Thursday, April 29, 2010

Learning From the Kitavans

Sometimes we paleo folks cringe a bit in our seats when the Kitavans of Papua New Guinea are brought under discussion. The existence of the Kitavans seems to somehow challenge some of our assumptions about what aspects of a paleo diet really drive its health benefits, or even what a paleo diet is.

The Kitavans is a hunter-gatherer/semi-agriculturalist population whose members eat a diet composed of a whopping 70% of calories from carbs, only 20% from fat, and the remaining 10% from protein.

Yet with this high carb diet, the Kitavans are exhibiting the absence of obesity and disease that we associate with our standard paleo template which typically prescribes a diet much lower in carbs, much higher in fat, and higher in protein than the Kitavans' standard fare.

Further, as we tend to be fans of Gary Taubes' meticulously worked out thesis that carbohydrates drive insulin, and that insulin drives fat storage and obesity, we might be tempted to pull an Ancel Keys on the Kitavans and relegate them to some sideshow of "irrelevant" outliers.

So what's really going on with the Kitavans and how do they fit within our paleo world view?

The following discussion doesn't try to cover all the factors that may be at play, but I think that it will illustrate how the integration of observations of the Kitavans into our big picture actually deepens and strengthens our understanding of the virtues of a paleo approach to diet.

In order to proceed we need to recognize that Taubes' carbohydrate hypothesis must be interpreted within the context of additional hormonal- and environmental factors besides insulin and carbohydrates.

One of the most important factors in this regard seems to be hormone leptin, and the ways by which its function may be interfered with.

Leptin is a hormone secreted by the fat tissue which speeds up metabolism and acts as an appetite suppressant. Leptin also helps to ensure that fat is neatly stored in our fat cells, and that it is not instead packed between- or inside our organs, which is a very disruptive situation associated with Western disease.

One could say that leptin is the fat tissue's way of ensuring a peaceful relationship with other tissues in the body so that an appropriate amount of spare calories can be stowed away as fat, but no so much that the fat deposits grow dysfunctionally large.

Now, quite unfortunately, there is such a thing as leptin resistance, which makes our brains deaf to the fat tissue's leptin signal. This deafness to leptin in turn makes us hungrier than we should be, and thus allows fat deposits to expand more readily, and also into places, such as the liver, where we absolutely don't want any fat. (With a nod to Tabues, I must say that eating insulin-spiking carbs certainly doesn't help in this situation, but there is such a thing as over-eating fat and protein too, especially in the context of a slowed down metabolic rate.)

Leptin resistance can be caused through different avenues (one of them over-consumption of carbs, particularly fructose), but more to the point in our discussion of the Kitavans is that certain proteins (lectins) in grains may be a powerful causal factor in leptin resistance through blocking leptin receptors in the brain.

This potential for grains-induced leptin resistance helps to explain why Westerners eating a 60% carb diet based on a large amount of grains become leptin resistant and wind up with obesity and associated metabolic problems, whereas the Kitavans who might consume the same proportion of carbs in their diet, though from non-grain sources such as root vegetables, instead maintain leptin sensitivity, a lean body composition and the absence of disease .

The above line of reasoning is put forth and supported by two very compelling papers by Staffan Lindeberg, et al, and Tommy J├Ânsson, et al. (The latter is a particularly excellent example of a carefully constructed hypothesis that integrates observations from epidemiology and evolutionary biochemistry - highly recommended for the science geek.)


Another set of hormonal- and environmental factors that potentially have bearing on why the Kitavans are so healthy may be the hormone adiponectin and the nutrional factors that impact its production.

Adiponectin is a hormone that (as is the case with leptin) is secreted by the fat tissue, which quenches inflammation and increases insulin sensitivity. Adiponectin thus acts as the body's own antidote against the metabolic syndrome's hall mark symptoms which are precisely insulin resistance and inflammation. Similar to leptin, adiponectin is likely one of natures' way to make sure that we can expand our fat stores without adverse systemic side effects.

In people with metabolic disease, the levels of adiponectin have been found to typically drop off rapidly as the affected individuals become more obese, though this doesn't happen uniformly from individual to individual. The correlation between a given person's level of obesity and corresponding drop in adiponectin (and associated rise in metabolic problems) seems to be determined by genes and gender (women tend to produce more), but levels of adiponectin have also been positively correlated with the presence of the minerals magnesium and calcium in the diet.

Interestingly, a dietary factor that is recognized as interfering with the absorption of magnesium, calcium, and other minerals is the lectins and phytic acid present in grains and legumes.

In other words, foods that mainstream Westerners tend to eat as dietary staples (particularly grains) block the minerals that promote adiponectin, while the Kitavans do not eat these mineral blocking foods!

