I recently made some critical remarks about an upcoming book called Paleofantasy: What Evolution Really Tells Us about Sex, Diet, and How We Live. While we’ll have to wait on the release of the book to pass judgment on the actual science, the marketing for the book is irksome because it claims to “debunk” the paleo diet while displaying complete ignorance of what claims are actually made by the mainstream paleo community. [Editor's note: The book is now released, see my review here.]
My comments stirred up quite a fuss, and since I am not without an appreciation for irony I’ve decided to write about several views held by paleos that I would call “Paleo Fantasies.”
1. Low carb means no carb
Put that strawberry down! It will spike your insulin right into diabetes and the fructose will rot your veins from the inside out.
Somewhere along the line the idea of “low carb” turned into the idea of “no carb.”
This then prompted a backlash, and there are now some folks running around who launch an attack every time they hear those dastardly low carbers spouting their living la vida low carb lies.
“Low carb” itself is a problematically poorly defined term. Low compared to what?
Compared to the standard American diet (SAD), paleo is low carb. It’s also most likely lower in fat since a lot of the offending foods (pizza, cake, Big Macs, etc.) also contain lots of fat.
Perhaps what we need is not a “low carb” diet or a “high carb” diet, but an “appropriate” carb diet. The fact is that you need some carbs, especially if you are highly active and exercise regularly.
I can’t recall how many times I’ve heard, “I just had no energy after going paleo, so I had to start eating more carbs.”
So if you’ve been no-carbing it, throw a sweet potato or two in the mix, or perhaps get some unsweetened dried fruit from my favorite source (www.nuts.com). It won’t kill you and will help restore your depleted energy.
2. Insulin is the enemy
Pretty much everyone knows that diabetes has something to do with blood sugar and insulin dysfunction.
If you’ve read a little more on the topic you probably have a model in your head something like chronically high carbs leads to chronically high blood sugar, which leads to chronically elevated insulin levels, which leads to insulin insensitivity. Then wham! You’ve got diabetes.
The specter of the carb-diabetes connection is another reason that low carb turns into no carb. Fear of insulin dysfunction turns into fear of insulin in general.
But we should not fear insulin. Like cholesterol, it too has a part to play in the healthy running of our everyday lives. It might even surprise you to know that meat is highly insulinogenic. Like most things it’s probably just chronic excess that is the real problem.
For a more complete and accurate discussion of insulin than I am capable of take a look at Weightology’s four part series on Insulin…an Undeserved Bad Reputation.
3. Being fat adapted means eat unlimited fat
The high fat craze most likely began with Mark Sisson’s announcement that his goal was to create a metabolic paradigm shift from man as “sugar-burner” to man as being “fat-adapted.”
This move appears to have been a backlash against mainstream exercise nutrition practices like carboloading and mainstream diet practices of avoiding fat in foods at all costs. It was a cry out against a mentality that keeping the body fueled means putting in the right amount of sugar–and the more the better.
However, the problem is that some people interpreted this as unrestricted license to eat fat. It also further fueled the fire of low carb=no carb (despite his admonition that it didn’t mean he was anti-carb).
So instead of approaching a reasonable medium, the pendulum swung the other way and fat become the miracle food that you couldn’t eat enough of in some circles.
I can’t speak to other’s experience of fat, but when I eat too much fat I get queasy and sick to my stomach. A trip to the bathroom shortly follows (experiment: try drinking an entire can of coconut milk at once and see how long you can hold it in… or better yet, don’t and just take my word for it).
Art De Vany, another pillar of the paleo community, has spoken out against high fat because fat is inflammatory and damages insulin receptors–neither of which are desirable.
Again, I think the take-away message here is that fat is not evil, but we should avoid chronic excess. Instead of jumping to either extreme of “no fat” or “max fat,” we probably need to seek out the middle ground of “appropriate fat.”
My entirely unscientific method of gauging fat consumption is that if I start to feel queasy, I’ve eaten too much. If I start to get acne or have skin problems, then I need to eat more fat (yes, you read that right, more fat for skin problems–the opposite of what everyone thinks. While I have no scientific data on this I suspect it has something to do with fatty acids repairing the natural oil barriers of the skin. Vegans, especially raw vegans, often complain of dry skin and other skin-related issues which I suspect have to do with fat deficiency in their diet).
4. Calories in vs. calories out is broken
This is somewhat of a half-truth. People have noted that despite the supposed laws of thermodynamics, weight gain and weight loss don’t seem to obey the principle of calories in vs. calories out.
The problem isn’t so much that calories in vs. calories out (CICO) is broken as that what most people think it means is broken. In most people’s mind CICO is typically rendered as:
(Calories eaten) – (Calories burned through exercise) = (Change in weight)
This equation misleads us because calories are also burnt or lost through other ways like simple heat production in the body, other metabolic processes, or getting pooped out without actually being digested. Different foods can also have effects like promoting or reducing water retention in your body, easily creating pounds of difference in your weight (see here for a more complete discussion of factors effecting CICO and weight change).
The popular mis-perception of CICO as well as its general impracticality as a day-to-day tool for how much to eat and exercise leads me to think it is time to cast it aside. Most of us simply aren’t going to calculate our net expenditures on a daily basis, or are going to use “mental math” with margins of error so large as to make the attempt meaningless.
From the diet side I think we are better served by simply keeping our focus on eating nutrient-dense whole foods like lean meats, fruits, and veggies; and avoiding the bad stuff like grains and processed foods.
If you really want a metaphor to use, it’s probably more helpful to think of the body as a “chemistry set” than as a “calorie burning engine.” Focus more on how your body reacts to the quality of your food than on the energy content of your food.
