Despite New Year's resolutions to eat better and lose weight, people buy the greatest amount of food after the holidays, according to a study led by University of Vermont researcher Lizzy Pope.

"Surprisingly, grocery baskets contained the most calories after New Year," Pope said.

The study, published by PLOS ONE, found that consumer spending on food increases by 15% over the holiday season (Thanksgiving to New Year), with most of the increase attributed to higher levels of junk food.

However, shoppers buy the greatest amount of food after New Year — the equivalent of a 9% increase in calories above holiday levels, Pope said. She led the study as a post-doctoral researcher at Cornell University's Food & Brand Lab.

"People start the New Year with good intentions to eat better," said Pope, who recently joined the University of Vermont department of nutrition and food science. "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."

The findings are surprising given the holidays' reputation for overeating — and suggest that people need better strategies for shopping under the sway of "res-illusions," the research team said.

The researchers recommend that consumers use written grocery lists to deter impulsive junk food purchases; substitute as much junk food as possible with fresh produce and nutrient-rich foods, and split grocery baskets visually to ensure nutritious foods represent at least half of purchases.