Category Archives: Diet & Nutrition

Guess What: Food Prices Still Near All-Time Highs

The FAO Food Price Index (FPI) remains at near record-highs, and this at a time when record droughts and calamitous famine threaten the Horn of Africa. Using the latest data from the FAO FPI page, I plot here the FPI time series from 1990-2011.


World food prices are high and have remained so since the beginning of this year, though there have been some pretty dramatic swings between 2008 and now.  There is some argument that the real problem for poverty alleviation is actually price volatility and not high prices per se.  However, a recent paper in Foreign Affairs by Barrett and Bellemare argues that the problem for the world's poor is really high prices (a more complete working paper can be found here). I find their arguments quite persuasive. Among these, the authors wryly note "Perhaps not coincidentally, [commentators' and politicians'] emphasis on tempering price volatility favors the same large farmers who already enjoy tremendous financial support from G-20 governments."

Jennifer Burney Lecture

I've spent the better part of the day editing web pages as I prepare to teach two courses this spring. Given that I've more-or-less wasted the day with necessary but not especially intellectually rewarding tasks, I thought that I would take a moment to post something really important and scientifically interesting. Jennifer Burney, of Stanford's Program in Food Security and the Environment, gave a talk entitled "Food's Footprint: Agriculture and Climate Change" at Oregon State's Food for Thought Series. We've known Jen for a long time now.  If memory serves me correctly, she was in my wife Libra's section of the American Civil War at Harvard in Fall of 1995. Later she was a student in Mather House, where we were resident tutors from 1997-2001. She went on to do a Ph.D. in physics at Stanford and then moved into a post-doctoral fellowship at FSE.

Jen and all the folks at FSE are doing great and fundamental work.  In this talk, she presents results that may seem somewhat counter-intuitive. Namely, she shows that the agricultural intensification attendant to the Green Revolution has been good for global carbon budgets -- and feeding hungry people.  It's all about counterfactuals. I am looking forward to reading this work since some of these counterfactuals depend critically on demographic assumptions.

As she says in the talk, just because the results suggest that intensive agriculture is good from a global warming perspective, doesn't take Big Agriculture off the hook. There are items that their models don't incorporate (but could in principle) and they don't consider anything other than carbon budgets.  It would be nice to think of a way of uniting all the costs and benefits of intensification in a single framework.

This is very important stuff and the work highlights the complexities of population, environment, and food production. I look forward to seeing more work from Jen and her collaborators at FSE.

Food Prices Continue to Rise

Newly released data by FAO show that food prices continued to rise, up 3.4% from the last month of 2010. This is yet another record high. Here is a plot based on the FAO data (click to enlarge):


An article in today's New York Times attributes much of the rise in price to uncertainty over coming harvests. It also notes the four main factors that contribute to increased price: weather, higher demand (from larger population size and greater demand for meat and dairy), smaller yields, and the diversion of food crops to biofuels.

Worrying Trends

The UN's Food and Agriculture Organization's food price index is at an all-time high, meaning that the food security of millions of people is in jeopardy. In the plot below (click to enlarge), we can see that the FPI currently just exceeds its previous high in June of 2008, when riots over food shortages were widespread. This is something to keep an eye on for the new year.


Functional Training for the Army

A very interesting piece in the New York Times today details how the Army is changing its conditioning program. The impetus for this policy change is twofold.  First, functional training should better prepare soldiers for the physical challenges entailed in their duties. This seems like a great reason to overhaul the Army's physical fitness program. The second is the more depressing reason.  Not surprisingly, more recruits today are more obese, weak, and generally out-of-shape than they were in previous generations. The article cites a recent report written by a commission of retired generals, admirals, and other civilian military leaders entitled "Too Fat to Fight." The authors of this report note that the rejection rate of potential recruits on the grounds of obesity increased 70% from 1995-2008. Perhaps the most shocking statistic is that, when all the major disqualifiers for military service are combined, 75% of young people age 17-24 would be unable to join the military even if they wanted to. The generals and admirals see the current epidemic of obesity in the US as a threat to national security. The key proposed solution to this crisis is a call for investment in healthy food in our nation's schools:

We are calling on Congress to pass new child nutrition legislation that would (a) get the junk food out of our schools; (b) support increased funding to improve nutritional standards and the quality of meals served in schools; and (c) provide more children access to effective programs that cut obesity.