5. Evolution has stopped
This actually kind of seems plausible. Depending on who you talk to humans have had essentially the same genetic makeup for anywhere from 250,000 to 2 million years. And everywhere we look around us humans have essentially been humans for thousands of years.
Of course it simply isn’t true. The most obvious evidence that evolution is still happening has been staring you in the face all your life–different ethnicities have different skin color, hair color, etc. These differences are genetic. You don’t grow up with brown skin just by being born in India or white skin just by being born in Europe.
The gene mutation associated with the typical Asian appearance is only thought to be about 35,000 years old. So their DNA makes the 10,000 year paleo cut off at least, but only just…
As long as we reproduce by DNA exchange, there will be DNA copying errors that produce mutations. Some of those mutations will be favorable either because they help us to survive and produce more children than the next guy or because they make us sexier than all the rest and have more mating opportunities. As those genes increase in the gene pool, evolution marches on with natural selection.
6. There hasn’t been enough evolutionary time to adapt to neolithic foods
Whoa buddy! That food is totally a post-farming invention, put it down.
This is another sort of half truth. It leads to dietary dichotomies like new world foods vs. old world foods and maxims like “only eat something with a biblical Hebrew name.” It also leads to arguments against certain foods solely because they are nightshades (tomatoes, potatoes, green peppers, eggplants etc.), with scant explanation of why that even matters.
Of course it should be patently obvious that while there may be some correlation to ancestral adaptation, whether a plant grows in the new world or the old world or whether or not it has a biblical hebrew name is not a scientific method for determining nutritional value.
Typically anytime you hear someone talk about a paleo “gray zone,” you are usually talking about one of these neolithic foods that just might be okay despite lacking its 10,000 year pedigree.
Now, the problem with the “not enough evolutionary time” argument is that it is wrong due to a concept called “punctuated equilibrium.”
The idea is that a severe enough environmental stressor can cause a rapid change in the gene pool, sometimes in as little as a single generation.
For example if your food supply gets poisoned with arsenic, most people would die. But some, even if only a very tiny percentage, would survive–only those capable of eating arsenic. This is exactly what happened to some populations of earthworms.
Milk consumption and lactase persistence are evidence of punctuated equilibrium at work in humans. A BBC documentary a few years ago cited evidence for strong selection pressure for milk consumption. Of course the conversion is not “complete”–some of us deal with milk better or worse than others.
And some things like nightshades may simply never have been a problem for most folks to begin with.
Now, all that said it doesn’t mean that we need to throw the evolutionary framework out the window. All it means is there is nothing magical about the exact 10,000 year barrier and that you may have to do a little experimentation to see what works for you instead of sticking religiously to a set of dietary commandments.
7. We are perfectly adapted to the diet of our paleolithic ancestors
This is one area where Marlene Zuk, author of Paleofantasy, is likely right on the money.
In her New York Times article The Evolutionary Search for Our Perfect Past she asks just what exactly is this paleo diet we are supposedly perfectly adapted to.
The Inuit who were still living a paleolithic lifestyle in recorded memory ate almost entirely animal based diets, relying heavily on native aquatic life. The !Kung people in the Kalahari relied heavily on the roots of desert plants and the occasional giraffe or antelope catch. And the plants and animals eaten by our paleolithic ancestors in Africa, Asia, Europe, and even North America all would have been very different from one another.
A “paleo diet,” if it really exists, is many and varied different diets that share loosely common themes. Instead of asking if a specific food is “paleo” or not, we should ask if it is nutritious and if our bodies respond well to eating it (many of us, including me, unconsciously mean this when we ask if something is “paleo,” but it’s important to remember what we really mean).
Undoubtedly there is a strong genetic component to this and on average what is healthy for others will be the same as what is healthy for you, but the sheer fact that nearly all paleo figureheads advocate individual testing to see how your body reacts to different foods should explode the notion of a 100% perfect one-size-fits-all adaptation to a specific eating formula.
It’s better to think of paleo as a framework that gives hints at the probability of what foods will be healthy for us.
But more importantly, the idea of perfect adaption speaks to a fundamental misunderstanding of evolution itself. Evolution doesn’t make a species perfectly adapted to its environment, it only ensures that those better adapted to it than the next guy (or perhaps more to the point, “less badly adapted to it” than the next guy) have a better chance of surviving and having children. This can leave us in a sort of “half-adapted” state (remember our earlier conversation about milk?).
Like the man running from the bear said to his friend, “I don’t have to be faster than the bear, just faster than you.”
A funny twist on the notion of adaptation is that in the documentary The Perfect Human Diet someone is shown giving a presentation on the human digestive tract saying essentially, “Look, we don’t have four stomachs and a long digestive tract, we have a short digestive tract like a carnivore. Clearly we were meant to eat meat [slide in the background shows pictures of a cow, lion, and human digestive tract].”
Coming the other direction, vegetarians and vegans use almost the exact same argument! They say, “Look, our digestive tract is way longer than carnivores’, clearly we were meant to be herbivores.”
The truth is somewhere in the middle. We have a longer digestive tract than a carnivore but a smaller one than an herbivore, which reveals our omnivorous nature.
I use the metaphor that our digestive system is like a swiss army knife.
It’s built to do many different things and can be adapted to new uses. But it doesn’t do any of those things particularly well (compared to a specialized one-purpose tool), and none of them exclusively. It’s de-optimized on both the veggie end and the meat eating end to give us a broad range of dietary options that we are all imperfectly adapted to.