I haven't seen any data on this, but I would not be surprised if it is the case that to the extent that the Kitavans actually become a little chubby (such as the individual to the right in the picture above), they probably also have higher levels of adiponectin compared to Westernes with similar body composition, and that one potential explanation for this is that the Kitavans are less prone to mal-absorption of crucial minerals. (Of course the absence of mineral deficiency also has other wide ranging positive effects.)

To wrap up this discussion, we can see that qualitative aspects of a diet (such as, in this case, the presence or absence of grains) may quite dramatically condition how our bodies deal with a particular ratio of macro nutrients, or availability of calories for that matter. (A person with his leptin receptors blocked by grain lectins tends to be a hungrier person! )

This in turn hints at a really cool epistemological aspect of the paleo dietary approach: Paleo doesn't focus on individual nutrients in a narrowly mechanistic manner. Instead it provides us with a integrative framework that isn't at all threatened by new observations or the presence of unusual cases. I don't know of any other dietary- or lifestyle approach that accomplishes this.

PS. Eating 60% of calories from carbs may not be for everyone. Those who struggle with obesity and/or insulin resistance should try low carb paleo.

Wednesday, April 7, 2010

Carb Cravings - Type 1, 2, and 3.

This is a discussion about some distinctions that I think are helpful when discussing carb cravings on paleo, and how to address them.

First of all, I'd like to mention that a paleo diet doesn't necessarily need to be ultra low in carbohydrates, but it is definitely low in refined- and "neolithic"- carbs. Candy, cake, grains, and legumes must go!

Secondly, from a health effect point of view, the difference between a moderate carb paleo diet and lower carb paleo diet is that the former prevents and cures the metabolic syndrome and numerous related diseases, while the lower carb variant does all of this plus helps you burn your subcutaneous body fat to a larger degree.

Now with this out of the way let's look at three common categories of carb cravings.

Type 1 - Energy dependence.

This type is about running out of fuel for the brain because one's body simply hasn't yet adapted to burning fat effectively. This is likely unavoidable for most people transitioning from the USDA-diet to proper eating during at least the first six weeks.

Symptoms: Light-headedness, irritation, fatigue, blurry vision, headache. In other words, the classic symptoms of low blood sugar: "hypoglycemia".

Panic cure (e.g., behind the wheel): dextrose tablet.

General short term cure: A few pieces of dark chocolate, a small serving of fruit. Nuts may also work for some. The principle is to get a little pick-me-up to a comfortable baseline without causing a dramatic sugar-shock. (We don't want shocks, because those cause the body to think that more of the same will be coming and thus it may resist normalizing its hormonal regulation.)

Long term cure: Continue to eat paleo. Eventually the need for carbs will be zero to moderate from an energy standpoint (special cases, such as endurance athletes, aside). Include fruits and veggies for the micro-nutrients in them, not because your brain stops without sugar. Though also allow for the observation that some people function better on a slightly higher carb diet. (Experiment!)

Type 2 - Chemical addiction.

This is about an addiction to carbs' secondary effects on brain chemistry, particularly their triggering of a temporary surge in the feel-good neurotransmitter serotonin, as well as cravings for addictive compounds (for example opioid peptides) that are found inside some carby foods (for example wheat).

Most USDA-eating individuals probably suffer from a bit of both type 1 and type 2 cravings, but, fortunately, a paleo diet (including supplementation with omega 3 oil, and vitamin D) also inherently addresses both types.

As stated above, type 1 is primarily an issue of one's body's fuel preference, and goes away over time as one's metabolism adapts to fat utilization.

Type 2, on the other hand, is primarily a neurotransmitter issue, and a bit more tricky (chemical addictions tend to be), but is typically addressed by the paleo diet's serotonin promoting properties (specifically, for example, the presence of serotonin precursors in meat, and omega 3's and vitamin D's beneficial impact on serotonin production and utilization).

One should, in fact, expect a better general mood after some time on the serotonin boosting paleo diet versus a USDA type diet which only produces brief surges in serotonin followed by slumps. (If this doesn't happen for you, check out Nora Gedgaudas' blog post for some troubleshooting hints.)

As a short term fix (slightly mimicking the boom-bust effect of carbs on serotonin), I think that coffee might do the job for some.

Type 3 - Psychological addiction.

When intermingled with type 1 and type 2, psychological addiction seems to be a very problematic aspect for a lot of people. The thought of Mom's savory fudge, newly baked scones at Hotel Claridges in London, Pedro's heavenly burritos, etc can trigger formidable cravings.

