By Sten van Aken | Reading Time: 11 minutes

In the previous part of the ad libitum series (see Part I & Part II) we went over how the complex interplay between feedback systems causes us to play a game between cat and mouse that is very hard to win. In this piece, we’re going to try and outplay the cat by outsmarting the very systems that keep us alive.

The previous part gave you a general impression of the various ways in which the body adapts to change. Since we got an impression of the impact of the saucepan and its complexity, this article will go into depth about the fundamental principles of food characteristics and on how to use strategies in such a way that we can stay ahead one small step. To beat the change, is to be the change. This starts by outsmarting the piece of meat you inhabit, that is of course, your brain. This all starts by understanding the role of energy density in your diet.

Ad libitum Dieting III: Energy Density of our Food & Appetite Regulation

Introduction & Terminology

To get a better understanding of energy density, we need to emphasize the biological lens through which we viewed our eating behavior previously in part 1 of the ad libitum series.

To further support the terminology and red line of this article, ‘’calories’’ will always refer to the measurement we most often use to express energy in food, that is kilocalories (kcal) and not kilojoules (Kj). For the means and purposes of this article, we’re going one step further – or really the way it is commonly expressed in the scientific literature: kcal/g.

Energy density is most often expressed as the amount of energy that food has relative to its weight, in the case of the literature per gram.^[1]Poppitt, SD. (1995): Energy Density of Diets and Obesity. In: Int. J. Obes. 19 (Suppl.). URL: https://www.ncbi.nlm.nih.gov/pubmed/8581108. Thus, in order to determine the energy density of a food, we’d simply have to divide the amount of total energy by the total weight in order to end up at 1. Let’s start taking a general example how to calculate the energy density of a food.

A medium apple by USDA standards would weigh around 182 grams and have around 100 calories. Thus, in order to determine the energy density of the apple, we’d have to divide the total amount of energy by the total amount of weight. In the case of the apple, we’d have 100 kcal/182 grams which will give us an energy density of 0.88 kcal/g. Multiply this by a 100 and you have the amount that is found on a nutrition label. In a similar fashion, dividing the energy density of a portion size (say a 52 gram bar) one would do the same thing to end up back at 1.

Under the same token, two tablespoons (32 g) of peanut-butter (or 1, because literally anyone can fill 1 tablespoon with the unequivocal standard serving size of what we would consider 2) would give us around 180 calories. Thus, in this case we’re left with the equation of 32/180 which equals 5.63 kcal/g.

Apples and peanut butter are on the opposite side of the “energy density” spectrum. (Image Source: depositphotos / bhofack2)

Now pause for a second. Remember that saucepan we talked about in the previous issue? I don’t have to convince you there is more energy to be found in peanut-butter than there is in an apple – but what I do want you to notice is the quit significant energy discrepancy between these two foods. In the case of an apple and two tablespoons of peanut-butter, this means you can eating almost 6 times more food by weight.

It is this very large energy discrepancy that we’ll be hovering around to understand more about what type of feedback system(s) we’re dealing with and ultimately how we can use dietary strategies to beat the game

An alternative viable naturalistic lens

We normally look at dieting through the lens that resembles the food pyramid we’re familiar with, such as the one popularized by Eric Helms in his book(s) Muscle & Strength Nutrition Pyramid.^[2]Helms, E. / Morgan, A. / Valdez, AM. (2019): The Muscle and Strength Pyramid: Nutrition. Available at Amazon.com.

The popular Muscle & Strength nutrition pyramid by Helms ranks the most important nutrition variables according to their priority. The more important the factor the further down it is placed in the pyramid. For example, if you want to create a diet plan to successfully lose weight (or build muscle), it makes no sense (or at least not much) if you worry too much about things like nutrient timing or supplements, unless the lower levels of the pyramid have been already aligned according to your goals. (Graphic Source: Helms & 3DMJ, 2019)

However, to say that the natural law that dictates weight loss is the same that goes for largely subjective feelings of appetite – is to say the least – problematic. As will become clear in later parts of this article, the fact that some macronutrients are more satiating than other macronutrients has far less to do with the fact that they’re macronutrients and far more about certain characteristics that come with those macronutrients.

So we took the two tablespoons of peanut butter and a medium-sized apple as an example of typical foods. But this is hardly useful how a typical diet would look, which would inevitably (I hope) be more than just apples and peanut-butter. If we looked at dieting through the same lens we get an unique perspective. Let’s start with that typical male we used in part 1 that needed 2500 kcal per day.

If we were to look at the total amount of fat one could eat if one were to consume 2500 calories, we would end up with a total amount of 278 grams of fat (278 * 9 kcal = 2502 kcal). So technically you could meet your energy demands with as little as 278 grams of fat. This of course changes if we choose for an amount that resembles sometimes we’re more familiar with in a diet – a combination with proteins and carbohydrates.

