ATLANTA (CNN) — Forget fancy diets and expensive exercise programs. Fighting fat and keeping a healthy weight may be as easy as food shopping with a grocery list.

People who said they always used a list when they shopped had a healthier weight, even in neighborhoods where there were a variety of obstacles to eating healthy, according to a new study.

This latest data builds on earlier research that showed people may lose weight if they stick to a list when they shop.

To get at this conclusion, researchers went door to door collecting demographic information, height and weight, and details about a person's diet. This was in lower-income neighborhoods in Pittsburgh that are considered "food deserts," meaning residents who live there have few options for healthy food. Most of the residents in the neighborhood had household incomes below $20,000 and the majority were African-American.

What researchers found when they asked more than 1,300 residents about their grocery shopping habits was that nearly a third said they always shopped with a list. Some 17 percent said they sometimes shopped with a list, while 26 percent said they never bothered.

The group that planned before they shopped weighed less than the other groups. On average they weighed at least 5 pounds less than those who did more free-range shopping.

The authors of the study, which was published in the latest edition of the Journal of Nutrition Education and Behavior, caution that this work cannot be directly applied to people with higher incomes; however, lead author Tamara Dubowitz said she "wouldn't be very surprised" to see similar results for other income levels.

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"It makes sense that if you have a list it is a good tool to counteract some of the other influences that are shouting at us at the store, encouraging us to not necessarily engage with healthy food options," said Dubowitz, who is a senior policy researcher with RAND Corporation. One earlier survey of food stores in California found that 71 percent had unhealthy exterior advertising, while only 12.2 percent had ads for healthy food.

If you can plan at home, it can keep you more focused. "Food marketers are good at what they do and their aim is not to make us healthy, it is to sell products," Dubowitz said.

The other reason list makers may be successful at keeping a healthy weight is that the effort may "reflect a conscientious personality."

The ultimate takeaway from the study, Dubowitz said, is that even for people who have huge obstacles to healthy eating, something as simple as planning may have helped. And that's good news, because earlier research has shown that people who live in food-insecure neighborhoods often suffer disproportionally from obesity-related illnesses and chronic conditions.

"Little things like making a list mattered," she said. "This can be an easy strategy we can teach people that could make a real difference." And it may be a simple strategy you could adopt to stay focused at the store and avoid all those high-calorie, fatty food temptations.

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