Why Is It So Hard To Get Fit?

Everybody wants to be fit, at least to some extent. And there are good reasons for that. An athletic and muscular body is not only more pleasant to look at. It is also healthier, more functional, and more useful in general.

But how many of us actually manage to accomplish their fitness goals? Everyone who started a new diet or training program knows how easy it is to see results at first. However, after some time, progress slows down and eventually plateaus. Try harder and you might even start going backward.

Why is that? What is it that makes it so hard to get fit and to stay fit? Could it be that our body hates us so much? Actually, our body doesn’t hate us at all. If anything, it’s the exact opposite. The only problem is that our fitness goals of having more muscles and less fat, and our body’s goals of keeping us alive, might not get along very well. And the funny thing is that, from an evolutionary standpoint, it all makes a lot of sense.

Evolution and Genetics

If there is one thing our body is really good at, it must definitely be adaptation. For the vast majority of their time on Earth (∼4 million years), human beings have been hunter-gatherers. Meaning, our ancestors obtained most of their food by collecting wild plants and pursuing wild animals. Fast forward to the modern days and things have changed dramatically. Our modern lifestyle is completely different from the way people lived in the past. However, relatively speaking, its advent is actually very recent.

To notice the first significative change, we have to wait until the agricultural revolution, which “only” occurred ∼10,000 years ago. The second major milestone is the industrial revolution (∼300 years ago), which brought even more dramatic changes. If we do the math, this means that our genes adapted for over 99.5% of the time to the hunter-gatherer lifestyle and only for the remaining 0.5% to our modern lifestyle. On an evolutionary scale, this is comparable to the blink of an eye. Our genes have barely had the time to realize something happened.

However, despite their relatively recent advent, the agricultural and industrial revolutions have dramatically changed the environment around us. Our eating habits changed along. New technologies, animal husbandry, highly processed foods, pesticides, colorants, preservatives, unprecedented food abundance. Our dietary habits have changed too much, too quickly and too recently for our genes to keep pace.

As a result, we have a genetic makeup almost identical to the one of our ancestors, yet we live in a completely different environment. Different foods, different habits, and different priorities. But what do our ancient genes think of our modern day fitness goals? Are they open-minded and collaborative, or do they frown upon our projects and impede our efforts in every possible way?

The Importance of Being Fit

Is it so important to be fit? Depends. Firstly, it depends on what we mean by “fit”. Secondly, and more importantly, it depends on what our body thinks is important for us.

To put things in perspective, we must never forget our genes have a certain age. They have been through a lot and for a lot of time. They are true war veterans. Always in the trenches, always fighting to survive. As a consequence, their approach to life is very conservative.  The genes have taught the body that the most important thing is to keep us alive. Preferably, long enough to have children and pass on our genetic code. This ensures the survival of the species and, to our body, everything else is pretty much secondary.

When the body wondered how to accomplish this goal, the genes explained that energy is the most important thing. Every day, we need a certain amount of energy to perform all our activities and, more importantly, to stay alive. The body immediately realized two things were needed to get the job done. Number one, enough food. Number two, a way to store energy in case food becomes unavailable.

And this is where body fat comes into play.

Body Fat and Survival

Fat is the best way to store energy in our bodies. It is natural, space-saving and cost-effective. It doesn’t take much energy to be maintained and provides a lot of energy when burned. Also, if needed, new fat cells can be synthesized to hold a virtually unlimited amount of calories.

It’s easy to see why the body likes it so much. From the body’s perspective, energy means life. So, if food becomes unavailable, the more fat we have stored, the greater our chances to survive before we find some food again. Additionally, fat helped to keep us warm during winter. Back then, this was a pretty big deal. In non-tropical regions, people would fatten up in the summer when food was available to get through the winter. For all these reasons, the body will always offer very small resistance to the building of new fat cells.

This makes sense because, during most of our evolution, being fat has never been a problem. If anything, it’s the exact opposite. More fat stored meant a higher chance to survive. Overweight and obesity, if even possible, were less of a concern with winters and famines always around the corner.

On the other hand, losing weight has always been a hassle for the body. While physiologically able to adapt to both overfeeding and underfeeding, it will react much harder when underfed than when overfed. Dropping body fat, especially below a certain level, will put the whole system in a state of alarm. Let’s see why.

Leanness and Survival

In the scenario we just described, it’s easy to understand that leaner people were at a bigger disadvantage if compared to their fatter peers. In circumstances of severe food restriction or total starvation, a leaner individual has simply less fuel in the tank. Conversely, people who could store fat quicker and lose it slower were more likely to survive and pass their genes down the line.