Protein and carbohydrates respectively contain 4 kcal per gram. Thus, by definition, we can already have twice as much as carbohydrates as well as protein if we were to choose either one of macronutrients to fill up our diets completely. In the context of a 2500 kcal diet that means we can either choose to have 625 grams of protein or carbohydrates. This is a very large difference, not only in a relative sense (625 is more than twice that of 278), but also in a practical sense (you get to eat twice the amount of food).

The difference between food with low and high energy density in regard to volume. (Graphic Source: healthcare2966412240)

Now that we’ve have an impression of how a diet could look through a different lens, we can zoom out and revert back to the more ‘practical’ side of nutrition. That is, we eat foods that are part of individual and/or collective food groups. Fruits, grains, vegetables, legumes, nuts, fish and meat – you name it. Thus, we’re bound to the characteristics that come with the foods we eat. But rarely do we really look past what we see – both literally as well as figuratively. Through the same practical lens, very rarely do we actually look past the label – and dare to wonder what it really is that makes a food either satiating or not.^[3]Holt, SH., et al. (1995): A satiety index of common foods. In: Eur J Clin Nutr. URL: https://www.researchgate.net/publication/15701207_A_Satiety_Index_of_common_foods.

Satiety index (mean values ± SEM) of various tested foods in relation to the reference food (white bread). (Graphic Source: Holt et al., 1995)

So what is the exact system, if anything that looks close to the food pyramids we’re familiar with?

Simple explanations for vague concepts

Although there is agreement that healthy foods should make up the majority of someone’s diet, reasons for this advice are often vague and not directly based on scientific evidence. For example, foods are often described as ‘’processed’’ or as ‘’a source of vitamins and minerals’’ without adequate explanation why these characteristics deserve the amount of attention they’re currently having.

In a similar fashion, foods are often labeled as ‘’good’’ or ‘’bad’’ on the basis of its macronutrient profile or if its natural or not – but here too, people limit the amount of characteristics that one deems (ir)relevant.

Where both descriptions attempt to classify foods on certain characteristics, both fail to give adequate or even reasonable explanations why certain characteristics are important and thus why we choose certain foods over other foods. The next topic doesn’t need an introduction, yet here I am pointing something out everybody knows but forgets to consider in his diet: water and the bound(s) it shares with and through proteins, carbohydrates and fats.

Water has, to no one’s surprise, no energy. The importance of water in food is pretty obvious, but gets ignored because it can be found everywhere and is rarely a scarce resource since we’re able to support our body by ad libitum consumption (e.g. drink when you’re thirsty, stop when you feel satiated).^[4]Cotter, JD., et al. (2014): Are we being drowned in hydration advice? Thirsty for more? In: Extrem Physiol Med. URL: https://www.ncbi.nlm.nih.gov/pubmed/25356197.

However, for this very reason not much attention is paid to its significance until we ourselves are deprived of it, since it plays such a critical role in our existence. However, in a Western sense one rarely gets exposed to situations of absolute deprivation of food and water. What does seem to ring more bells is the amount of processing. To see how this comes into play in our next piece as it will play a critical role in energy density, I’m going to further provide examples so you get into my train of thoughts. Let’s start with one of the most satiating yet most controversial  foods of all time: (white) potatoes.^[5]Holt, SH., et al. (1995): A satiety index of common foods. In: Eur J Clin Nutr. URL: https://www.researchgate.net/publication/15701207_A_Satiety_Index_of_common_foods.

What makes potatoes so filling?

Potatoes are, if solely cooked as they are, 79% water and 17% carbohydrates, while only having 0.1% fat.^[6]USDA.gov (2019): Potatoes, boiled, cooked in skin, skin, without salt. URL: https://fdc.nal.usda.gov/fdc-app.html#/food-details/170439/nutrients. On the other side of the spectrum, nuts are roughly 4-6% water and 65-75% fat.^[7]USDA.gob (2019): Nuts, walnuts, english. URL: https://fdc.nal.usda.gov/fdc-app.html#/food-details/170187/nutrients.

Nuts are not subject to a lot of change since they have little to change but burn, having little to no water to lose. Potatoes on the other hand, if roasted or deep fried, have far more to lose and thus are far more subject to change, allowing them to shrink down until they’ve lost the majority of their water content. This inevitably leads to an increase in energy density, since water thus makes up the majority of volume in your diet. Vice versa introducing bulk vegetables in your diet does the opposite. Indeed, one must sometimes ask the question if it really is all about fruits and vegetables, or if it really is the water we’re talking about.

