I’m taking some nutrition courses these days, and as part of my coursework, I’ve been learning about food availability or food disappearance data. These are data that reflect a country’s total annual food production, imports, and initial stock of food, subtracting out exports, non-food uses of these items, and end-point stockpiles. As such, they overestimate what people eat (because they include in the total food that was spoiled and thrown out, for example), but give a rough idea of people’s food consumption and trends over time. These data have been reliably collected in the U.S. for more than a century (although not necessarily for all foods), so they provide an interesting snapshot of what we are eating. The below information I collected for a class assignment, but I thought it was so interesting it deserved a wider audience and am sharing it here as well.
Since food availability data are available for many foods going back decades, we can observe whether changes in food consumption in the U.S. over time map onto changes in other health indicators. My interest here of course is in obesity, and what people breathlessly call the “obesity epidemic.”
Take a look at this image, which is from the National Institute of Diabetes and Kidney Disease’s page on Overweight and Obesity Statistics (http://www.niddk.nih.gov/health-information/health-statistics/Pages/overweight-obesity-statistics.aspx):
The green-gray area at the bottom of the graph is the percentage of U.S. adults who were classified as overweight in that year; the dark green is the percentage obese, and the gray at the top is the percentage of extremely obese people. I’m a little confused by the graph in that BMI definitions for overweight, obese, etc., changed in the mid-1990s, and I don’t know whether this graph adjusts for that or uses the earlier or later definitions. But for now let’s just assume that the definition of these categories remained constant over time.
What’s interesting about this graph is first of all that there is no epidemic of overweight. The percentage of people in the overweight category has stayed roughly steady over time. (That is interesting in and of itself. Why don’t *both* overweight and obesity increase during this time?) But they don’t: Only obesity and extreme obesity have increased. It’s also interesting to observe that that change happened suddenly. Somewhere between the late 1970s and 2000 is when essentially all of the change occurred, and then it leveled off.
If you believe diet causes obesity (and I’m far from convinced on this point, but many people do believe this), then you should be interested in what on earth might have dramatically changed in Americans’ diets between 1970 and 2000 to explain the change. The change — whatever it was — should have happened at or just before that time, and then leveled off to produce a pattern similar to what we see on the graph.
Food disappearance data should be one of the best sources to examine this question.
Before we look at the data, though: Take a guess. What do you think has changed in Americans’ diets since 1970 that explains the increase in obesity during that time? Really, write it down. Keep yourself honest. Now, let’s take a look:
This article (http://ajcn.nutrition.org/content/91/5/1530S.full; Barnard, 2010) provides some useful tables summarizing food availability data since 1909. If you want to explain the “obesity epidemic” using diet, you should be looking for foods that saw big increases or decreases between 1970 and 2007.
Here’s one relevant table from that article:
Availability of major food commodities in the United States, 1909–20071
|Meat, total2||56.3||44.6||80.7 (48.3)3||91.2 (54.4)|
|Red meat||46.2||35.0||60.0 (37.3)||50.3 (31.2)|
|Poultry||5.1||4.9||15.4 (9.1)||33.5 (19.8)|
|Fish and shellfish||5.0||4.8||5.3 (1.9)||7.4 (3.4)|
|Eggs (individual eggs/y)|
