My recent series on diet and cardiovascular health has produced some interesting findings. Within these findings, I have noticed some intriguing patterns. Following in the tradition of my “Tales of Two Maps” series, here are another set of two maps:
This is the previously featured map of the year 2000 mortality rate from cardiovascular disease in Europe, drawn from here. As we see, there is a distinct northeast to southwest cline. (Although not highlighted here, rates are significantly higher in Russia; if it were colored, it would be very much bright red.)
I wanted to know if there was any simple explanation for this obvious geographic pattern, and then a look back at one of my previous posts gave me a clue:
This is a map of average minimum winter temperatures across Europe. Note how this map correlates to the above map almost perfectly. While the climate of Europe has varied considerably over the ages, we can still get a rough idea of how things were in the past.
But why does this matter? Well, Europeans have been farming for many thousands of years. In the colder climates, growing seasons were shorter. This meant that bulking up on calories was critical during the warm months, to help to survive the long, cold, dark, and very lean winters.
To get an idea of what this has done to modern European populations, see this passage in the previously cited Rob Dunn article:
A Body is Not a Body—Amazingly, there are more ways in which a calorie is not a calorie. Even if two people were to somehow eat the same sweet potato cooked the same way they would not get the same number of calories. Carmody and colleagues studied a single strain of heavily inbred lab mice such that their mice were as similar to each other as possible. Yet the mice still varied in terms of how much they grew or shrank on a given diet, thanks presumably to subtle differences in their behavior or bodies. Humans vary in nearly all traits, whether height, skin color, or our guts. Back when it was the craze to measure such variety European scientists discovered that Russian intestines are about five feet longer than those of, say, Italians. This means that those Russians eating the same amount of food as the Italians likely get more out of it. Just why the Russians had (or have) longer intestines is an open question. Surely other peoples differ in their intestines too; intestines need more study, though I am not going to volunteer to do the dirty work. We also vary in terms of how much of particular enzymes we produce; the descendents of peoples who consumed lots of starchy food tend to produce more amylase, the enzyme that breaks down starch. Then there is the enzyme our bodies use to digest the lactose in milk, lactase. Many (some say most) adults are lactose deficient; they do not produce lactase and so do not break down the lactose in milk. As a result, even if they drink milk they receive far fewer calories from doing so than do individuals who produce lactase. Each of us gets a different number of calories out of identical foods because of who we are and who our ancestors were.
Russians (on one end of the spectrum) have evolved to more thoroughly extract the calories from their food than Italians (who are on the other end of the spectrum). I wouldn’t be surprised if other Europeans fall in between in intestinal length, in accordance with the above maps.
In addition to varying on the amount of calories extracted from food, people vary in what their bodies do with those calories:
Ultimately, the relationship between physical activity and fatness comes down to the question of cause and effect. Is Lance Armstrong excessively lean because he burns off a few thousand calories a day cycling [Jayman: or injected a few thousand units of performance enhancing substances, but anyways], or is he driven to expend that energy because his body is constitutionally set against storing calories as fat? If his fat tissue is resistant to accumulating calories, his body has little choice but to burn them as quickly as possible: what Rony and his contemporaries called the “activity impulse”—a physiological drive, not a conscious one. His body is telling him to get on his bike and ride, not his mind. Those of us who run to fat would have the opposite problem. Our fat tissue wants to store calories, leaving our muscles with a relative dearth of energy to burn. It’s not willpower we lack, but fuel.
For the last 60 years, researchers studying obesity and weight regulation have insisted on treating the human body as a thermodynamic black box: Calories go in one side, they come out the other, and the difference (calories in minus calories out) ends up as either more or less fat. The fat tissue, in this thermodynamic model, has nothing to say in the matter. Thus the official recommendations to eat less and exercise more and assuredly you’ll get thinner. (Or at least not fatter.) And in the strict sense this is true—you can starve a human, or a rat, and he will indeed lose weight—but that misses the point. Humans, rats, and all living organisms are ruled by biology, not thermodynamics. When we deprive ourselves of food, we get hungry. When we push ourselves physically, we get tired.
From this biological or homeostatic perspective, lean people are not those who have the willpower to exercise more and eat less. They are people whose bodies are programmed to send the calories they consume to the muscles to be burned rather than to the fat tissue to be stored—the Lance Armstrongs of the world. The rest of us tend to go the other way, shunting off calories to fat tissue, where they accumulate to excess. This shunting of calories toward fat cells to be stored or toward the muscles to be burned is a phenomenon known as fuel partitioning.
In short, evolution may have conditioned various people to respond differently to food based on their ancestors’ level of food availability (and effort required to get it). In the balmy Mediterranean parts of Europe, food was probably more available all year round, reducing the need for the inhabitants to develop super-efficient digestive systems. Today, when exposed to the rich supply of foodstuffs of all sorts today, their bodies are better able to tolerate it.
By contrast, those in the colder, snowier Northern and Eastern parts of Europe may have evolved a stronger desire to consume food whenever it’s available, particularly carbohydrates. (However, northern Europeans don’t seem to be more prone to storing fat, as this map indicates, with the exception of the Brits–as with their American offshoots.) Northern and Eastern Europeans may faced a trade-off with their efficiency at absorbing and processing calories coming at the cost of long-term cardiovascular health.
Interestingly, the map of winter temperatures, particularly the 0° C isotherm seems to correlate well to the points in Spain and Italy where average IQ starts to drop, as I’ve noted previously.
The drop in hearth health in Britain may have something to do with the lower levels of sunlight it receives, which may stunt farming there. As well, the drop in heart health (and IQ) that occurs in the Celtic fringes may be do to the history of pastoralism there, thanks to the rockier and poorer quality soil (very evident in Scotland).