In this three-part series, I will be evaluating some of the proposed dietary drivers of the obesity epidemic in the United States.
I decided to create this series to address claims that are made on the my forum, which are, quite frankly, at odds with the evidence. I hope that this blog post will contribute to putting some of these claims to rest.
In the first part of this series, I will be addressing a popular theory: that the obesity epidemic is driven by increasing consumption of wheat.
This claim is evidently at odds with the evidence–a huge amount of evidence. Here’s a few pieces of that evidence.
- Wheat consumption has decreased over the past fifteen years (United States Department of Agriculture):
- Yet, the percentage of obese adults has gone from 30.5 to 37.7% in the same period of time (United States Center for Disease Control):
It therefore follows that over the last 15 years, the consumption of wheat and the rise of obesity have been strongly INVERSELY correlated: wheat consumption has consistently gone down, while obesity has consistently gone up.
- But wait, there’s more. This decline in wheat consumption is, from historical perspective, even more marked (United States Department of Agriculture):
From 1935 levels, Americans’ consumption of wheat is down nearly 40 pounds per person per year.
- Yet, while the level of wheat consumption in the 1930s was higher than its peak in the ’90s, and much higher than that today, average BMI (and levels of obesity) was lower in the ’30s (Centre for Economic Policy Research, VOXEU):
(The highest line marks the 90th percentile, the lowest lowest line marks the 10th percentile, with all gradations in between.)
In other words, the historical record on obesity shows a trend in the opposite direction of this decrease in wheat consumption.
- To drive the point home, here is a graph of the rate of change in BMI, also charted in deciles:
Perhaps the most remarkable feature of this graph is the inflection point that occurs between 1945 and 1950, just following World War 2, when the rate of increase in BMI among deciles–especially the upper 2-4 deciles–begins to spread markedly, and the rate of increase in obesity accelerates dramatically. Relevant to the theory of wheat consumption-driven obesity epidemic, according to the information presented two graphs back, this inflection point occurs at precisely the same moment when wheat consumption per capita in the U.S. begins a marked, 3-decade-long decline.
So again, we see an inverse correlation between wheat consumption and obesity.
- There’s more evidence to contradict the case against wheat (at least in terms of the obesity epidemic). How does the United States compare to other countries? As the most obese developed country in the world, does the United States have the highest consumption, per capita, of wheat? Is it even in the upper tier of wheat consumption?
The United States, the most obese developed country in the world, actually has relatively low levels of wheat consumption, at least when compared to many other developed countries. Data from the World Bank:
|Australia||308.04 thousand metric tons||2004|
|Turkey||254.32 thousand metric tons||2004|
|Russia||246.79 thousand metric tons||2004|
|Canada||240.66 thousand metric tons||2004|
|Morocco||207.66 thousand metric tons||2004|
|Ukraine||204.95 thousand metric tons||2004|
|Algeria||195.75 thousand metric tons||2004|
|Iran||190.36 thousand metric tons||2004|
|Egypt||179.91 thousand metric tons||2004|
|Pakistan||120.85 thousand metric tons||2004|
|United States||113.4 thousand metric tons||2004|
|China||80.63 thousand metric tons||2004|
|India||62.13 thousand metric tons||2004|
|Brazil||54.07 thousand metric tons||2004|
|Japan||47.28 thousand metric tons||2004|