|Eggs, fresh and processed||284.0||270.9||302.2 (238.9)||245.1 (189.6)|
|Dairy products (kg/y)|
|Fluid milk, total||133.7||129.1||122.3 (86.2)||81.0 (57.0)|
|Whole milk (plain and flavored)||105.0||109.5||99.6 (70.1)||25.0 (17.5)|
|Low-fat and skim milk||28.7||19.7||22.7 (13.3)||56.0 (35.0)|
|Cream||5.6||5.7||1.8 (2.3)||3.8 (0.0)|
|Butter||8.1||8.0||2.5 (2.0)||2.1 (1.7)|
|Cheese, whole and part-skim milk||1.7||2.4||5.2 (4.0)||14.9 (11.2)|
|Cheese, cottage||0.3||0.6||2.3 (1.6)||1.2 (0.8)|
|Frozen dairy products||0.7||3.8||13.0 (9.1)||11.5 (8.0)|
|Evaporated and condensed milk||2.8||8.5||5.5 (3.8)||3.5 (2.5)|
|Dry milk||NA||0.8||2.6 (2.5)||1.5 (1.4)|
|Added fats and oils (kg/y)|
|Added fats and oils, total||16.1||21.8||25.3 (17.5)||39.4 (25.9)|
|Butter||8.1||8.0||2.5 (2.0)||2.1 (1.7)|
|Margarine||0.6||1.4||4.9 (3.9)||2.0 (1.6)|
|Lard||3.1||4.4||2.0 (1.0)||0.7 (0.4)|
|Edible tallow||NA||NA||0.2 (0.1)4||1.3 (0.7)|
|Shortening||3.6||5.5||7.9 (5.3)||9.5 (6.4)|
|Salad and cooking oils||NA||NA||7.0 (4.4)||22.8 (14.5)|
|Other fats and oils||0.7||2.7||1.0 (1.0)||0.8 (0.7)|
|Peanuts and tree nuts (kg/y)|
|Peanuts||NA||NA||2.5 (2.1)||2.9 (2.4)|
|Tree nuts||NA||NA||0.8 (0.7)||1.5 (1.3)|
|Fruit and fruit juices (kg/y)|
|Fruit and fruit juices, total||NA||NA||79.3 (49.3)||96.8 (60.2)|
|Fresh fruit||NA||NA||43.7 (19.2)||54.4 (24.5)|
|Fruit juice||NA||NA||22.0 (18.5)||32.5 (27.5)|
|Other processed fruit5|
|Canned||NA||NA||10.6 (9.0)||6.4 (5.4)|
|Frozen||NA||NA||1.5 (1.3)||2.1 (1.8)|
|Dried||NA||NA||1.2 (1.0)||1.0 (0.8)|
|Other process||NA||NA||0.3 (0.2)||0.4 (0.3)|
|Vegetables, total||NA||NA||103.4 (67.7)||130.0 (80.3)|
|Fresh||NA||NA||65.6 (37.3)||85.0 (45.1)|
|Canned||NA||NA||22.9 (19.3)||21.3 (18.0)|
|Frozen||NA||NA||9.8 (6.8)||17.7 (12.0)|
|Flour and cereal products||136.4||92.7||62.0 (43.2)||89.5 (62.6)|
|Caloric sweeteners (kg/y)|
|Total caloric sweeteners||NA||NA||54.1 (38.5)||62.0 (44.1)|
|Cane and beet sugar||NA||NA||46.3 (33.0)||28.2 (20.0)|
|Corn-based sweeteners||NA||NA||7.2 (5.1)||33.1 (23.6)|
|Syrups and honey||NA||NA||0.7 (0.5)||0.6 (0.5)|
United States per capita beverage availability, 1970–20071
|Carbonated soft drinks||127.32||184.8|
In looking at the table, there were reasonably big increases in the following foods between 1970 and 2007: poultry, low fat and skim milk, cheese, salad and cooking oils, whole fruit and fruit juices, vegetables (mainly fresh and frozen), grains, corn syrup, and non-milk beverages, especially soda, water, and beer and wine. (The article notes something the table doesn’t — most of that increase in soda is an increase in diet soda, NOT sweetened soda).
Big decreases happened with milk, red meat, eggs, and sugar.
So, what do you make of that? Which of those changes do you think most plausibly relate to the change in obesity, and why? (Or do you think none of these factors explain it, and why?)
My own take is that either these changes do not explain the increase in obesity at all (they seem to be mostly relatively small changes), or if a change is partially responsible, then these are my votes for which foods are plausible:
- The increase in poultry might be responsible, if antibiotic residues in poultry are causing changes in the human gut microbiome (e.g., see Riley, Raphael & Faerstein, 2013)
- Perhaps high fructose corn syrup
- Perhaps diet soda, particularly since diet soda consumption may be a marker for dietary restriction, which may lead to weight gain
- Maybe the increase in grains or cooking oils?
I’d be curious to hear your take…..
(And here are the references for this post:
Barnard, N. D. (2010). Trends in food availability, 1909–2007. The American journal of clinical nutrition, 91(5), 1530S-1536S.
Riley, L. W., Raphael, E., & Faerstein, E. (2013). Obesity in the United States–dysbiosis from exposure to low-dose antibiotics?. Frontiers in public health, 1.)