Energy density (in kJ/g and kcal/g) and water content (g/100g) of selected foods. (Graphic Source: Drewnowski, 2003)

If we go back to our earlier example where we pointed out that we can already consume more than twice the amount of carbohydrates and protein than fat, this is further enhanced by the fact that some food groups that are of carbohydrate origin often come with far more water. The same is true for protein.

The opposite is often true for fats, since they exist in our diets in mostly a processed refined state, that is exclusively the oil, and less likely as a fruit like avocado or as (pea)nuts which have some, but really very little water. This ultimately presents us with the paradox that is energy density, where what someone means when one considers energy density in the diet is actually the amount of processing. But what it lacks is the correlation with the feedback systems we talked about.

Correlation between the energy density and the fat (A.) and carbohydrate (B.) content of various foods. (Graphic Source: Drewnowski, 2003)

Correlation between the energy density and water content of various foods.(Graphic Source: Drewnowski, 2003)

The relationship with the feedback systems

Take the example of thirst – which I would argue is the best way to see how the feedback systems are intertwined in the most extraordinary way, for the simple reason that it is the very substance we can do least time without and are confronted with on a daily basis. This all starts with the familiar signal called thirst.

You’re thirsty. You take three good sips of sparkling water with that giant forearm of yours, pause it for a couple of seconds, and then down the glass like the total champ you are.

What people normally assume is that thirst is the signal for dehydration and/or the necessity of/for fluid. However, if we were to look at what happened from a physical point of view, the liquid spent less than a totality of 10 seconds in your mouth and went down your esophagus into your stomach while some managed to spill over into your small intestines. But the fluid you drank is nowhere to be found in your blood. Yet the sensation you called thirst 30 seconds has yet to resurface because it is nowhere to be found.

The same reason thirst is gone within seconds, the hunger that struck you earlier already partly subsided during preparation and totally vanished 10 minutes after you ate your meal. In the same way as the liquid, it spent less than a totality of 5 minutes in your mouth and will be carried as a food baby for the next of hours before it is passed through the remaining parts of the digestive tract as a miscarriage.

So, contrary to a lot of processes, the real question to ask is why we get hungry in the first place. Indeed, it is actually the brains’ interference by making predictions focused on meeting needs like sleep, hunger, thirst and warmth that used to lead to positive reward-driven dopamine surges and ensured the survival of our species. Yet despite societal pressures shaping our thinking, these fundamental biological facts are still shaping our (mal)-adaptive behaviors in the 21^st century.

Food can be divided into four categories of energy density (ED; kcal/g) in order to allow for control in the selection of foods and portion sizes. (Graphic Source: Rolls, 2017, adapted from Rolls, 2014)

Putting it all together

In part 1 we’ve learned that for centuries we’ve met our needs the same way all biological organisms living on this planet have. However, we also learned that we as humans eat for a variety of other reasons to meet our biological need, which presents its unique facet of problems in our 21^st century food environment.

Later in part 1 we learned that diets that are higher in energy don’t always necessarily lead to better outcomes in terms of weight loss, even when combined with exercise – as well as diets that can be more satiating per Calorie. Furthermore, we also clued in on dietary trials where calorie-focused diets are found to be more effective in the short-run, while trials focusing on impacting the/our senses/feelings/signals are more sustainable in the long run by keeping the weight off and meet keeps our brains happy.

In part 2 we learned that no matter what we throw at the system, there is always an (alternative) mechanism by which things come flying right back flying at ya. This was discussed by talking about purple ringworms surfing rainbows and rodents having implanted weights in them that point to various systems that regulate body weight independently of leptin.

Furthermore, we talked about the interactions between the tub, pan and sink and how the game has a lot in common with the cat and mouse game that is almost by default hard to win.

Forest plot of a meta-analysis that took into account studies (RCTs & cohort studies) that examined the effects of the energy density of the food consumed in terms of a change in body weight in overweight study participants. The squares represent the point estimate of the intervention effect for each study. The horizontal lines connect the lower and upper limits of the 95% CI of this effect. The area of the shaded squares reflects the relative weight of the study in the meta-analysis. Diamonds represent the mean difference of the subgroup and the pooled mean differences. (Graphic Source: Stelmach-Marda et al., 2016)

I promised I’d give you strategies in this one, but upon writing it wanted to give you more examples of the irony of the signals we live with by the day and that it is to understand that the mind is a weird thing. This issue gave you a couple of clues as to what these signals really are, if anything, and gave you clues as to what might be a more important factor to consider when setting up a diet, that is energy density.

The next issue is going to be a bomb of practical research regarding the various studies that manipulate energy density in both short- and long term studies and how circumstances (as you understand by now) like physical health play an important role in the strength of the various short- and long term feedback systems.

Thanks for tuning in with me. See you next time.

Title Image Source: depositphotos / netfalls