Your grandparents and parents may have been fitter and healthier because they spent more of their income on food than you do. According to new research, the availability of cheap, high-calorie food is perhaps the biggest contributor to being overweight and obese, which affect two out of three Americans. But consuming more fruits and vegetables, or exercising, may not be the only solution to losing the excess flab, according to the researchers.

The study appears in the online edition of CA: A Cancer Journal for Clinicians. Economic and technological advancements have led to many modern lifestyle changes, and have therefore resulted in lots of excess leisure time. Many Americans are exposed to factors that lead to obesity, such as television, junk food, automobiles, vending machines, suburban housing developments, and increased portion size.

The researchers reviewed all these possible factors and found that the availability of easy and cheap food is a major reason for America’s growing waistline. In their study, they write, "Americans are spending a smaller share of their income (or corresponding amount of effort) on food than any other society in history or anywhere else in the world, yet get more for it."

Statistics show that in the 1930s, Americans spent one-quarter of their disposable income on food. By the 1950s, that figure had dropped to one-fifth. Currently Americans spend less than one-tenth of their disposable income on food.

Other factors linked to obesity, such as the rise of electronic entertainment, increased use of cars; jobs that don’t require physical strain, and increased urbanization are not major contributors according to the authors. "Examining time trends for which there are data, what jumps out are changes in food availability, in particular the increase in caloric sweeteners and carbohydrates,” they wrote.

The authors tried to assess if the many proposed solutions for reducing obesity such as encouraging exercise, decreasing access to high calorie foods, building more exercise-friendly environments, increased labeling, or even levying taxes on some foods, can make a difference. But while these may be effective to an extent they are not optimal approaches, the researchers said. Emphasis on reduced calorie consumption, particularly with foods that are high in sugars like certain beverages and salted snacks is the key. "Although increasing fruit and vegetable consumption may be a laudable goal for other health reasons,” they wrote, “it is unlikely to be an effective tool for obesity prevention.”

Source: Sturm R, Ruopeng A. Obesity and Economic Environments. CA: A Cancer Journal for Clinicians. 2014.