Is it really more expensive to eat healthy? A U.S. Agriculture Department study found that most fruits, vegetables and other healthy foods cost less than foods high in fat, sugar and salt.

That counters a common perception among some consumers that it's cheaper to eat junk food than a nutritionally balanced meal.

The U.S. government says it all depends on how you measure the price. If you compare the price per calorie — as some previous researchers have done — then higher-calorie pastries and processed snacks might seem like a bargain compared with fruits and vegetables.

But comparing the cost of foods by weight or portion size shows that grains, vegetables, fruit and dairy foods are less expensive than most meats or foods high in saturated fat, added sugars or salt.

That means bananas, carrots, lettuce and pinto beans are all less expensive per portion than french fries, soft drinks, ice cream or ground beef.

"Using price per calorie doesn't tell you how much food you're going to get or how full you are going to feel," said Andrea Carlson, scientist at the USDA's Economic Research Service and an author of this week's study.

For example, eating a chocolate glazed donut with 240 calories might not satiate you but a banana with 105 calories just might.

In the comparisons, the USDA researchers used national average prices from Nielsen Homescan data, which surveyed a panel of households that recorded all food purchases over a year from retail outlets.

Empty calories and hunger

The cost of eating healthy foods has been the subject of growing debate as experts warn Americans about the dangers of obesity. More than a third of U.S. adults are obese, according to the government, and researchers expect that number to grow to 42 per cent by 2030.

"Cheap food that provides few nutrients may actually be `expensive' for the consumer from a nutritional economy perspective, whereas food with a higher retail price that provides large amounts of nutrients may actually be quite cheap," the study said.

The USDA study criticizes a 2010 report from researchers at the University of Washington, which found that calorie-for-calorie junk food is more cost-effective for low-income people than eating healthy.

Adam Drewnowski, director of the Nutritional Sciences Program at the University of Washington and lead author of the prior study, said he stands by his findings that a healthier diet generally costs more. He said there is no government recommendation for how many pounds of food an American should eat each day, but there are federal guidelines that suggest a 2,000 calorie diet.

"Some of these calories are in fact empty calories, so from the standpoint of nutrition they are not terrific," Drewnowski said. "But the empty calories keep you from being hungry, and this is why people buy them, especially lower-income people."

Earlier this week, UN special rapporteur for food Olivier De Schutter sparked a debate on whether Canadians have trouble affording to feed themselves, with the government arguing De Schutter was wasting his time and advocates for the poor urging politicians to create a national food strategy.

Margo Wootan, a nutrition advocate with the U.S. Center for Science in the Public Interest, said some people don't think they get as much value from fruits and vegetables as they get from other foods.

"If they buy a bag of chips for $2, they think it's a good deal, but if they buy a bag of apples for $2, they think it's a lot," Wootan said. "We need to do more to help people understand that fruits and vegetables are not as expensive as they think they are."

Wootan said shopping smart can make healthy eating more affordable. Consumers should be more flexible about choosing less expensive fruits and vegetables that are in season and supplementing those with frozen or canned fruits and vegetables so they don't have to throw away as much.