We all know that we can lose weight by eating less calories. When the body uses more energy than it is taking in, this result in fat loss. A deficit of 3500 Kcal of energy will result in one pound of weight loss. However, many people who do successfully lose weight end up struggling to prevent weight gain. They need to stick to a low calorie diet and have to tolerate being hungry all the time.
But many people won’t put up with this struggle, they may moderate their calorie intake a bit and as a result they end up not losing enough weight. Having to tolerate discomfort in order to be at a healthy weight doesn’t sound like a natural state for the human body. Surely there must be a more natural way to achieve a healthy bodyweight? In this blogpost I’ll dig deeper into this issue to see where the real problem lies. This will then suggest far better ways to tackle the problem.
This rather long-winded blogpost is organized as follows. In the next section I’ll consider the energy balance aspect of weight loss. This will lead to the insight that fat tissue influences metabolism. I’ll then present another argument based on evolution that corroborates this.
To get to better ways to lose weight, we must find factors that influence the way the fat tissue affects metabolism. The arguments that can lead us to the answer will again be based on evolution having led to a robust body design. I’ll then first explain why we can trust these sorts of argument.
I then conclude this blogpost by identifying the main properties of a diet and lifestyle that should lead to a healthy bodyweight without having to stick to an energy restrictive diet. Impatient readers may want to jump ahead to that section straightaway.
The fundamentals of weigh gain and weight loss
So, we know that eating less calories will cause weight loss, it’s then tempting to think that eating too many calories is the cause of being overweight. But that’s false! What is true is that eating more calories than you burn will cause weight gain. But once you are at a certain weight and you are not gaining or losing weight, you are burning as much energy as you are absorbing from your diet.
Example: Jane wants to lose weigh
Suppose that Jane is overweight, she weighs 220 pounds while 175 pounds is her ideal weight. She is now eating 2500 Kcal a day and not gaining or losing any weight. A 1700 Kcal diet will bring her at her target weight in about 7 months time. But she wants to avoid the burden of being in calorie deficit and having to fight off your body’s tendency to move back to her old weight. So, we need to ask why Jane can’t be at 175 pounds while eating 2500 Kcal.
Jane’s body mass of 220 pounds can be considered to be the sum of 45 pounds of excess fat she wants to get rid of and the 175 pounds she wants to keep. Now fat has a metabolic activity of 2 Kcal per pound per day. So, Jane’s body minus the 45 pounds worth of fat tissue is actually using 2410 Kcal a day. Part of this energy use comes from the burden of having to carry 45 pounds of weight.
Now, this burden of carrying that excess body fat can be replaced by exercise once Jane is at her target weight. And that exercise is what she is already doing now by carrying her excess body fat, so this won’t require gaining physical fitness. So, it should in principle be possible for Jane to weigh 175 pounds and still eat about 2400 Kcal by exercising more. Nevertheless, the fact that people tend to regain their weight when they stop dieting, suggests otherwise. What’s the problem?
Why does overweight Jane have a faster metabolic rate than slim Jane?
What’s the difference between Jane weighing 220 pounds with 45 pounds excess fat and Jane having lost 45 pounds of weight, carrying a rucksack weighing 45 pounds all day long as exercise? Why can she eat 2500 Kcal with no weight gain in the former case while in the latter case she’ll gain weight until she’s back at her old weight?
The difference can’t be explained by the 90 Kcal energy use of the 45 pounds of fat tissue. Muscle tissue uses 6 Kcal per pound per day at rest but much more during exercise. After exercise muscle tissue will also use more energy which is needed for recuperation. While this is known to play a role when people have lost a significant amount of muscle mass, people experience problems maintaining their new weight regardless of muscle mass loss.
Fat tissue influences metabolism
There is then only one possible explanation left. Fat tissue must influence the metabolism, more body fat causes the body to rev up the metabolism. How can this work? It is known that fat cells produce hormones. If fat cells become full, they the produce the hormone leptin that will suppress hunger. This hormone was only discovered in 1994. Since then other hormones produced by fat cells have been discovered:
Some of these hormones influence metabolism, they have been discovered only in the last few years. So, it’s quite plausible that there are many more such hormones to be discovered. Now, we arrived at the conclusion that fat tissue is involved in regulating metabolism by invoking the fact that people tend to regain their old weight after weight loss if they stop dieting. Let’s consider a more powerful argument based on evolution that can guide us to find the right diet for weight loss.
Human beings are warm blooded mammals. Our bodies constantly burn energy at quite a fast rate. Clearly mammals could only have evolved under circumstances where food is not scarce. However, there are always fluctuations in the amount of food an animal is able to find. This requires the animal to have sufficient energy reserves.
It’s then also necessary to regulate the metabolic rate to make sure the energy reserves won’t get depleted or won’t grow out of bounds. Without such a regulatory system, an animal could starve to death if it had to expend just a little amount of energy more to find its food, or become extremely obese due to eating just a little more and becoming just a a little less active.
Suppose for example that we would expend 150 Kcal a day more and eat 150 Kcal a day less. Then that’s a deficit of 300 Kcal per day, causing us to lose 1 pound of body fat in about 12 days. If this were to go on indefinitely, we would eventually starve to death.
Fat tissue modulates metabolism to keep energy reserves stable
It’s just not plausible that warm blooded organisms could have evolved without a feedback mechanism that modulates the metabolic rate depending on how much energy reserves the animal has. So, if fat cells are full, the metabolic rate should be higher than when they are empty. This way the energy balance is stabilized on the long term and large fluctuations in the bodyweight are prevented.
