Obesity – a review

Line-graph showing the average calories consumed per day by Americans from 1970 to 2010
From Sturm, R. and An, R. (2014), Obesity and economic environments. CA: A Cancer Journal for Clinicians, 64: 337–350. doi:10.3322/caac.21237

One of the main contributors to the rising costs of health care is obesity. In 2014, CA published a report called “Obesity and economic environments” that addresses what factors lead to obesity. The authors focus largely on what they call “economic and policy environments”, which is basically any government intervention that shows up when a consumer purchases a product, such as a tax or a subsidy, a limit on serving size, a nutrition label, etc. (These are distinguished from “social environments” -factors influencing a consumer’s choice in food purchases- and “physical environments” -opportunities for consumers to expend energy.) Here is a review of the report’s highlights and conclusions. Recognizing that this information is now 3 years old, I’ll follow up on some of the main points and update as needed.

First, the report makes a few fundamental observations worth noting:

  • Obesity increases the risk of at least 9 different types of cancer, in addition to coronary heart disease, type 2 diabetes, hypertension, stroke, and other chronic illnesses.
  • In developed countries, obesity is by far a greater problem than food scarcity.
  • “Americans now have the cheapest food in history when measured as a fraction of disposable income.” Less than a century ago, Americans spent 25% of their income on food. Now it’s less than 10% (even while the bottom fifth of American incomes still spend a third).
  • Americans have increased their number of calories consumed per day by more than 20% in less than 50 years, going from about 2100 calories per day in 1970 to more than 2600 in the mid-2000s, and dropping only slightly since then.
  • The greatest single source of the increased calories since 1980 has been carbohydrates. Only recently have carbs shown a decline, being replaced by fats.
  • SSB (sugar-sweetened beverage) consumption continues to go up, both in the number of people drinking them and the amount each person drinks.
  • Policies of the USDA have created “a vicious cycle” of encouraging “a massive overproduction of corn and soybeans”, slashing the prices (and thus increasing consumption) of derivative products, many of which show up on those lengthy ingredient lists for processed, prepackaged foods.

Second, the report confronts some common assumptions related to the obesity epidemic that are either too simplistic or flat out wrong.

  • A sedentary lifestyle is not on the rise: The Centers for Disease Control and Prevention Behavioral Risk Factor Surveillance System (BRFSS) “has demonstrated a consistent decline in sedentary behavior.”
  • Leisure-time physical activity has risen, not fallen.
  • Fruits and vegetables have actually increased in the American diet since 1970, even though they still remain below the recommended levels.
  • Locating “food deserts” is not a very accurate way of determining consumption habits of the people in those communities. “Across numerous studies, distance to various types of food stores demonstrated no relationship to dietary outcomes.” This study argues that the real issue is poverty, not access (the study is reviewed here and here). Furthermore, the idea that supermarkets create healthy environments “is a unique United States concept. Elsewhere, the growth of supermarkets has been deplored as reducing access to fruits and vegetables and even increasing prices for fresh produce” because they often take the place of stores dedicated to fruits or vegetables rather than processed, prepackaged foods. Individual cases of obesity can be attributed to one’s access to healthy foods, but the overall rate of incidence for obesity has no such correlation.

Finally, the conclusions. Many of the ideas floating around in the gastrosphere on how to combat the obesity epidemic are either wrong or insufficiently supported by evidence; in the case of the latter, further studies might show support, or might not. What we do know (or did know in 2014), is this…

“Based on empirical evidence and expert opinion, 3 recommendations have been supported by a broad group of health economists in the obesity area:

  1. incorporate health impact assessments to review agricultural policies so that they do not have a deleterious impact on population rates of obesity;
  2. implement a tax on SSB;
  3. examine how to implement fruit and vegetable subsidies targeted at children and low-income households.”

So while it may not be “politically feasible” to institute a national food policy that covers farm to cash register, or to levy taxes on sodas, or to create higher nutritional standards for school lunches, these are the types of things that show promise in addressing the obesity epidemic. What seems clear from the available evidence is that there are too many variables in the national diet for personal choice to make the shift without a policy nudge. Better nutrition saves lives and money. Contact your elected officials and support evidence-based improvements to our food system.

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