Unfortunately, I don't have that much to say about how to deal with this aspect, which seems to be more problematic than anything else for some, but wasn't an issue in my own case.

So far, I think that Rick Kiessig's recommendation in regard to retraining oneself represents the best shot at this issue:

"… to find something that I liked as well as carbs, that was an acceptable Paleo food, but that had also been considered relatively taboo previously. In my case, that ended up being cream, in several different forms (plain, mixed with a little milk, mixed with baking cocoa, whipped, etc). If I had a carb craving, I trained myself to have a cup of cream instead."

We will hopefully have posts in the future that deal further with the psychological issues related to switching to a new way of eating.

Thursday, April 1, 2010

Healthy BMI from a Paleo Point of View

A recent Canadian study has found certain BMI ranges to be more or less correlated with mortality, and quite counter-intuitively the study found that being overweight to mildly obese is the least risky - even somewhat less risky than having a normal BMI.

Here is a summary of the findings: ("Normal weighted" individuals at a BMI of 18.5 to 25 were assigned a risk score of 1.00.)
  • Underweight, BMI less than 18.5; relative risk (RR) = 1.73, a significantly increased risk of death
  • Overweight, BMI 25-30; RR = 0.83, a significantly decreased risk of death
  • Obesity class I, BMI 30-35; RR = 0.95, neutral
  • Obesity class II+ , BMI over 35; RR = 1.36, an increased risk of death
Since BMI doesn't distinguish between fat- and muscle mass, theoretically some athletic people in this study may have been mischaracterized as obese, but I think that it is safe to assume that the majority in the higher BMI groups were carrying more mass as fat than subjects with lower BMIs.

So, what's going on here? Should we interpret this study as a license to be flabby?

Not quite, I think.

I believe that such a blunt measure as BMI (or similar ones that ignore body composition) may only be valid as a predictor in a population with epidemic overt-, or borderline metabolic syndrome.

[Note: "The metabolic syndrome" is the name of a cluster of pathologies such as type 2 diabetes and CVD resulting from insulin resistance in the liver caused by excess fructose, gut irritants (e.g., gluten), and omega 6 fats in the diet. See Peter's blog for all about this.]

My primary reasons for the above assertion is that when looking at such populations (virtually all in the West) we can be certain that…

1)…many of those individuals who are classified as "underweight" or normal weighted are either sick and malnourished or, most importantly, "skinny-fat". Being skinny fat (as I used to be, and as are most of those who "can eat anything without gaining weight") may be especially dangerous because this condition indicates a lack of protective fat cells. Yes, it is becoming clearer and clearer that people who grow obese are protected by their own fat cells against the effects of bad diets compared to those who don't.

[Digression: The fate of the skinny-fat after, say, the age of 35 is a gradual descent into accelerating metabolic derangement which is at first smartly hidden from sight, but then later may manifest as one or more of the following: high blood pressure, migraines, cancer, hormonal disturbances, mood disorders, pre-mature aging, puffiness in the face, a hint of a double chin, and systemic inflammation. The irony is that these folks believe that they are successfully living the "healthy whole-grain" lifestyle. I know because I was one of them.]

2)…the "overweight" are either muscular (rare) or in the sweet spot of temporarily being protected from the metabolic syndrome by their fat cells (this is the typical chunky guy on the street); and that those who are fatter than that, "obesity class II+", are beyond protection (which only goes so far) and die early because of it.

However, and this is the kicker, once one has controlled for the metabolic syndrome (or put everyone on a paleo diet for 12 months), a different health equation goes into effect, which kicks these Western BMI studies in their soft underbellies.

Hunter-gatherers' BMIs are typically in the lower range of what's considered normal in Western contexts, and their body fat is roughly 10% for males, and 20% for women.

However, given hunter-gatherers' gold standard health (as documented for example here recently, and in numerous other places) wich by far surpasses what's considered normal in Western populations, it would be absolutely wrong for these hunter-gatherers to conclude that they should pack on extra weight (aside from muscle), say by eating some pasta or bread, to reach the BMI range with the lowest observed mortality risk by the standard of studies on Western corn-fed, metabolically deranged, people.

Conversely, what non paleo people in general should do is to rid themselves of the metabolic syndrome by adopting modern paleo principles including some high intensity exercise, and let their BMIs go wherever they need to go in that process. (Fat loss towards aesthetic satisfaction is usually part of the same package, but may require more tweaking.)

To sum up: Having a BMI in the "healthy" range according to Western epidemiological studies, yet with the metabolic syndrome still brewing, is not good enough if long term health is one's goal.

[Editor's Note: Whereas BMI is flaky at best, A1C or "glycated hemoglobin" may be a good marker for one's general health status.]

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