by Kenneth W. Krause.
Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer. Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes regularly to Skeptic as well. He may be contacted at email@example.com.
One in three American children were confirmed overweight or obese in 2009.(1) Since then, few if any health statistics have been more widely publicized. Five years later, however, we still don’t seem to understand how we’ve accomplished this for our kids.
Biologists and anthropologists have broadly indicted certain evolutionary mismatches between our contemporary “obesogenic” environment and biological adaptations naturally selected thousands or even millions of years ago (Power and Schulkin, 2009). These incongruities generally fall into two categories.
First, present-day humans are thought to naturally favor inactivity and, thus, to consistently burn too few calories. The role of exercise in body composition control is complicated and somewhat controversial. Regardless, it is not the subject of this column.
Second, Westerners especially are accused of consuming too many total calories or too many inappropriate foods. Diet’s role in the obesity crisis is far clearer and more convincing. Indeed, specific culprits—highly refined carbohydrates, in particular—have been identified.
But a much more practical question remains, implicating both personal behavior and public policy. From what cultural sources does the problem primarily emanate, and in what relative proportions? In other words, precisely where are American children really getting fat?
Myriad scholars and government officials have vigorously impugned the fast food industry. And why shouldn’t they? As the prevalence of overweight and obesity has tripled among American children in the last thirty-five years, the percentage of total energy intake consumed from fast food has risen from two percent in 1978 to thirteen percent in 2006.
Unsurprisingly, fast food outlets continue to stuff their menus with perhaps the poorest nutritional options imaginable. On average, fast foods are higher in solid fat (23.9 % of total energy) than food from either retail stores (17.6 %) or schools (20.9%). Compared with non-consumers, kids who eat fast food receive higher levels of total energy, total fat, and saturated fat. They also consume less fiber, milk, fruit, and vegetables, and more sugar-sweetened beverages and French Fries.
So what’s not to detest about fast food? Very little or nothing at all, we might agree, but that’s not the question at hand. Instead, we might ask whether the evidence truly condemns fast food as a proximate cause of childhood obesity and, if not, whether fast food serves only as a relatively unobjectionable scapegoat for a far more likely suspect.
The Centers for Disease Control and Prevention, one of the main operating arms of the U.S. Department of Health and Human Services, has published an authorless online report titled “Incorporating Away-From-Home Food into a Healthy Eating Plan.” The article focuses on the relationship between childhood obesity and food-away-from-home (FAFH)—including fast food but not school meals.
With about one-third of the average American’s daily calories coming from FAFH, the report opines, “it is important to consider how individuals can fit these items into a healthy eating plan.” Assumed but not supported in this decree is the conviction that Americans who consume significant amounts of fast food are interested in a healthy diet and, if so, capable of recognizing, preparing, and consistently consuming one.
After reciting the familiar nutritional and proportional shortcomings of FAFH, the report references dozens of studies thought to demonstrate a robust association between FAFH and overweight or obesity. One study, for example, found that both adult and child fast food eaters consumed more calories, fat, and sodium, and less vitamins, milk, fruits, and vegetables than non-eaters. Another discovered that states with higher levels of obesity had more fast food restaurants. Other longitudinal studies associated higher frequencies of fast food consumption among girls, boys, and adults with elevated BMIs or adiposity.
In the end, the CDC cautioned that the available literature had yet to conclusively establish a direct causal link between FAFH and obesity. Nevertheless, they left readers with a series of nutritional and behavioral prescriptions revealing an unyielding confidence that FAFH per se continues to supply the United States with an increasing number of overweight and unhealthy children.
For example, the report urges fast food consumers to “tailor away-from-home meals to make them as healthful as possible,” and to “control food and beverage portions” by sharing, ordering half-portions, or taking the excesses home. It finally concludes with a plea to “reduce reliance on away-from-home food.” But never does the CDC’s report consider whether fast food consumption might be a mere marker for a more instrumental set of bad nutritional attitudes and habits.
In 2010, four researchers at the Economic Research Service of the U.S. Department of Agriculture published a similar, but more involved report, “How Food Away From Home Affects Children’s Diet Quality” (Mancino 2010). Led by Lisa Mancino, the group purportedly set out, first, to test the now-popular childhood obesity-FAFH hypothesis and, second, to help inform public policy prevention strategies.
Mancino’s analysis was based on data from the 2003-2004 National Health and Nutrition Examination Survey and the 1994-1996 Continuing Survey of Food Intakes by Individuals. Children ages six to eighteen were included, and FAFH was defined as all commercially prepared food—featuring fast food but not food from schools. Results were based on both relative caloric intake and diet quality, as measured by the 2005 Healthy Eating Index. Mancino also attempted to control for the impacts of sugar-sweetened beverages and certain personal characteristics such as food access and preferences.
The government’s findings were striking, of course, but far from unexpected. For all children, Mancino discovered, each FAFH meal added 65 total calories and lowered diet quality scores by four percent compared to meals prepared at home. Older children between thirteen and eighteen fared significantly worse, receiving 107 additional calories.
Mancino’s report provides Americans with yet another remarkable set of statistics that might well induce effective behavior change assuming two premises: first, that fast food actually causes childhood obesity and, second, that the target population is open to such adjustment. But do Mancino’s results truly speak to the foundational issue of causation?
She and other officials at the U.S. Department of Agriculture certainly seem to think so. Her study’s findings, they contend, not only “support the contention that increased consumption of FAFH is a contributing factor in the current epidemic of childhood obesity,” but also “strengthen() the argument that there is a causal relationship between FAFH and increased caloric consumption and decreased dietary quality.”
