Humans on a Cafeteria Diet

In the 1970s, as the modern obesity epidemic was just getting started, investigators were searching for new animal models of diet-induced obesity. They tried all sorts of things, from sugar to various types of fats, but none of them caused obesity as rapidly and reproducibly as desired*. 1976, Anthony Sclafani tried something new, and disarmingly simple, which he called the "supermarket diet": he gave his rats access to a variety of palatable human foods, in addition to standard rodent chow. They immediately ignored the chow, instead gorging on the palatable food and rapidly becoming obese (1). Later renamed the "cafeteria diet", it remains the most rapid and effective way of producing dietary obesity and metabolic syndrome in rodents using solid food (2).

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A Little Tidbit

I'm gearing up for a new series of posts based on some fascinating reading I've been doing lately. I'm not going to spill the beans, but I will give you a little hint, from a paper written by Dr. Robert S. Corruccini, professor of anthropology at Southern Illinois university. I just came across this quote and it blew me away. It's so full of wisdom I can't even believe I just read it. The term "occlusion" refers to the way the upper and lower teeth come together, as in overbite or underbite.

Similar to heart disease and diabetes which are "diseases of civilization" or "Western diseases" (Trowell and Burkitt, 1981) that have attained high prevalence in urban society because of environmental factors rather than "genetic deterioration," an epidemiological transition (Omran, 1971) in occlusal health accompanies urbanization.

Western society has completely crossed this transition and now exists in a state of industrially buffered environmental homogeneity. The relatively constant environment both raises genetic variance estimates (since environmental variance is lessened) and renders epidemiological surveys largely meaningless because etiological factors are largely uniform. Nevertheless most occlusal epidemiology and heritability surveys are conducted in this population rather than in developing countries currently traversing the epidemiological transition.

In other words, the reason observational studies in affluent nations haven't been able to get to the bottom of dental/orthodontic problems and chronic disease is that everyone in their study population is doing the same thing! There isn't enough variability in the diets and lifestyles of modern populations to be able to determine what's causing the problem. So we study the genetics of problems that are not genetic in origin, and overestimate genetic contributions because we're studying populations whose diet and lifestyle are homogeneous. It's a wild goose chase.

That's why you have to study modernizing populations that are transitioning from good to poor health, which is exactly what Dr. Weston Price and many others have done. Only then can you see the true, non-genetic, nature of the problem.

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.  You practically can't read a paper on overweight without seeing an obligatory nod to the thrifty gene hypothesis. The only problem is, it doesn't make much sense.

The assumption that hunter-gatherers and non-industrial agriculturalists lived under chronic calorie deprivation isn't well supported. 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. Yet they were not fat.

The Kitavans are a good example. They are a horticultural 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 (leptin, insulin, 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 the thrifty gene hypothesis 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.

Lessons From the Pima Indians

At 38% and climbing in 2006, the Pima indians (Akimel O'odham) of Arizona have the highest rate of diabetes of any population in the world. They also have staggering rates of obesity (~70%) and hypertension.

Things were very different for them before 1539, when the Spanish first made contact. They lived on an agricultural diet of beans, corn and squash, with wild fish, game meat and plants. As with most native people, they were thin and healthy while on their traditional diet.

In 1859, the Pima were restricted to a small fraction of their original land along the Gila river, the Pima Reservation. In 1866, settlers began arriving in the region and diverting the Gila river upstream of the reservation for their own agriculture. In 1869, the river went dry for the first time. 1886 was the last year any water flowed to the Pima Reservation in the Gila river.

The Pima had no way to obtain water, and no way to grow crops. Their once productive subsistence economy ground to a halt. Famine ensued for 40 desperate years. The Pima cut down their extensive mesquite forests to sell for food and water. Eventually, after public outcry, uncle Sam stepped in.

The government provided the Pima with subsidized "food": white flour, sugar, partially hydrogenated lard, and canned goods. They promptly became diabetic and overweight, and have remained that way ever since.

The Pima are poster children for mainstream nutrition researchers in the US for several reasons. First of all, their pre-contact diet was probably fairly low in fat, and researchers love to point out that they now eat more fat (comparable to the average American diet). Another reason is that there's another group of Pima in Mexico who still live on a relatively traditional diet and are much healthier. They are genetically very similar, supporting the idea that it's the lifestyle of the American Pima that's causing their problems. The third reason is that the Mexican Pima exercise more than the Arizona Pima and eat a bit less.

I of course agree with the conclusion that their lifestyle is behind their problems; that's pretty obvious. I think most Pima know it too. If they got their water back, maybe things would be different for them.

However, the focus on macronutrients sometimes obscures the fact that the modern Pima diet is pure crap. It's mostly processed food with a low nutrient density. It also contains the two biggest destroyers of indigenous health: white flour and sugar. There are numerous examples of cultures going from a high-fat diet to a lower-fat "reservation food" diet and suffering the same fate: the Inuit of Alaska, the Maasai and Samburu of Kenya, tribes in the Pacific Northwestern US and Canada, certain Aboriginal groups, and more. What do they all have in common? White flour, sugar and other processed food.

The exercise thing is somewhat questionable as well. True, Mexican Pima exercise 2.5 times more than Arizona Pima, but the Arizona Pima still exercise much more than the average American! Women clock in at 3.1 hours a week, while men come in at a whopping 12.1 hours a week! I am a bike commuter and weight lifter, and even I don't exercise that much. So forgive me if I'm a little skeptical of the idea that they aren't exercising enough to keep the weight off. 

The history of the Pima is a heart-wrenching story that has been repeated hundreds, perhaps thousands of times all over the world. Europeans bring in white flour, sugar and other processed food, it destroys a native populations' health, and then researchers either act like they don't understand why it happened, or give unsatisfying explanations for it.

The Pima are canaries in the coal mine, and we can learn a lot from them. Their health problems resemble those of other poor Americans (and wealthier ones also, to a lesser extent). This is because they are both eating similar types of things. The problem is creeping into society at large, however, as we rely more and more on processed wheat, corn, soy and sugar, and less on wholesome food. Obesity in the US has doubled in the past 30 years, and childhood obesity has tripled. Diabetes is following suit. Life expectancy has begun to diminish in some (poor) parts of the country. Meanwhile, our diet is looking increasingly like Pima reservation food. It's time to learn a lesson from their tragedy.