This is a tall order.  Current political discourse in the United States does not seem to favor investment in the future.  I'm sure that more than one demagogue in Congress would label such policies as "socialist" (the disparaging term apparently favored for any policy that seeks to invest in the human capital of our nation),  despite the fact that the recommendations come from a cadre of eminent retired military officers.

School "nutrition" programs are in a pretty sorry state of affairs nationwide.  I am reminded of the Simpsons Treehouse of Horror V, in which Doris the lunch lady says to to principal Skinner, "Don't bitch to me, boss man. Thanks to the latest budget cuts, I'm down to using Grade F meat!" (the ingredients of which are "Mostly circus animals, some filler"). We pack our kids' lunches because we don't want them eating the food available to them at school -- and we are lucky enough to live in an affluent school district!

A point not made in the "Too Fat to Fight" report is the decline in physical education opportunities.  A fact sheet put together by the American Heart Association notes that "Only 3.8% of elementary schools, 7.9% of middle schools and 2.1% of high schools provide daily physical education or its equivalent for the entire school year. Twenty-two percent of schools do not require students to take any physical education at all." And, of course, as budgets get tighter, both school nutrition and physical education programs become attractive targets for cutting back (along with just about any other type of enrichment that doesn't directly translate into a standardized test score).

I hope we can find a way to make the necessary investments in the future.  Reducing childhood obesity now will save us healthcare dollars in the long run and leave us better prepared for the many challenges -- military and otherwise -- of the twenty-first century.

Most Cited Papers in Current Anthropology

A friend sent me a link the other day to the top 20 most cited articles in the journal, Current Anthropology. Much to my delight, I found that a paper that I co-authored is the #7 all-time citation leader and a paper co-authored by my Stanford colleague Rebecca Bird is the #19. As I walked over to Coupa café this morning to get coffee, I realized that I also made a small contribution to the #1 on this list, Leslie Aiello and Peter Wheeler's paper on the Expensive Tissue Hypothesis.  At the time the manuscript was first circulated, I was a graduate student obsessed with brains, energetics, and scaling in human evolution. My advisor, Richard Wrangham, was asked to comment on the manuscript and he asked me if, given my obsessions, I might have something to say. Needless to say, I did. Having just read our comment, I think it stands pretty well (if I do say so): (1) basal metabolic rate (BMR) is not really a constraint and (2) what are the implications for allometric scaling of different organs with respect to body mass?  Most of the expensive organs scale isometrically (that is, with a scaling exponent of one) but the brain, of course, is a big exception. It scales with an exponent closer to 3/4. Because guts and brains scale differently with increasing body mass, perhaps larger brains could be maintained by dietary compensation?

My colleague Herman Pontzer has some very interesting things to say about energetics and constraints and I'm really looking forward to some forthcoming work of his on this topic.  In a paper in PNAS, he recently showed that, contrary to the expectations of a naïve trade-off model, mammals with larger home ranges actually have greater lifetime fertility and greater total offspring mass.  We have a lot to learn about trade-offs, both physiological and economic, and their role in shaping human behavior and life histories.

To Serve Man

So there I was. 23 hundred hours, New Year's Eve 2008 at my in-laws' in Corvallis, Oregon. Kids asleep in the other room. Spouse headed in the same direction. Insomniac from lack of activity and feelings of general physical displacement. Not much prospect for a party or other New Year's antics. Sounds like the perfect set-up for a Twilight Zone marathon, no? I think that I managed to make it through about 8 episodes in the wee hours of the first day of 2009. I wonder what that augers for the new year?

One of the episodes I managed to watch was "To Serve Man" (viewable freely in its entirety here). It's your standard aliens land, aliens altruistically transfer advanced technology, aliens solve all of humanity's problems, aliens turn out to have ulterior motives, aliens plan to eat all of humanity kind of plots. You see, the Kanamits have come to Earth to bring humanity back to their home world to eat them. The book that the Kanamits spokesman leaves in the United Nations (the big tease...) turns out to be a cookbook, a fact that the crack cryptographic team headed by protagonist Michael Chambers discovers too late. Chambers is already boarding the ship bound for his vacation getaway to the Kanamits' home world when the real brains of his outfit, the beautiful Pat, comes running to inform him (and, maddeningly for humanity, only him) of the horrible news. He's shipping off to get eaten. Get it? "Serve" as in provide assistance vs. "serve" as in provide a meal?

