Review says inexpensive food a key factor in rising obesity

A new review summarizes what is known about economic factors tied to the obesity epidemic in the United States and concludes many common beliefs are wrong. The review, authored by Roland Sturm, PhD of RAND Corporation and Ruopeng An, PhD, of the University of Illinois at Urbana-Champaign, notes that paradoxically, rising obesity rates coincided with increases in leisure time, increased fruit and vegetable availability, and increased exercise uptake. The review appears early online in CA: A Cancer Journal for Clinicians and finds at least one factor fueling the obesity epidemic: Americans now have the cheapest food available in history.

Today, two in three Americans are overweight or obese, with rates climbing steadily over the past several decades. Many factors have been suggested as causes: snack food, automobiles, television, fast food, computer use, vending machines, suburban housing developments, and portion size. The authors say forming a coherent picture is a challenge, but is necessary to assess whether the many proposed solutions, from encouraging physical activity and decreasing access to high calorie foods, to building more exercise-friendly environments, increased labeling, or even levying taxes on some foods, can make a difference.

After examining available evidence, the authors say widespread availability of inexpensive food appears to have the strongest link to obesity. 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." In the 1930s, Americans spent one-quarter of their disposable income on food. By the 1950s, that figure had dropped to one-fifth. The most recent data show the share of disposable income spent on food is now under one-tenth.

The authors review the evidence for other factors, and say the rise of electronic entertainment, increased use of cars, a shift in jobs away from those with physical demands, and increased urbanization also contribute to obesity. But they say the evidence for those associations is less strong, saying: "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."

The availability of cheaper food is the main reason behind the rising rates of obesity in the U.S., says a new analysis published in CA: A Cancer Journal for Clinicians.

The review of existing research on lifestyle habits and health also indicates many of the theories about the growing obesity epidemic may actually be wrong. While other factors have also contributed to the obesity problem - like spending more time in cars, hours in front of computers and TVs, and a shift toward sedentary jobs - the authors' analysis shows the link between obesity and these various factors is less strong.

Instead, after assessing findings of 75 prior papers and reports on lifestyle and public health, the authors conclude access to cheap food is the main driving force behind the obesity epidemic.