Consumer spending on food increases by 15 percent over the holiday season (Thanksgiving to New Year), with most of the increase attributed to higher levels of junk food. But shoppers buy the greatest amount of food after New Year - the equivalent of a nine percent increase in calories above holiday levels, said Lizzy Pope from the University of Vermont.

"People start the New Year with good intentions to eat better," Pope noted."They do pick out more healthy items, but they also keep buying higher levels of less-healthy holiday favourites. So their grocery baskets contain more calories than any other time of year we tracked," she pointed put.

For the study, more than 200 households in New York state were recruited to participate in the seven-month study of grocery store spending behaviours, from July 2010 to March 2011.

"Despite New Year's resolutions to eat healthier, people tend to hang on to those unhealthy holiday favorites and keep buying them in the New Year," co-author Drew Hanks from Ohio State University explained. The study was published in the journal PLOS ONE.

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