01/07/2015 01:32 EST | Updated 03/09/2015 05:59 EDT

Food purchases, calories go up after holidays

Grocery shoppers seem to buy more junk food not only over the holidays, but well into the new year, a U.S. study suggests.

The holidays have a reputation for overeating, and resolutions can focus on eating healthfully.

But when researchers compared how much shoppers bought over a seven-month period, they found they tended to choose more healthy items but also loaded up foods rich in calories, fat, sugar and salt.

For the study, "New Year's Res-Illusions: Food Shopping in the New Year Competes with Healthy Intentions," researchers looked for shopping patterns among 200 households in New York state based on their grocery spending over three time periods:

- U.S. Thanksgiving to New Year’s Day, the holiday period.

- New Year’s to March, the post-holiday period.

- July to Thanksgiving, the baseline amount.

Calories purchased each week increased 9.3 per cent (450 calories per serving/week) after the new year compared with the holiday period, and increased 20 per cent (890 calories per serving/week) compared with baseline.

"Despite resolutions to eat more healthfully after New Year’s, consumers may adjust to a new 'status quo' of increased less-healthy food purchasing during the holidays, and dubiously fulfill their New Year’s resolutions by spending more on healthy foods," Prof. Lizzy Pope of the University of Vermont and her co-authors at Cornell University concluded in the journal PLOS One.

People seemed to hang on to their holiday junk food favourites, said study co-author Drew Hanks.

In a release, the  researchers suggested consumers:

- Use written grocery lists to deter impulsive junk food purchases.

- Substitute less healthy foods for fresh produce and other nutrient-rich foods instead of just adding healthy foods to the cart.

- Split the grocery basket visually to serve as a reminder to choose nutritious foods for at least half of purchases.

The researchers acknowledged several assumptions, such as their focus on spending rather than consumption or objective measurements of weight gain, and the trends weren’t followed for an entire year.

They also didn’t take into consideration how post-holiday sales on groceries could influence purchases and how people may have more guests at home during the holidays.

The participants were all given a 10 per cent discount on items rated for their nutritional value during the baseline period.