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A new review summarizing what is known about economic factors linked to increasing obesity in the United States dispels some widely held beliefs and concludes that cheap food has fueled the obesity epidemic .
The review, published in the journal CA: A Cancer Journal for Clinicians, notes that rising obesity rates have been accompanied by increased rather than decreased leisure/free time, increased fruit and vegetable availability rather than a decline in healthier foods, and increased exercise uptake.
After examining all the data, the researchers say the widespread availability of inexpensive food appears to have the strongest link to obesity. Indeed, measured as a fraction of disposable income, Americans have the cheapest food in history. Spending of disposable income on food went from 25% in the 1930s to 20% in the 1950s. The graph below shows the trend since 1970. The share today is less than 10% of disposable income.
The authors say that other factor also have contributed to obesity: cars, increased electronic entertainment, a shift in jobs away from those with physical demands, and increased urbanization. However, the evidence for those associations is less strong. The authors state that:
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. Average daily discretionary calories from salty snacks, cookies, candy, and soft drinks now exceed the discretionary calories recommended in the Dietary Guidelines for energy balance and essential nutrients and the ratio of consumed to recommended discretionary calories is a significant predictor of BMI in the population.
The review concludes by suggesting that policy interventions that focus on positive messages, such as eating more fruit and vegetables or increasing physical activity, may not be the best approach, since more variety means more eating, not less. A more promising tactic is an emphasis on reducing discretionary caloric intake, particularly sugarsweetened beverages and salted snacks.
- Sturm and An. Obesity and economic environments. CA Cancer J Clin. 2014 May 22. doi: 10.3322/caac.21237. [Epub ahead of print]