But this then seems to imply that the amount of fat reserves is fixed at some level. However, evolution will have led to a mechanism that regulates the metabolic rate, so that animals can survive large shortfalls of food for long enough. This then translates into some setpoint for the amount of body fat, which in turn is determined by other factors that determine how much body fat is necessary to survive for some time without food.
We can then speculate about these other factors based on the idea that evolution should have led to a well designed, robust body. But since we’re then going to run way ahead of the science, let’s first consider how reliable we can expect such arguments to be.
Robustness of living organisms
When we go about our usual business, we tend not to consider that we are extremely complex self-maintaining machines. This is not how we perceive our own body. Our self-image when taken literally is overly simplistic. In our minds our bodies are simple machines that we use in our daily lives, like cars or refrigerators. To get an idea of the real complexity of life, let’s watch this short excerpt of a video by Jack Szostak on the origin of life:
So, each cell in our body harbors an enormously complex biochemical machinery. One cannot compare a single cell with a machine like a car. A single cell is more similar to the set of all machines in all factories in a small country. At that level there are regulatory mechanisms like managers of companies, a political system, there exists an economy that feeds back on how the factories are operated.
This extremely complex system has been shaped by evolution to optimize the physical properties of the body as a whole needed for survival. We should thus expect living organism in their natural environment to be extremely robust systems.
Algorithmic view of life
The biochemical machinery in our cells implements algorithms that make our body function in a very robust way. We’re able to deal with many problems that can arise within a broad range of natural conditions. A perturbation away from an ideal condition will trigger a reaction that will counteract that perturbation. Each cell in your body is constantly at work maintaining the right conditions. The collective effect of all the actions by all cells in an organ make that organ function in the right way, and all the organs in the body make the entire body function as a robust system.
The enormous complexity of the biochemical machinery in each cell originally evolved to let microbes survive in a challenging environment. When multicellular life evolved, part of this complexity could be used for the benefit of the organism as a whole. Evolution has optimized the available cellular machinery into useful tools for the organism it is part of. This has then led to organisms that are very adaptable to challenging environments.
The four zones of life
A perturbation away from an ideal state will lead to lots of biochemical processes that will undo the effects of the perturbation. The stronger the perturbation, the more urgent it becomes to counteract the perturbation. However, any organism will have physical limits to what it is able to deal with. This means that up to some limit, it will be able to respond to stronger perturbations with with faster and more elaborate restorative processes. We can schematically illustrate this using the following diagram:
In the green zone, the organism is close to its ideal state, but there can still be significant perturbations here that are dealt with vigorously. In the orange zone the internal state of the organism has been compromised to such a degree that this affects its ability to deal with additional perturbations. The organism is then in an unhealthy state. It may then resort to stronger restorative actions that in the green zone would not be taken. It may e.g. react with an inflammation to an infection when that same infection in the healthy green zone would not have led to an inflammation.
In the red zone, the health of the organism is so bad that it’s going to die on a short time scale unless it is able to move to the orange zone. A movement into the red zone will trigger very strong biochemical responses to steer the organism back to safety.
For example, if the organism is deprived of oxygen, it will gasp for air, it will do everything it can to move as fast as possible to the orange zone. If it is unable to do that, its biochemical machinery will get damaged beyond its repair capability. It will then end up in the black zone which corresponds to the dying or dead state.
Maintaining optimal health and fitness in our modern society
The problems many people have with weigh loss seems to contradict the robustness of the human body. While we have seen that we can explain many of the problems people experience with controlling their weight from the point of view of robustness, the setpoint for the amount of body fat seems to be too high. The explanation for this can only be that our lifestyles in our modern society is too far removed from the natural lifestyles our bodies have evolved to adapt to.
What are then the relevant differences between the modern diet and the diet our bodies have evolved to eat? As I’ve pointed out in this comment in the British Medical Journal, a very important difference between the modern diet and a diet based on whole foods, is the amount of fiber and certain minerals like magnesium.
High ratio of fiber and magnesium to calories in whole foods
It turns out that the ratio between fiber and calories is remarkably similar for many of the natural energy rich foods. Even when comparing foods rich in fats like nuts to foods rich in carbs like potatoes yields a similar order of magnitude.
Getting 2500 Kcal should then yield at least 70 grams of fiber, which is way more than the RDA of just 40 grams, which in turn is way more than the 20 grams most people get. By not getting enough fiber, we deprive our intestinal microbes of enough food, so we end up with a microbiome that’s not as robust as it should be.
For the mineral magnesium, which is known to play an important role in metabolism , the same is true. Getting 2500 Kcal from natural foods should yield at least 0.7 grams, which is almost double the RDA, while most people get a lot less than the RDA.
Eliminate refined fats and sugars from the diet
The reason why most people end up eating way less than than the natural amounts of fiber and magnesium, is because a significant fraction of the calories in modern our diets comes from refined fats and sugars. This causes us to eat far less of the natural sources of energy that contain fiber and magnesium.
The key to getting to a healthy body weight is thus to get the calories from the natural sources. But because fat and sugar are extremely compact sources of calories, this requires getting used to eating vastly larger volumes of food. A change to a natural diet has to be done gradually, not just to get the body chance to get used to the large volume of food, but also to get used to the far higher fiber content of the diet.
One can then ask why eating more fiber and magnesium will cause the setpoint of the amount of body fat to be set to a lower value? I’ll answer this question in the next blogpost. I’ll also discuss the effect of exercise and proper sleep on the bodyweight.
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