Toward the end of the episode, Michael Chambers, says in soliloquy that the recollections he has just shared represent the life cycle of Man "from dust to dessert." He comments that every person will ultimately share his fate (i.e., being served): "Sooner or later, we'll all of us be on the menu." This is what got me. Surely not. This doesn't seem like very good natural resource management on the part of the Kanamits.

The classical theory of natural resource management suggests that there should be a maximally sustainable yield for farmed humans. We will assume that human population growth can be written in terms of its current size and some function of size \dot{N}= N f(N), where \dot{N} indicates the derivative of population size with respect to time t. For simplicity's sake, let's assume that the effect of density on the human growth rate is linear such that f(N) = r(1 - N/K), where r is the intrinsic rate of natural increase K is the carrying capacity (i.e., the maximum number of people the Earth could potentially support).

Now, I should note that this is a purely hypothetical exercise meant simply to illustrate basic concepts. In any real Soylent Green like future where we are faced with fattening Peter to save Paul, we would need a much more sophisticated population model. Among other things, the idea of a carrying capacity for humanity is a maddeningly elusive one. The eminent demographer Joel Cohen has written a whole book on the matter and comes up with no particularly satisfying answer to the seemingly basic question of How Many People Can The Earth Support?

For argument's sake, let's just say that the maximum intrinsic rate of increase is r=0.04 (4% annual growth, which is high, but remember, humanity has just received this remarkable technology transfer) and the carrying capacity is K=10^{10} (i.e., 10 billion). Population growth changes with population size. We can plot the incremental increase (recruitment) as a function of population size. The maximum point of this so-called recruitment curve, where d\dot{N}/dN=0 is the MSY.

For the simple linear model of density-dependence (i.e., the logistic growth equation) and with no time preferences on the part of the Kanamits, the maximum sustainable yield (MSY) occurs at MSY=K/2 or 5 billion souls. So, you can now understand my dismay at 0200 (or whatever it was) on the first day of 2009. Why would everyone necessarily meet the fate of Michael Chambers? Under optimal harvest management, only half should be harvested. I can think of at least three explanations for this conundrum:

  1. Michael Chambers is either misinformed (he was a cryptographer, after all, and not a wildlife manager) or was exaggerating for dramatic effect.
  2. The Kanamits, while advanced in the physical sciences, had not developed an adequate theory of natural resource management or population dynamics more generally. Perhaps this is why they needed to come all the way to Earth to acquire their dessert?
  3. Perhaps the Kanamits actually had a very sophisticated understanding of population biology and realized that the human intrinsic rate of increase was less than the prevailing discount rate. Under these conditions, the optimal resource-management strategy is liquidation of the stock.

I'm leaning toward explanation #3. That was an awful long way to come, after all.

Sobering thoughts with which to commence the new year.

Biofuels and Water Use

An opinion piece in the IHT this morning raises the important point that stepped up biofuel production may tax already strained world fresh water supplies.  Peter Brabeck-Letmathe, chairman and former chief executive of Nestlé, suggests that if world biofuel production targets are met, water withdrawals for agriculture can increase by as much as one-third.  Brabeck-Letmathe writes,

Seventy percent of all water withdrawal is already used in agriculture, and while all such activity requires water, growing enough soy or corn to create biofuels is especially water-intensive. For example, to produce just one gallon of diesel fuel up to 9,000 gallons of water are required. Up to 4,000 gallons are needed to produce enough corn for the same amount of ethanol. By way of contrast, producing enough food to meet the caloric needs of one person for one day in, for example, Tunisia or Egypt requires about 666 gallons of water, and twice as much in California (caloric needs and intakes vary widely from region to region due to dietary customs).

This is bad news considering that it is projected that by 2035, one third of the world (over three billion people) will be facing severe water stress.  Even without the increased water pressure of extensive biofuel production, water usage will need to increase substantially in order to feed the world by the middle of the century.

These are the sort of issues that we need to take seriously before plunging headlong into a world where we grow the fuel that drives American (and, increasingly, Chinese) SUVs.