We tend to blame the obesity epidemic in the United States on people making the wrong lifestyle choices -- for example, eating a Big Mac instead of carrot sticks or Twinkies instead of an apple.
New research shows, however, that the price of healthy food may be too high for many low-income families to afford, and experts say the government needs to step in.
A new study published in the journal of the American Dietetic Association finds that a low-income family would have to devote 43 to 70 percent of its food budget to fruits and vegetables to meet the 2005 Dietary Guidelines, which recommends five to nine servings of fruits and vegetables a day.
"Most Americans fall short of the recommended servings," says Milton Stokes, a registered dietitian and a spokesman for the American Dietetic Association.
"The lower their economic status, the more of their income is spent toward food," he says. "Someone making $20,000 is going to spend a larger percentage of dollars on food than someone making $200,000, even if they buy the same amount."
Currently, researchers say that American families spend 15 to 18 percent of their budget on fruits and vegetables.
"It seems unlikely that consumers would be able to increase their spending on fruits and vegetables by 200 percent to 400 percent without substantial changes elsewhere in the food budget, or from other household expenditures," the authors of the report note. "For low-income consumers this may be especially challenging, because there are few discretionary funds available in these other accounts."
Fruits and vegetables tend to be more expensive than processed foods for a number of reasons.
Fresh produce has a short shelf life, which means that it spoils and therefore can't be bought in bulk and stored in the same way processed or preserved foods can.
Fruits and veggies also lack the backing of government subsidies, such as those for products like high fructose corn syrup, and they can't be mass produced in an automated assembly line. We just have to wait for nature to ripen the apples.
However, reducing the price of fruits and vegetables will not necessarily cause people to eat them more often. Dr. David Katz, director of the Prevention Research Center at the Yale University School of Medicine, explains how the problem is cultural as well as financial.
"If you took the price of fruits and vegetables down by 10 percent, consumption would not increase," he says. "There are barriers that go beyond the issue of price. For example, if you pay for health insurance, it doesn't mean that health care improves.
"The same holds true with fruit consumption. If the cost of fruits and vegetables is cut in half, you are still going to have people who aren't used to eating them and who don't know how to incorporate them into their diets. Habits have to change. Reducing the financial barrier is only the first step."
And even if people are able to afford produce, a bag of carrots isn't going to fill you up the way a Snickers bar does.
"The major concern for low-income groups is not to be hungry at night," says Adam Drewnowski, director of the Center for Obesity Research at the University of Washington in Seattle. "They gravitate to foods that fill them up -- foods that are high in fat and sugar. For them, vitamins and minerals are a luxury."
Furthermore, availability can also present a problem for low-income families.