Additionally, even if weight loss regularly occurred, the body considers losing it acceptable only up to a point. The reason being is that the body is not able to tell the difference between dieting and starvation. It only knows that we are eating less than we need.

This puts the system in a state of alarm. In the attempt to contain the problem, the body adapts by triggering a host of well-developed psychological and physiological mechanisms. Increased hunger and appetite, lowered energy and vitality, impaired immune response and sex drive, etc. And the symptoms exacerbate as we get leaner.

All this because, to the body, extreme leanness is incompatible with survival. When food becomes unavailable, it will gradually shut down every non-vital system in the effort to keep us alive. Ironically, this includes the metabolic system. Once turned off, metabolism slows down hence we consume less and hold on to body fat more. The exact opposite of what we want.

To add insult to injury, fat storage enzymes tend to increase along with increased fat storage capacity. This means the body is ready to put fat back on at an even accelerated rate. While it’s there, it will also add an arbitrary amount of extra weight. Just to play it safe. But then what about muscles? If life was so tough, we must have needed big muscles to hunt, run and fight. Right?

Muscles and Survival

It’s nice to imagine prehistoric men as massive, muscular and athletic. However, the reality is that probably they used (or had to use) their bigger brains to outsmart animals instead of relying on their relatively smaller muscles.

So while a reasonable amount of muscles was presumptively not only useful but necessary to survive in the wild, and the average prehistoric man is thought to had been fitter than the average modern man, an excessive amount of muscle mass was probably more harmful than good. And again, from an evolutionary standpoint, this makes a lot of sense.

Compared to body fat, muscle mass requires a lot more energy to build and to maintain. Additionally, more muscles are equal to more weight to carry around, hence further energy to spend. In other words, anything more than the bare minimum needed to walk around and get some food is dead weight the body will always be happy to let go.

However, this doesn’t that muscles are useless. It simply means that our body will painlessly allow us to develop new muscle mass, but only up to a point. Beyond that point, it will gradually hamper the building of new muscles and plot to get rid of them at the first opportunity. It doesn’t matter if we add an excessive amount of muscle mass or lose an excessive amount of body fat. If we push our body’s limits, we run into an equally difficult set of adaptations.

Lean or Muscular?

To make our lives even harder, our bodies are not very good at doing multiple things at once. Especially when these things are mutually exclusive and have opposite requirements.

Coincidentally, building muscles and burning fat happen to meet these criteria! Specific requirements for gaining muscles also inhibit fat loss while stimulating fat gain at the same time. Conversely, specific requirements for fat loss also inhibit muscle gain while stimulating muscle loss at the same time.

This has serious implications for athletes, like me and you, who want to be muscular and lean at the same time. Number one, synthesizing new muscle mass requires a lot of energy. This means we need to be in a caloric surplus. However, even if we diet correctly, part of the surplus will inevitably end up in the fat tissue. Number two, it doesn’t matter if muscles provide less energy than fat. The body will always break some muscle mass down when we diet.

Partly, this is due to the high metabolic cost of muscles which is hard to sustain during caloric restriction. Partly, to the increased reliance on proteins for fuel with less fat and glucose available.

Bad News for Women

Women love to be reminded how important they are, and we all must agree they are important indeed. From an evolutionary standpoint, in particular, they are so important to be ultimately responsible for the survival of the species.

Women give birth and take care of the children in their early stages of life. From the moment a woman gets pregnant to the moment she stops breastfeeding, a symbiotic relationship with her baby takes place. As long as this relationship lasts, her child is totally dependent on her. This means if the mother can’t survive, even the child won’t survive.

For this reason, their body evolved to adapt better to the absence of food, where better means faster and harder. As a consequence, women tend to have an even harder time losing weight and keeping it off long-term. Women also tend to have more problems with muscle loss, not to mention lower body fat mobilization.


Getting fit is not an easy job. It doesn’t matter if our goal is to get lean, muscular or both. Either way, we are literally fighting against millions of years of evolution.

Our bodies want to keep us alive more than anything. Unfortunately, for historical reasons, being fit, lean and muscular is generally not consistent with that goal. Actually, increasing muscle size and reducing body fat are towards the bottom of our body’s list of priorities. So much so that, beyond a certain point, it will actively work to prevent them from happening.

The body doesn’t know that our fridge is always full and obesity is a leading cause of mortality. It still thinks that we live in a cave and every day we have to fight to survive. In this scenario, being small and fat is beneficial, because it has always meant greater survivability. In a few thousand years, maybe, our genes will eventually figure out what the real problems are. Until then, a smart approach to training and nutrition remain the best way to achieve our fitness goals.

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