Again, the possible effects of other food—even food from the most ubiquitous source available to children—were never discussed. But isn’t it far easier to intuit, for example, that American kids are getting fat and consuming fast food as a result of nutritional habits and attitudes established at home?
A very similar question occurred quite recently to three nutrition scientists led by Barry Popkin at the University of North Carolina at Chapel Hill. In a new study supported by both the Robert Wood Johnson Foundation and the National Institutes of Health, Popkin’s group attempted to distinguish and compare the independent associations between childhood obesity and either fast food consumption or the remainder of dietary intake (Poti 2014).
Popkin’s cross-sectional analysis included 4466 children ages two to eighteen who participated in the 2007-2010 National Health and Nutrition Examination Survey. In terms of fast food, the young subjects were classified as either non-consumers, low-consumers (0.1-30% of energy), or high-consumers (>30%). Popkin’s group also attempted to control for various potential counfounders, including physical activity levels, sex, age, race-ethnicity, and parental income and education.
The authors first note that previous research has focused intensely on fast food as the key contributor to the rising incidence of childhood obesity. But prior studies, they argue, tended to “control for, rather than explore, the differences between fast food consumers and nonconsumers.” Indeed, the mere possibility that fast food might not be directly associated with childhood obesity, they agree, had to that point never been tested.
So Popkin set out to address the problem anew by incorporating and analyzing food choices made outside the fast food restaurant. In other words, to test his hypothesis that a nutritionally imprudent at-home diet actually associates more robustly with overweight than fast food consumption per se, Popkin contrasted the at-home dietary patterns of fast food non-consumers, low-consumers, and high-consumers.
After examining remainder of dietary intake, then, the authors discovered that the children had clustered into two distinct groups. Roughly half consumed a typical “Western diet,” characterized by higher intakes of sugar-sweetened beverages, salty snacks, high-fat sandwiches, and candy; while the others ingested a “Prudent diet,” marked by higher intakes of milk, fruit, and low-fat mixed dishes.
Popkin’s results defied received institutional wisdom. First, both fast food high- and low-consumers were significantly more likely to consume a Western at-home diet than non-consumers (63.4 %, 54.2%, and 43.9%, respectively). Second, children who combined both high-fast food consumption and a Western diet showed significantly higher prevalence of overweight or obesity than Prudent non-consumers (40.4% and 28.0%, respectively).
Absent consideration of remainder of dietary intake, high-fast food consumption was significantly associated with a higher incidence of overweight. But that association, the authors emphasize, was “attenuated and nonsignificant after adjustment for the remainder of diet.” On the other hand, “consuming a Western dietary pattern . . . was significantly associated with a higher prevalence of overweight/obesity after control for fast food intake.”
In sum, when both eating behaviors were considered, “the remainder of diet, but not fast food per se, was associated with overweight/obesity.” In previous obesity studies, Popkin adds—including the 2010 analysis conducted by Mancino and other officials at the U.S. Department of Agriculture—“(a)ssociations between fast food intake and these health outcomes were overestimated.”
The authors close with an aspirational missive to American policy-makers. These new findings, they warn, also “suggest that the effect of public health efforts targeted at fast food restaurants may also be overestimated” and “not sufficient to reduce childhood obesity if the remainder of the diet is not also addressed.”
As always, the research must continue. Nevertheless, common sense should inform us all that childhood obesity originates, matures, and proliferates in the home. Children don’t live in fast food restaurants, after all, and restauranteers are not responsible for the teaching of lifestyle values, attitudes, and habits to our kids. No family has ever been forced to consume ridiculously inappropriate “foods,” or to sit in front of the television set to view obviously manipulative advertisements. Plainly, no aspect of fast food will ever be the real issue.
On the other hand, should the U.S. government continue to intercede between childhood obesity and its genesis, it should do so efficiently and scrupulously. And if any government official genuinely desires to affect childhood obesity, then he or she will surely speak the entire truth to the one true political power (and to the party that needs to hear it most)—that is, the American majority.
Recent studies and popular media reports alleging a decline in U.S. childhood obesity may have been mistaken. Instead, new research finds that all classes of childhood obesity, especially severe obesity, have increased in the last 14 years. Skinner, A.C. and Skelton, J.A. 2014. Prevalence and trends in obesity and severe obesity among children in the United States, 1999-2012. JAMA Pediatr. Published online April 7, 2014. doi:10.1001/jamapediatrics.2014.21.
Incorporating Away-From-Home Food into a Healthy Eating Plan. Research to Practice Series, No. 6. National Center for Chronic Disease Prevention and Health Promotion Division of Nutrition, Physical Activity, and Obesity. http://www.cdc.gov/needphp/dnpa/nutrition/pdf.r2p_away_from_home_food.pdf (last accessed on April 2, 2014).
Mancino, L., Todd, J., Guthrie, J., and Lin, B-H. 2010. How food away from home affects children’s diet quality. Washington, D.C.: U.S. Department of Agriculture, Economic Research Service. (Economic Research Report No. 104).
Poti, J.M., Duffy, K.J., and Popkin, B.M. 2014. The association between fast food consumption with poor dietary outcomes and obesity among children: is it the fast food or the remainder of diet? Am. J. Clin. Nutr. 99: 162-171.
Michael L. Power and Jay Schulkin, The Evolution of Obesity (Johns Hopkins Press, 2009.