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Wednesday, June 21, 2017

The fast food-obesity myth

The fast food-obesity myth

Fast food is high on the ratings scale to explain the modern epidemic of obesity. It makes sense. These foods are high in calories, high in fat, highly palatable, cheap, available 24-7, heavily marketed to younger persons and totally convenient. Moreover, these compelling attributes of guilt are bolstered by data showing that in the last several decades, the number of fast food outlets has soared, as have the portion sizes of food they serve. Thus it is easy to understand why the term ‘fast food’ rolls so easily off the tongue of policy shapers and makers and why restrictions are called for to limit the number of fast food outlets and to make fast foods unattractive through higher taxation and consumer education. But, as Oliver Cromwell said in addressing the assembled Church of Scotland: “Gentlemen, in the bowels of Christ, I beseech thee. Think it possible you may be mistaken”. So let us turn to several recently published scientific articles on this topic.

The first of these draws on two data sets from the US[1]. The first is county-level data on obesity (BMI>30kg/m2) rates from the Center for Disease Control and the second is county-level data on both fast food restaurants (FFRs) and full service restaurants (FSRs) from the US Department of Agriculture’s economic database. It should be noted that this database lists not only large chain type FFRs and FSRs but also small local such restaurants. In all, data was available for the year 2012 involving 3138 counties across the US involving a population of 170 million. The results were clear cut and expressed thus by the authors: “Our a priori prediction that FFRs and FSRs would be positively linked to obesity prevalence was not supported”. They did find some evidence, which suggested that such establishments were more likely to be located in areas where there was a higher level of both income and education.  The authors then pint out that if that is the case, it would make commercial sense for FFRs and FSRs to be located in more affluent areas and that given the lower level of obesity with higher income and education, these outlets were thus located in lower obesity areas. The authors went on to quantify the extent to which variation in FFRs and FSRs density would explain variation in obesity, and, controlling for all variables (poverty, ethnicity, education, employment, household income, local recreational facilities and health insurance), FFR and FSR density accounted for only 0.8% of obesity.  They also calculated that FFR and FSR together contribute to about a quarter of total US caloric intake.

The second paper is based on data for 25,000+ European adults, 50 years or older drawing on a database from the project: ’Survey of Health, Ageing and Retirement in Europe’ (SHARE)[2]. The countries involved are: Denmark, Sweden, Austria, France, Germany, Switzerland, Belgium, the Netherlands, Spain, Italy and Greece. This survey measured body mass index and household food expenditure, including expenditure on ‘Food Away From Home” (FAFH). The findings are explained thus by the authors: ”Our results suggest, contrary to normative views, that away from home food expenditures negatively affect BMI and that BMI is negatively related to the percentage of the food budget spent away from home”. They go on to conclude: “Given our findings, the implication seems to be that a policy intervention related to the food away from home and obesity issue is not warranted for older Europeans. But if a policy prescription is really needed, then a policy that is directed at promoting better nutritional quality of foods for food-away-from-home might be in order.” The authors note that these data refer only to older Europeans and may not apply to younger citizens. The main findings are summarized in Figure 1 below.

Figure 1 from the second study above on the SHARE database of older Europeans

The third study is US based and draws on The Coronary Artery Risk Development in Young Adults (CARDIA) study which in this case involved 12,174 person-observations who participated in 6 examinations; 1985–2011) across four US cities (Birmingham, AL; Chicago, IL; Minneapolis, MN; Oakland, CA)[3].  The database was used to provide statistical input into a variety of models linking the percentage of neighbourhood food stores or restaurants (per total food outlets within 1 km network distance of respondent residence) with BMI (kg/m2). The models were adjusted for socio-demographic and health behaviour data and for city of residence, timing of subjects examinations, total food outlets and market-level prices. Once again the findings were clear-cut: “Neighbourhood convenience stores and fast-food restaurants were not associated with BMI in any model”.

The fourth and final study brings us away from out of home food purchases to old-fashioned home cooked meals[4]. It recognises that there is ample documentation of the gradual increase in portion size of foods served outside the home. It then asks the question: Has this also happened inside the home. The abstract is short and it is worth presenting it in total: “Since portion sizes have increased outside the home, could caloric content have increased over the years within the home? To examine this, a content analysis of common recipes in Better Homes & Gardens, the bestselling book in its genre, was compared from its first edition in 1930 to its most recent edition in 2010. Recipes were categorized into appetizers, side dishes, entrées, and desserts and analyzed for significant changes in total calories, number of servings, and calories per serving. From its first edition to its most recent edition, the total calories and calories per serving in appetizer recipes significantly increased by 51.18% and 52.5%, respectively. Furthermore, entrée recipes had a significant increase in total calories by 32.96%. As these increases have gone unnoticed for scratch cooks and their families, cookbook users should be wary of these drastic changes and the amount consumed to counteract ever-increasing weight gain”.

All of the above suggests that when there is a knee jerk policy move to curb fast food to reduce obesity, we should absolutely demand evidence. Certainly the first three studies won’t support this knee jerk reaction. The fourth is a bit of a shocker since home cooked food has been the ideal for decades. It is the Walton family shrine of all things wonderful from family home cooked meals to “Goodnight John Boy”. Sometimes such dreams are shattered. So we should focus more on the home and ask ourselves how food portion size in the home (and everywhere else of course) should be reduced. Controlling portion size was recorded by the McKinsey Global Institute as the top priority for policy action in tackling obesity. But rest assured, fast food will always be a handy whipping boy by the evidence-averse mouthpieces of dietary change. Fast food is s corporate villain but what about my local Chinese or Indian takeaway or my local fish and chip shop?

[1] Mazidi m & Speakman JR . Higher densities of fast-food and full-service restaurants are not associated with obesity prevalence. American Journal of Clinical Nutrition. May 2017. 
[2] Body Weight Outcomes and Food Expenditures Among Older Europeans: A simultaneous equation approach Andreas C. Drichoutis1, Panagiotis Lazaridis2 and Rodolfo M. Nayga, Jr. Paper prepared for presentation at the 113th EAAE Seminar “A resilient European food industry and food chain in a challenging world”, Chania, Crete, Greece, date as in: September 3 - 6, 2009
[3]. Rummo PE, Guilkey DK et al. Does unmeasured confounding influence associations between the retail food environment and body mass index over time? The Coronary Artery Risk Development in Young Adults (CARDIA) study. International Journal of Epidemiology, 2017, 1–9 doi: 10.1093/ije/dyx070
[4] Wansink B & Mukund A. Bigger Homes & Recipes: How recipe calories have increased over the years FASEB J April 2017 31:957.8

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