ‘a pretty substantial weight gain during a short period of time'.

They also noted that it adds to the idea of ‘creeping obesity', which is when adults continually gain small amounts of weight over time, eventually leading to increased health problems.

The study found that on holidays, many people tend to be more active than usual. However, there also tends to be a decrease in physical activity in the weeks after a holiday.

The researchers said that the main reason for holiday weight gain is increased calorie intake, particularly from alcohol. Among the participants in this study, the average consumption of alcohol before their holiday was eight drinks per week. During their holiday, this increased to 16 drinks per week.

"One of the challenges people face is unless you're diligent about weighing yourself before and after vacation, usually you're not going to notice a pound of weight gain. People don't realise it's happening, and that's why they don't lose weight following a vacation," the researchers from the University of Georgia said.

However, it is not all bad news. The study also noted that people were significantly less stressed and recorded a small reduction in blood pressure that lasted up to six weeks after their holiday.

"This may, in part, be explained by the trend for more total activity while on vacation. Whether or not those positive changes in blood pressure and stress can overcome the negative health implications of gaining weight on vacation are yet to be determined," the researchers added.

Details of these findings are published in the journal, Physiology and Behavior.