Survival of the Fittest

We live in a weight obsessed society. More specifically, obsession with being thin. There are a lot of people who harm themselves by trying to obtain the thinness they feel society expects of them. From a biological standpoint, thin is not in.

I did a blog post a while ago which I entitled, “Mutant Bulldogs”.  In that post I talked about natural selection. It might be helpful to go reread that because I mentioned several examples of natural and artificial selection.

Let me just explain a little bit about what natural selection is. Natural selection is a term coined by Charles Darwin. In a nutshell, natural selection says that individuals with certain genetic characteristics have the advantage over those without those genetic characteristics. And therefore are more easily able to survive and reproduce.

I will give you an example. Prior to the Industrial Revolution in the United Kingdom there was a certain species of moth with approximately half of the population being white in color and half being black. After the Industrial Revolution there was a lot of soot that covered the trees in which the moths lived. It became much easier for predators to see the white colored moths. Therefore, being black in color was naturally selected for in these specific moths. The black moths survived to reproduce much more easily than did the white moths. Therefore the population was skewed to favor black moths. This is natural selection.

Another term for natural selection is survival of the fittest. Biologically speaking, fitness refers to the ability to survive to adulthood and produce offspring. More specifically, fitness is measured by how many offspring you leave behind.

When most people think of fitness they think of big muscles, athletic ability, low body fat percentage, etc. All of those things do play a role in physical fitness and perhaps to a small degree in natural selection. When I speak of fitness, I am speaking in biological terms, not physical fitness as you know it.

In the animal kingdom it is quite evident that, for example, in zebras, lions, antelopes, cheetahs, etc. the ability to run fast would be advantageous. Therefore, the ability to run fast is a trait which would be naturally selected for in the above example.

Natural selection is not as important in human populations because, as a species, we tend to care for those who are “not as fit”.  For example, people with genetic disorders that cause physical or mental disabilities. Those individuals thus afflicted, are cared for by others. Whereas, in the animal kingdom they wouldn’t survive long.

In times of stress however, you would see natural selection, or survival of the fittest, taking place in human populations. For example, during a famine those individuals with a fat reserve, whose bodies can slow metabolism will have an advantage over those with little or no fat reserve with a high metabolism.

That’s what I want to talk about today. I want to focus on natural selection and specifically the body’s ability to store fat.

One of the traits that would make us less fit, is the inability to store fat. Therefore, those individuals who are extremely thin, who can’t seem to put any weight on regardless of how much food they eat, are less fit, biologically speaking, than those who carry around a few extra pounds. Even though society tells us that thinner is better. Biology tells us otherwise. We need a little “meat on our bones”. Those extremely thin supermodels that you see on magazine covers are less fit than the average person. The other extreme is true as well, those who are morbidly obese, are also less fit.

But I want to focus on our quest for thinness. Biologically, it doesn’t make sense. It might be hard to understand this concept in the world in which we live today, where food is abundant. But, think about times of famine. Who is more likely to survive, a thin person with relatively little fat storage, and a high metabolism, or someone who is carrying around 20 or 30 pounds of excess fat, and has a slower metabolism?

Actually, the ability to slow your metabolism in times of famine is a naturally selected for trait. Have you ever wondered why crash diets don’t work very well? It’s because when you severely restrict your caloric intake, your body slows your metabolism because it thinks there’s a famine. Therefore, making it much more difficult to lose weight. The calories you do eat are stretched farther, and your fat stores are conserved as much as possible.

The most effective and safest way to lose weight is slowly. By slightly modifying your diet; decreasing caloric intake, and increasing your exercise regimen; increasing caloric output. It’s quite a simple formula really. Burn more calories than you consume equals weight loss. Consume more calories than you burn equals weight gain.

Exercise, even a small amount, tends to increase metabolism. That is, if there is enough energy available through daily food intake. This is why you should not restrict caloric intake very much. Because, as I said before, if you restrict daily caloric intake too much, your body actually slows metabolism. You can still lose weight this way, because as mammals we are endothermic (warm blooded) and require a lot of energy to sustain life. But, as soon as the “famine” is over, you’ll much more easily gain weight back. Usually as much or more than you lost. Because your metabolism is much slower than normal and your body is preparing for the next famine.

Since I’m on the subject of diet and nutrition. Let me mention that moderation in all things is always the best policy. A healthy body requires a variety of foods. This is how we acquire the essential amino acids, vitamins, minerals, micronutrients, etc. needed.

As I recall, a healthy diet consists of around 60% carbohydrates of which the majority should be complex carbohydrates obtained through grains in the form of bread, rice, cereals, and pastas. 10% of our diet should consist of proteins, these are usually obtained from meats but can also be obtained through dairy products, eggs, and certain legumes like peanuts and beans. And lastly, 30% or less of our daily caloric intake should be obtained from fats. Let us remember that fats contain 9 kcal per gram. Whereas proteins and carbohydrates contain 4 kcal per gram. So a gram of butter contains more than twice as many calories as the same amount of sugar.

Fats seem to get a bad rap. So, let me take a moment to defend them. Not only do fats produce satiety when eaten, they also help you feel satiated longer. Have you ever noticed people who are on a no fat diet always feel hungry? It’s because they are not eating the fats necessary to be satiated.

Let me give you an example. A person on a no fat diet eats a plain baked potato. They don’t feel full so they eat another one. They rationalize that since they didn’t put butter and sour cream on their potato, they can eat twice as much. Whereas the person who eats the same baked potato with butter and sour cream on it feels full after eating just one.

Now let’s compare caloric intake. A plain baked potato has 280 calories. The same baked potato with butter and sour cream has 455 calories. So, the person on the no fat diet who ate two plain baked potatoes consumed 540 calories. And will still get hungry a lot faster because he ate no fat. While the person who ate one baked potato with butter and sour cream consumed 455 calories and will feel fuller longer because of the fat on his potato.

Let’s see, the person on the low-fat diet consumed almost 100 more calories than his wiser counterpart. But he still feels better about himself because he didn’t eat any fat. In the words of Capt. Woodrow F. Call, “That don’t make no sense at all”.

I guess my point in writing this blog post is to say that moderation in all things is the best policy. Don’t deprive yourself of a variety of foods you enjoy. Go ahead and put butter and sour cream on your potato, eat the chocolate cake, enjoy the works on your pizza, enjoy all the goodies during the holidays. And if you put on a few pounds, just be happy that you are more fit, biologically speaking, than the skinny supermodels on the magazines.

That’s my two cents.