Monday, November 26, 2012

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.

11 comments:

J. Stanton said...

This concept (upregulation/downregulation) most likely underlies the success of cyclical ketogenic diets...and the short-term success most people experience on any diet sufficiently different from their current diet.

The importance of the fact that "palatability" is a subjective judgment, based on one's individual nutritional state (and cultural context), cannot be overstated. For a real-world example of your simulated data, instrumented to the point of measuring neural firing rates in response to salt ingestion, see Aldridge et.al., which I cite in this article.

(I look forward to returning to this topic once my AHS 2012 talk is available on video! Unfortunately, I'm among the majority of presenters still waiting.)

"Modern engineered foods are designed to bypass reward mechanisms that match nutrient content with deficiency levels."

It's worthwhile to note that they do so not by being excessively palatable: Wheat Thins aren't more palatable than bacon-wrapped filet mignon! They do so by having tastes we associate with nutrition, without containing actual nutrition.

Example: MSG (and "hydrolyzed corn/soy/wheat protein") stimulates the taste receptors for umami (free glutamate). The richest sources of free glutamate available to Paleolithic humans were shellfish, meat, and fish. Therefore, MSG gives us the "meaty" taste of complete protein without actually providing any complete protein...so the deficiency of protein that causes you to crave umami will never be satisfied, no matter how much MSG-laden snack food you consume.

Thus, the much-abused concept of "hyperpalatability" has much more to do with lack of nutrients than excessive tastiness. As an exercise, try to find a "hyperpalatable" food that contains complete protein (we've eliminated all grain-based foods), natural fats (we've eliminated everything cooked in 'vegetable oil'), and significant vitamin/mineral/nutrient content (fortification doesn't count).

JS

Anonymous said...

Great post.

Do the isolines have any practical significance, though? I.e. why is it useful to find different combinations of deficiency and nutrient content that keep palatability the same?

Ned Kock said...

Hi JS. A person I know who’s struggling to lose body fat would probably disagree with this: “Wheat Thins aren't more palatable than bacon-wrapped filet mignon!”

Ned Kock said...

Hi Anon. In this post the isolines help make a point, but they can be very useful in a more practical sense in moderating effects analyses – e.g., levels at which a drug A maximizes the effect of another drug B on health, when A and B interact with one another (very common).

J. Stanton said...

Ned:

There are two concepts we need to not confuse with "palatability" -- because if we simply define "palatability" as "that which makes us eat", we've created a circular definition that doesn't explain anything. And I know you understand this: I'm going through it for your readers.

First is the difference between hedonic impact (palatability, "liking") and incentive salience (our drive to actually consume more, "wanting"). Bacon-wrapped filet has more hedonic impact than stale Wheat Thins -- it's more "palatable", and we "like" it more -- but since it's very satiating (due to containing lots of complete protein, among other nutrients), its incentive salience (our "want" for more) decreases rapidly as we eat it, and we soon stop eating.

In contrast, stale Wheat Thins are less palatable than bacon-wrapped filet -- we don't "like" eating them as much. But, since they're nutritionally empty, they don't produce satiation, and there's nothing to stop us from continuing to eat them -- as you point out, our body is still hungry for nutrients, and a combination of indigestible, incomplete protein, linoleic acid, refined starch, and refined sugar doesn't satiate our hunger.

Second, the drive to consume (incentive salience, "wanting") is modulated by the availability of food. Bacon-wrapped filet requires significant effort to cook, or significant time and money to go out to a restaurant and buy it. In contrast, all we have to do to get Wheat Thins is open the bag. So we don't have to "want" Wheat Thins nearly as much as we have to "want" bacon-wrapped filet in order to consume it! That's not palatability -- it's availability.

This is true of almost all whole foods: they're perishable, and they require preparation. As an exercise, try to find a "hyperpalatable" food that isn't either a non-perishable packaged food, or takeout food ("fast food").

JS

dearieme said...

To make the fasting phase more enjoyable, have a little drink. A glass of a dryish Madeira should be just the job, or a modest glass of Moselle.

js290 said...

Ned, you should recommend to your friend to follow Jimmy Moore's nutritional ketosis experiment.

Great stuff from JS as usual. As I responded to one of his posts in the past, food reward doesn't adequately explain why the energy from more rewarding foods would be preferentially stored rather than expended. And, if reward does bias the energy towards storage, how does that happen at the biochemical level?

"In contrast to the hormonal activation of adenylate cyclase and (subsequently) hormone-sensitive lipase in adipocytes, the mobilization of fat from adipose tissue is inhibited by numerous stimuli. The most significant inhibition is that exerted upon adenylate cyclase by insulin. When an individual is in the well fed state, insulin released from the pancreas prevents the inappropriate mobilization of stored fat. Instead, any excess fat and carbohydrate are incorporated into the triacylglycerol pool within adipose tissue."

Anonymous said...

awesome post & discussion as well.

thanks

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