Water for the Pima

A few months ago, I published a post about the Pima Indians (Akimel O'odham) of Arizona. The Pima are one of the most heart-wrenching examples of the disease of civilization afflicting a society after a nutrition transition. Traditionally a healthy agricultural people, they now have some of the highest rates of obesity and diabetes in the world.

The trouble all started when their irrigation waters were diverted upstream in the late 19th century. Their traditional diet of corn, beans, squash, fish, game meats and gathered plant foods became impossible. They became dependent on government food programs, which provided them with white flour, sugar, lard and canned goods. Now they are the subjects of scientific research because of their staggering health problems.

I'm happy to report that after more than 30 years of activism, lawsuits and negotiation, the Pima and neighboring tribes have reached an agreement with the federal government that will restore a portion of their original water. Of the 2 million acre-feet of water the Pima were estimated to have used since before the 16th century, the settlement will restore 653,500. An acre-foot is approximately the personal water use of one household. The settlement also provides federal funds for reconstructing old irrigation canals.

Now we will see how the Pima will use it. Will they return to an agricultural lifestyle, perhaps with the advantages of modern technology? Or will they lease the water rights for money and continue to live off Western foods? Perhaps some of both. They are definitely aware that Western food is causing their health problems, and that they could regain their health by eating traditional foods. However, white flour "fry bread", sugar and canned meat have been around for so long they are also a cultural tradition at this point. Only time will tell which path they choose.

Two Things that Get on My Nerves, Part I

The "Thrifty Gene" Hypothesis

The thrifty gene hypothesis is the darling of many obesity researchers. It was proposed in 1962 by the geneticist James V. Neel to explain the high rates of obesity in modern populations, particularly modernizing American Indians. It states that our species evolved under conditions of frequent starvation, so we're designed to store every available calorie. In today's world of food abundance, our bodies continue to be thrifty and that's why we're fat.

Obesity researchers love it because it dovetails nicely with the equally dim "calories-in, calories-out hypothesis", whereby calories alone determine body composition. You practically can't read a paper on overweight without seeing an obligatory nod to the thrifty gene hypothesis. The only problem is, it's wrong.

The assumption that hunter-gatherers and non-industrial agriculturalists lived under chronic calorie deprivation has been proven false. The anthropological evidence indicates that most hunter-gatherers had abundant food, most of the time. They did have fluctuations in energy balance, but the majority of the time they had access to more calories than they needed, just like us. Yet they were not fat.

The Kitavans are a good example. They are an agricultural society that eats virtually no grains or processed food. In Dr. Staffan Lindeberg's studies, he has determined that overweight is virtually nonexistent among them, despite an abundant food supply.

The cause of obesity is not the availability of excess calories, it's the deregulation of the bodyweight homeostasis system. We have a very sophisticated set of feedback loops that "try" to maintain a healthy weight. It's composed of hormones (insulin, leptin, etc.), certain brain regions, and many other elements, known and unknown. These feedback loops influence what the body does with calories, as well as feeding behaviors. When you throw a wrench in the gears with a lifestyle that is unnatural to the human metabolism, you deregulate the system so that it no longer maintains an appropriate "set-point".

Here's what Neel had to say about his own theory in 1982 (excerpts from Good Calories, Bad Calories):

The data on which that (rather soft) hypothesis was based has now largely collapsed.

And what does he think causes overweight in American Indians now?

The composition of the diet, and more specifically the use of highly refined carbohydrates.

RIP, thrifty gene.


For more information on bodyweight regulation, see:

Insulin Controls Your Fat
Leptin and Lectins
Thoughts on Obesity Part I
Thoughts on Obesity Part II
Body Composition

Genetics and Disease

There is a lot of confusion surrounding the role of genetics in health. It seems like every day the media have a new story about gene X or Y 'causing' obesity, diabetes or heart disease. There are some diseases that are strongly and clearly linked to a gene, such as the disease I study: spinocerebellar ataxia type 7. I do not believe that genetics are the cause of more than a slim minority of health problems however. Part of this is a semantic issue. How do you define the word 'cause'? It's a difficult question, but I'll give you an example of my reasoning and then we'll come back to it.

A classic and thoroughly studied example of genetic factors in disease can be found in the Pima indians of Arizona. Currently, this population eats a version of the American diet, high in refined and processed foods. It also has the highest prevalence of type II diabetes of any population on earth (much higher than the US average), and a very high rate of obesity. One viewpoint is that these people are genetically susceptible to obesity and diabetes, and thus their genes are the cause of their health problems.

However, if you walk across the national border to Mexico, you'll find another group of Pima indians. This population is genetically very similar to the Arizona Pima except they have low rates of obesity and diabetes. They eat a healthier, whole-foods, agriculture-based diet. Furthermore, 200 years ago, the Arizona Pima were healthy as well. So what's the cause of disease here? Strictly speaking, it's both genetics and lifestyle. Both of these factors are necessary for the health problems of the Arizona Pima. However, I think it's more helpful to think of lifestyle as the cause of disease, since that's the factor that changed.

The Pima are a useful analogy for the world in general. They are an extreme example of what has happened to many if not all modern societies. Thus, when we talk about the 'obesity gene' or the 'heart disease gene', it's misleading. It's only the 'obesity gene' in the context of a lifestyle to which we are not genetically adapted.

I do not believe that over half of paleolithic humans were overweight, or that 20% had serious blood glucose imbalances. In fact, studies of remaining populations living naturally and traditionally have shown that they are typically much healthier than industrialized humans. Yet here we are in the US, carrying the very same genes as our ancestors, sick as dogs. That's not all though: we're actually getting sicker. Obesity, diabetes, allergies and many other problems are on the rise, despite the fact that our genes haven't changed.

I conclude that genetics are only rarely the cause of disease, and that the vast majority of health problems in the US are lifestyle-related. Studies into the genetic factors that predispose us to common health problems are interesting, but they're a distraction from the real problems and the real solutions that are staring us in the face. These solutions are to promote a healthy diet, exercise, and effective stress management.