No fat gain while eating well during the Holiday Season: Palatability isolines, the 14-percent advantage, and nature’s special spice

Like most animals, our Paleolithic ancestors had to regularly undergo short periods of low calorie intake. If they were successful at procuring food, those ancestors alternated between periods of mild famine and feast. As a result, nature allowed them to survive and leave offspring. The periods of feast likely involved higher-than-average consumption of animal foods, with the opposite probably being true in periods of mild famine.

Almost anyone who adopted a low carbohydrate diet for a while will tell you that they find foods previously perceived as bland, such as carrots or walnuts, to taste very sweet – meaning, to taste very good. This is a special case of a more general phenomenon. If a nutrient is important for your body, and your body is deficient in it, those foods that contain the nutrient will taste very good.

This rule of thumb applies primarily to foods that contributed to selection pressures in our evolutionary past. Mostly these were foods available in our Paleolithic evolutionary past, although some populations may have developed divergent partial adaptations to more modern foods due to recent yet acute selection pressure. Because of the complexity of the dietary nutrient absorption process, involving many genes, I suspect that the vast majority of adaptations to modern foods are partial adaptations.

Modern engineered foods are designed to bypass reward mechanisms that match nutrient content with deficiency levels. That is not the case with more natural foods, which tend to taste good only to the extent that the nutrients that they carry are needed by our bodies.

Consequently palatability is not fixed for a particular natural food; it does not depend only on the nutrient content of the food. It also depends on the body’s deficiency with respect to the nutrient that the food contains. Below is what you would get if you were to plot a surface that best fit a set of data points relating palatability of a specific food item, nutrient content of that food, and the level of nutrient deficiency, for a group of people. I generated the data through a simple simulation, with added error to make the simulation more realistic.

Based on this best-fitting surface you could then generate a contour graph, shown below. The curves are “contour lines”, a.k.a. isolines. Each isoline refers to palatability values that are constant for a set of nutrient content and nutrient deficiency combinations. Next to the isolines are the corresponding palatability values, which vary from about 10 to 100. As you can see, palatability generally goes up as one moves toward to right-top corner of the graph, which is the area where nutrient content and nutrient deficiency are both high.

What happens when the body is in short-term nutrient deficiency with respect to a nutrient? One thing that happens is an increase in enzymatic activity, often referred to by the more technical term “phosphorylation”. Enzymes are typically proteins that cause an acute and targeted increase in specific metabolic processes. Many diseases are associated with dysfunctional enzyme activity. Short-term nutrient deficiency causes enzymatic activity associated with absorption and retention of the nutrient to go up significantly. In other words, your body holds on to its reserves of the nutrient, and becomes much more responsive to dietary intake of the nutrient.

The result is predictable, but many people seem to be unaware of it; most are actually surprised by it. If the nutrient in question is a macro-nutrient, it will be allocated in such a way that less of it will go into our calorie stores – namely adipocytes (body fat). This applies even to dietary fat itself, as fat is needed throughout the body for functions other than energy storage. I have heard from many people who, by alternating between short-term fasting and feasting, lost body fat while maintaining the same calorie intake as in a previous period when they were steadily gaining body fat without any fasting. Invariably they were very surprised by what happened.

In a diet of mostly natural foods, with minimal intake of industrialized foods, short-term calorie deficiency is usually associated with short-term deficiency of various nutrients. Short-term calorie deficiency, when followed by significant calorie surplus (i.e., eating little and then a lot), is associated with a phenomenon I blogged about before here – the “14-percent advantage” of eating little and then a lot (, ). Underfeeding and then overfeeding leads to a reduction in the caloric value of the meals during overfeeding; a reduction of about 14 percent of the overfed amount.

So, how can you go through the Holiday Season giving others the impression that you eat as much as you want, and do not gain any body fat (maybe even lose some)? Eat very little, or fast, in those days where there will be a feast (Thanksgiving dinner); and then eat to satisfaction during the feast, staying away from industrialized foods as much as possible. Everything will taste extremely delicious, as nature’s “special spice” is hunger. And you may even lose body fat in the process!

But there is a problem. Our bodies are not designed to associate eating very little, or not at all, with pleasure. Yet another thing that we can blame squarely on evolution! Success takes practice and determination, aided by the expectation of delayed gratification.

