Losing weight is a popular New Year's resolution, but recent research suggests people tend to buy the greatest amount of food and calories after the holidays.

Researchers found consumer spending on food increased by 15 percent over the holiday seasons, and these purchases included higher levels of junk food, the University of Vermont. Shoppers were observed to buy the most food after New Year's, including 9 percent more calories than during the holidays.

"People start the New Year with good intentions to eat better," said Professor Lizzy Pope of the University of Vermont, who led the study as a post-doctoral researcher at Cornell University's Food and Brand Lab. "They do pick out more healthy items, but they also keep buying higher levels of less-healthy holiday favorites. So their grocery baskets contain more calories than any other time of year we tracked."

To make their findings the researchers recruited more than 200 households in New York State and had them participate in a seven-month study of grocery spending spanning from July 2010 to March 2011. In order to identify the patients' shopping patterns the researchers split the data into three periods: July to Thanksgiving (representing the families' baseline spending); Thanksgiving to New Year's; and New Year's to March. Foods were classified as more or less healthy based on a nutritional rating system.

"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," said co-author Drew Hanks, The Ohio State University, who worked on the study as a post-doctoral researcher at Cornell.

In order to combat overeating after the holidays the researchers recommend substituting  less healthy foods for fresh produce and other nutrient-rich items. They also suggest using written grocery lists and splitting grocery baskets visually to ensure nutritious foods make up at least half of the total purchases.

The findings were published in a recent edition of the journal PLOS ONE.