How Much Fatter are We?

I am working on a presentation I will give later in the month at the University of Alabama Medical School on the economics of obesity.  To put things in context, I wanted a graph showing the average weight of US men and women over the past 40 or so years.  If you think it would be easy to find this information on the web, you'd be wrong.  

There are lots of studies reporting the percent obese or reporting the mean BMI for a couple years, but the CDC, for some reason, hasn't complied a simple data set that lets you compare in the same units (their publications sometimes report means, sometimes medians, sometimes BMI, sometimes weight in lbs) for consistent age ranges.  After several hours work, I finally cobbled together the graph below showing the average weight (in lbs) of men and women from about 1960 to 2010 for people aged 40-49 (if you want to check me, the data was obtained from the publications here, here, and here, all of which rely on National Health and Nutrition Examination (NHANES) Survey).

Is it what you expected?  From about 1960 to today (or at least the latest comparable data I could find), the average weight of men aged 40-49 has increased 31.5 lbs.  For women, the number is 27.2 lbs.  In the past 10 years, the average weight of men aged 40-49 has increased 4.6 lbs.  For 40-49 year old women, weight actually fell 0.2 lbs over this time period.  In the last four years, the average weight of men in this age rage actually went down 1.7 lbs and the average weight of women fell 3.3 lbs.  

It is also worth mentioning that the average 40-49 year old male is today 1.3 inches taller than he was in 1960.  The average women is a full inch taller as well.

Whether these changes in weight are large or small are a subjective judgement call.  I will only point out that the average 40-49 year old women today weights about the same as the average 40-49 year old man from 1960.

Better Hope Your Child Isn't Obese

Jerri Gray may spend the next fifteen years of her life in a South Carolina prison.  She is not a drug dealer or a serial rapist.  She has not robbed anyone or  committed grand theft  auto—she simply has an obese son

Those are the opening sentences of this article by Elizabeth Ralston in the Seton Hall Law Review entitled KinderLARDen Cop: Why States Must Stop Policing Parents of Obese Children

Is it Time to Reconsider High BMI as Dangerous?

An article in the most recent issue of the Journal of the American Medical Association by Flegal et al. presents some serious evidence to question the hysteria over the rise in obesity (see also the commentaries here and here and here).

Apparently being "normal" weight isn't optimal if your goal is to live longest.  In fact, being a bit overweight (and even a bit obese) might add a few years to life.  As Jacob Sullum over at Reason suggests, perhaps we aught to re-define what is meant by "normal" weight given that the majority of people have BMIs that are beyond the "normal" cagetory.  Not only do people weigh more than "normal" - their weights are such that they are living longer too.  

I've received quite a lot of flack from various folks over the comments in my TEDx talk a couple months back, in which I argued that the rise in the rate of obesity had declined or even stopped.  Yet, when I provide incontrovertible evidence to support my statements (see here or here), I'm often met with dismay, disbelief, and even claims of dishonesty.  This is not to mention the fact that heart disease and other such ailments have fallen dramatically.   

We have a well entrenched narrative that: 1) obesity is uncontrollably rising and 2) something must be done because obesity is killing people and increasing medical costs.  The cites in my TEDx talk disputes the first argument.  The results in the current issue of JAMA dispute the second.  There are those who derive their meaning (and power) by pushing for public health interventions to combat obesity.  My hope is that that the reasonable scientists in the group will rationally update their priors with this new information.    

Obesity Links

• Obesity rates are declining among low income children

• The Economist on obesity (they offer a good summary of the ineffectiveness of most public policies to combat obesity, but they seem to uncritically accept the premise that obesity is an externality)

• The Blondie cartoon strip takes on Bloomberg's soda ban

Efficacy of Fat Taxes and Thin Subsidies

Science News reported the following results from a recent study:

Taxes on soft drinks and foods high in saturated fats and subsidies for fruit and vegetables could lead to beneficial dietary changes and potentially improve health, according to a study by experts from New Zealand published in this week's PLOS Medicine.

and

The authors say: "Based on modelling studies, taxes on carbonated drinks and saturated fat and subsidies on fruits and vegetables are associated with beneficial dietary change, with the potential for improved health. "

My first reaction was "duh."  Clearly if you raise prices of (say sugar or fat) high enough, you will get people to eat less.  In fact, one way researchers often model a ban on a substance is by simulating what happens when the price gets high enough that no one buys the product.  

Thus, the key question isn't whether one can change consumption and nutrient intake with sufficiently high taxes or subsidies.  The better questions are by how much? and at what cost?  An even better question still: where is the market failure that would justify the tax or subsidy?  The answer to that last question is actually much less obvious than most public health professionals presume (see here or here).

On the former question of how much?, let's turn to the original study mentioned at the first of this post.  The study is actually a literature review, pulling together the findings of previously published papers (including one that I co-authored).  Below is a graph showing some of the key results from different studies simulating how much change in consumption (or energy intake) would occur from a change in the price of a good. Pay attention to the scale of the vertical axis.  My take (see the middle chart) is that it would take very large price changes to get energy consumption to change by much (a 20-40% increase in price results in a 0.2-0.4% reduction in calories consumed).  

Stated differently, these sorts of policies are likely very costly in achieving the desired health outcomes.  Moreover, we must ask why - if these health changes are really so inexpensive and beneficial - people are not already voluntarily making them?