The bipolar disorder pendulum: Depression as a compensatory adaptation

As far as explaining natural phenomena, Darwin was one of the best theoretical researchers of all time. Yet, there were a few phenomena that puzzled him for many years. One was the evolution of survival-impairing traits such as the peacock’s train, the large and brightly colored tail appendage observed in males.

Tha male peacock’s train is detrimental to the animal’s survival, and yet it is clearly an evolved trait ().

This type of trait is known as a “costly” trait – a trait that enhances biological fitness (or reproductive success, not to be confused with “gym fitness”), and yet is detrimental to the survival of the individuals who possess it (). Many costly traits have evolved in animals because of sexual selection. That is, they have evolved because they are sexy.

Costly traits seem like a contradiction in terms, but the mechanisms by which they can evolve become clear when evolution is modeled mathematically (, ). There is evidence that mental disorders may have evolved as costs of attractive mental traits (); one in particular, bipolar disorder (a.k.a. manic-depression), fits this hypothesis quite well.

Ironically, a key contributor to the mathematics used to understand costly traits, George R. Price (), might have suffered from severe bipolar disorder. Most of Price’s work in evolutionary biology was done in the 1970s; toward the end of his life, which was untimely ended by Price himself. For many years he was known mostly by evolutionary biologists, but this has changed recently with the publication of Oren Harman’s superb biographical book titled “The Price of Altruism: George Price and the Search for the Origins of Kindness” ().

Bipolar disorder is a condition characterized by disruptive mood swings. These swings are between manic and depressed states, and are analogous to the movement of a pendulum in that they alternate, seemingly gravitating around the "normal" state. See the figurative pendulum representation below, adapted from a drawing on Thinkquest.org.

Bipolar disorder is generally associated with creative intelligence, which is a very attractive trait (). Moreover, the manic state of the disorder is associated with hypersexuality and exaggerated generosity (). So one can clearly see how having bipolar disorder may lead to greater reproductive success, even as it creates long-term survival problems.

On one hand, a person may become very energetic and creative while in the manic state. This could be one of the reasons why many who suffer from bipolar disorder have fairly successful careers in fields that require creative intelligence (), which are many and not restricted to fields related to the fine and performing arts. Creative intelligence is highly valued in most knowledge-intensive professions ().

On the other hand, sustained acute mania or depression are frequently associated with serious health problems (). This is why the clinical treatment of bipolar disorder often starts with an attempt to keep the pendulum from moving too far in one direction or another. This may require medication, such as clinical doses of the elemental salt lithium, prior to cognitive behavioral therapy. The focus of cognitive behavioral therapy is on changing the way one sees and thinks about the world, particularly one’s “social world”.

Prolonged acute mania, usually accompanied by severely impaired sleep, may lead to psychosis. This, psychosis, is an extreme state characterized by hallucinations and/or delusions, leading to hospitalization in most cases. It has been theorized that depression is an involuntary compensatory adaptation () aimed at moving the pendulum in the other direction, out of the manic state, before more damage ensues ().

Elaborate approaches have been devised to treat and manage bipolar disorder treatment that involve the identification of mania and depression “prodromes” (), which are signs that a full-blown manic or depressive episode is about to start. Once prodromes are identified, cognitive behavioral therapy techniques are employed to prevent the pendulum from moving further in one direction or the other. The main goal of these techniques is to change one’s way of thinking about various issues (e.g., fears, pessimism). These techniques take years of practice to be used effectively.

Identification of prodromes and subsequent use of cognitive behavioral therapy seems to be particularly effective when dutifully applied with respect to manic episodes (). The reason for this may be related to one interesting fact related to bipolar disorder: manic episodes are not normally dreaded as much as depression episodes.

In fact, many sufferers avoid taking medication because they do not want to give up the creative and energetic bursts that come with manic episodes, even though they absolutely do not want the pendulum to go in the other direction. The problem is that, if depression is indeed a compensatory adaptation to mania, it seems reasonable to assume that extreme manic episodes are likely to be followed by extreme episodes of depression. Perhaps the key to avoid prolonged acute depression is to avoid prolonged acute mania.

As someone with bipolar disorder becomes more and more excited with novel and racing thoughts (a prodrome of mania), it would probably make sense to identify and carry out calming activities – to avoid a fall into despairing depression afterwards.