Sunday, November 22, 2015

Fat, Added Fat, and Obesity in America

In the last post, we saw that carbohydrate and particularly sugar intake have been declining in the US since 1999, even as our obesity rate has continued to climb.

In this post, let's look at another putative driver of obesity: our fat intake, and especially our intake of added fats like seed oils, butter, and olive oil.  Like the graphs in the last post, the data underlying the following graphs come from USDA food disappearance records (not self-reported), and NHANES survey data (1, 2).  Also like the last post, the graph of total fat intake is not adjusted for waste (non-eaten food), while the graph of added fat intake is*.  As a consequence, the figures for total carbohydrate and total fat intake are higher than actual intakes, but still good for illustrating trends.

Here we go.  First, total fat:

Monday, November 16, 2015

Carbohydrate, Sugar, and Obesity in America

We like explanations that are simple, easy to understand, and explain everything.  One example of this is the idea that eating carbohydrate, or sugar, is the primary cause of obesity.  This lets us point our finger at something concrete and change our behavior accordingly.  And it's true enough that it has practical value.  But the world around us often turns out to be more complex than we'd like it to be.

The CDC recently released its latest data on the prevalence of obesity in the US, spanning the years 2013-2014 (1).  These data come from its periodic National Health and Nutrition Examination Surveys (NHANES).  Contrary to what many of us had hoped for after a slight decline in obesity in the last survey, the prevalence has once again increased.  Today, roughly 38 percent of US adults have obesity.  As a nation, we're continuing to gain fat, which is extremely concerning.

I decided to examine the relationship between obesity prevalence and our intake of carbohydrate and sugar over the years.  The food intake data come from the USDA's Economic Research Service (2).  For some reason, the data on carbohydrate don't extend beyond 2010.  This probably relates to funding cuts at the USDA*.

Let's have a look at the data for carbohydrate: