Summary of the book "Why We Eat (Too Much)" - By Andrew Jenkinson

Key Concepts in this book:

1. The energy challenges of single-celled creatures were solved by a chance meeting.
2. Humans compensated for their large brains by sacrificing other organs.
3. Fire's discovery shaped our cultural and biological identities.
4. The life of the human body is dependent on the body's ability to self-correct hazardous aberrations.
5. Overeating causes us to burn gasoline at a faster pace.
6. Calorie limitation causes a decrease in metabolic rate.
7. Our weight is controlled by hormonal signals.
8. Obesity is a given in today's Western diet environment.

Who can benefit the most from this book:

• Frustrated dieters.
• Science lovers.
• Sugar addicts.

What am I getting out of it? Discover the truth about metabolism.

There's a lot of buzz about what we eat these days.

Some people believe that avoiding fats will lead to better health and happiness. Others recommend going vegan or eliminating carbohydrates from one's diet.

All of these so-called miracle cures boil down to one thing: depriving your body of calories.

That works — at least for a while. Dieters all over the world know that dropped pounds don't stay away for long. In fact, you frequently wind up gaining more weight than you did before you started dieting.

There has to be a more effective strategy to manage your weight and health. Andrew Jenkinson feels that skipping the fads and learning how your body's metabolism actually functions is the best option.

And that's exactly what we'll be assisting you with within the coming moments.

• You'll learn how single-celled bacteria moulded our metabolism four billion years ago.
• Why calorie restriction sets your body up for future weight gain.
• And how the war on "bad" fats spurred today's obesity epidemic.

1. The energy challenges of single-celled creatures were solved by a chance meeting.

Our narrative begins approximately four billion years ago when our planet was little more than a dark and turbulent tropical sea under an oxygen-depleted sky.

In this primordial swamp, simple carbon-based chemical chains floated aimlessly. Then, by happenstance, they discovered a formula for self-replication.

These replicants began by incorporating free-floating substances into their structures. They then divided those structures into two chains — a primitive version of DNA – and started making new carbon copies.

Earth's first life-form, the single-cell bacteria, debuted on the evolutionary stage after replicants become increasingly complex over time.

The main takeaway is that an accidental encounter solved the energy challenges of single-celled life.

The bacterium's DNA code – the formula that allows it to multiply – is contained within the protective wall of its cell. It has a single evolutionary goal: to grow and survive long enough to produce a new generation of bacteria. It does, however, require energy to accomplish this.

Early bacteria were extremely efficient in converting food into a source of energy that could be utilised by all of their cellular components. There was a definite limit to how much energy they could generate because they couldn't metabolize oxygen.

This ultimately inhibited the evolution of more complex living forms. Then, some three billion years ago, a new type of oxygen-processing bacterium appeared. Existing bacteria were efficient; this bacterium, on the other hand, was a force to be reckoned with. It sucked up massive amounts of food and produced energy on a massive scale.

Older bacteria were unable to compete. They didn't have to, fortunately. Rather, they ingested – but did not digest – the intruders who had now taken up residence within them. Both parties benefited from the arrangement. The first bacterium protected the second from predators while benefiting from its ability to generate large amounts of energy. In a nutshell, one cell invaded the other, and both thrived - a process known as endosymbiosis.

In today's world, the progenitors of these energetic upstarts can still be found inside the cells of every plant, fish, fungus, and mammal. All of these species get their energy from mitochondria, which are microscopic power plants. Life on Earth as we know it would be impossible without them; our cells can't produce enough energy to keep us alive on their own.

2. Humans compensated for their large brains by sacrificing other organs.

All living things, including snakes, mushrooms, birds, roses, and humans, are descended from a single-celled ancestor. That is to say, all of these species produce energy in the same manner.

How? Food is converted into energy by mitochondria inside cells, which is then stored in battery-like molecules called adenosine triphosphate or ATP. These molecules are life's currency. Viruses use them as well, albeit by hijacking the ATP of the cells they infect.

Because all creatures have a restricted number of cells, they must eke out a living and perform all of their essential functions while adhering to a strict energy budget. Every species has a budget, but some accountants are more inventive than others.

The main point is this: Humans compensated for their large brains by sacrificing other organs.

250,000 years ago, the first anatomically modern Homo sapiens appeared. The size of their brains distinguished them from Homo erectus, our first non-ape predecessors.

The brain is a gas guzzler in terms of energy consumption. It alone accounts for 25% of our daily calorie intake. So, how did we come up with the funds for such a costly organ?

The short explanation is that we had to make some cuts somewhere else. Let's dissect that.

The energy budget of every species is proportional to its size. The more cells an animal has, the more ATP-producing mitochondria it contains. The amount of energy required for survival in animals is determined by their weight. A 65-kilogram person, for example, requires far more energy than a 65-kilogram Saint Bernard. In that situation, they both require the same number of calories to maintain important organs and life-sustaining activities such as breathing.

Large primates have an energy budget that is the most similar to ours. Take gorillas, for example, who we'll suppose have unlimited access to food. Their organs are similar in size and weight to ours, and they can create roughly the same amount of energy that humans can. The most significant distinction is that human brains are around four times larger than those of these primates. Where are we going to get the extra energy?

The solution is in human stomachs, which are much shorter than gorillas' and hence use less energy. Both species have similar gastrointestinal tracts, but ours are shorter because we can do something gorillas can't: we can cook. We'll see how that skill shaped us into the people we are now in this next concept.

3. Fire's discovery shaped our cultural and biological identities.

Long before Homo sapiens arrived on the scene 250,000 years ago, prehumans evolved larger brains than other primates.

A million years ago, Homo erectus, for example, outsmarted chimps. Archaeological evidence reveals what they did with their enhanced brainpower: they honed their hunting skills and developed primitive tools. Slowly but steadily, they abandoned their primate counterparts' nearly vegetarian diet.

Humans, unlike other species, did not develop sharper teeth or stronger jaws when they developed into carnivorous predators; in fact, both grew smaller through time. Prehumans became more human as they ingested more meat.

To figure out why, we must examine not only what they ate, but also how they ate it.

The main point here is that the discovery of fire shaped humans culturally and biologically.

The Wonderwerk is a large cave complex located at the foot of a grassy hill in South Africa's Northern Cape province. Humans lived in these caverns for a long period. It was prehumans like Homo erectus who came before them. It was apes before them. It has been inhabited by huge mammals for around two million years.

Archaeologists discovered evidence in 2012 that Homo erectus began cooking with fire a million years ago in these caves. It turns out that fire was discovered far earlier than originally believed.

But why does this matter? To begin with, it indicates that cephalization – the growth of larger-than-average brains – occurred around the same time as the invention of fire cooking. This helps us understand how the human body was able to transmit energy from the gut to the brain.

Meat that has been cut up and cooked over an open fire is much easier to chew and swallow. Our forefathers didn't need to acquire sharp teeth or larger jaws because cultural and technical advancements had already taken care of the heavy lifting.

It's also simpler to digest roots and tubers when you use fire. Cooked foods have previously been "predigested," unlike raw foods, which need a lot of energy to convert into fuel. Cooking, after all, breaks down molecular connections and makes nutrients that are difficult to obtain more accessible.

Because they spend entire days consuming raw foods, which are more difficult to digest, gorillas have longer gastrointestinal systems than humans. Cooked meals are a far more efficient food-to-fuel conversion system. As a result, our intestines shrank, freeing up energy for a growing brain.

4. The life of the human body is dependent on the body's ability to self-correct hazardous aberrations.

We've followed the evolutionary path from single-celled bacteria to big-brained, meat-eating Homo sapiens thus far. The energy was our guiding thread.

However, before we can continue our investigation into how we make and use energy, we must first discuss negative feedback mechanisms.

Negative feedback is required by all systems. Consider a workplace. It follows a predetermined schedule - for example, it is open from 9 a.m. to 5 p.m. When this rule is broken, the system automatically corrects itself. When a manager reprimands a worker for being late, she is doing just that: her negative feedback realigns the employee with the system.

This is how our bodies work as well.

The main point here is that the human body's life is dependent on its ability to self-correct harmful aberrations.

A sensor and a switch are required for a negative feedback system. The sensor detects deviations and activates the switch, which returns the system to its original state.

The manager, at our office, was the sensor. When she noticed an employee arriving late, she gave a verbal warning, which acted as a switch to change that person's behaviour.

Negative feedback mechanisms exist in our bodies as well. Take care of your hydration. We're 70% water, and we can only operate if our water levels remain at that level. Dehydration causes dizziness, weakness, and, in the worst-case scenario, death. Overhydration is equally as harmful, as it can lead to deadly convulsions. As a result, timely self-correction is critical for survival.

Our hydration sensor is the kidney. It employs a hormone called renin to deliver messages to two switches when it recognizes that we've consumed too much or too little water. The first regulates thirst and, as a result, how much water we consume. The second controls the amount of water we excrete in our pee.

Let's pretend you don't drink anything for a half-day. This is detected by the kidney, which activates the first switch. A thirst signal is received by the brain, and all you can think about is getting some water. The kidney also turns off the second switch at the same time. When you're dehydrated, your urine becomes darker and more concentrated as your kidneys fight to conserve body water. Drinking too much, on the other hand, causes the thirst switch to be deactivated and urine production to increase.

The human body uses the same negative feedback system to control energy consumption, usage, and storage, as we'll see shortly.

5. Overeating causes us to burn gasoline at a faster pace.

Let's go over everything again. Negative feedback keeps our water levels in check by correcting two potentially catastrophic errors: overhydration and dehydration.

Of course, water isn't the only thing we need to live; we also need the energy to keep our cells and organs functioning.

Food was sparse for most of our species' history. With famine, a constant threat, being able to precisely forecast how much energy will be needed in the future was a tremendous evolutionary advantage.

The body, on the other hand, cannot store energy indefinitely. Attempting to do so would result in us becoming so obese that we would be unable to move - a significant evolutionary disadvantage. So, what's the best way to split the difference? So, just like the mechanism that regulates water intake and output, you construct a negative feedback system.

The main point is this: Overeating causes us to burn gasoline at a faster pace.

In 1976, Ethan Sims, an American scientist, conducted an experiment with volunteers recruited from a state jail in Burlington, Vermont.

Sims was fascinated by the subject of obesity. What would happen if people purposefully overate for three months to gain 25% of their body weight?

Sims increased the convicts' daily calorie intake from 2,200 to 4,000 calories, which is about double the amount required for an adult male. They soon acquired weight, as planned. But then something unusual occurred. Despite their high-calorie diet, their weight remained stable. Sims' daily rations were doubled to 10,000 calories. Surprisingly, many of the subjects failed to gain any additional weight. What exactly was going on?

Sims discovered the answer by measuring the inmates' metabolic rate, or how quickly their bodies burned energy. He discovered that each volunteer's metabolism had increased, indicating that they were burning calories at a higher rate than typical. They weren't an outlier, according to further study. Researchers at the Mayo Clinic in Rochester, Minnesota, examined 21 overfeeding tests in 2006 and found that overfeeding increases metabolic rate by 10% on average.

This research implies that, similar to how our kidneys release excess water to prevent overhydration, our systems strive to protect us from gaining too much weight. But, if we discover another negative feedback system, shouldn't it also self-correct in the opposite direction, protecting us against weight loss? And, if that's the case, why do so many diets fail? Let's see what we can find out!

6. Calorie limitation causes a decrease in metabolic rate.

The first metabolic rule is represented by an equation: energy in minus energy out = energy stored. Let's rewrite the regulation to make it a bit more concrete.

Food provides energy to the body, which it converts into heat, movement, and thought. As a result of these activities, energy is expended. If you consume more calories than you expend, the excess energy is stored in fat cells.

Weight loss should be simple if you follow this equation: all you have to do is burn more energy than you intake. That is, in fact, the counsel of almost every diet out there.

It's not that easy in reality. Dieters frequently plateau after initial weight loss success. They frequently acquire weight later on. To understand why we must examine the physiology of starvation.

The main point is that calorie restriction lowers metabolic rate.

Ancel Keys, a young nutritional scientist at Minnesota University, started a study in 1944 to see what happens to people's metabolism when they are starved.

For 12 weeks, volunteers were allowed to eat a diet that was appropriate for their occupation as manual workers. They consumed 3,200 calories per day during this time. After three months, Keys' calorie intake was decreased to just 1,500 per day, which he described as "semi-starvation."

The metabolic rates of the subjects had decreased after another three months. That wasn't unexpected. Weight loss usually leads to a slower metabolism because larger people have higher metabolisms than smaller people. Keys, on the other hand, had expected a 25% drop, not the enormous 50% drop he was seeing now. He also discovered that the volunteers' heartbeats were sluggish and that they were breathing more slowly when he examined them. Their body temperatures had dropped as well. Their bodies were, in a nutshell, shutting down. That was unexpected.

It had long-term consequences as well. When the subjects resumed their regular diets, their weight began to rise alarmingly quickly, which Keys attributed to their slowed metabolisms. Every subject finished the experiment heavier than when he began, and fat deposits mostly restored decreased muscular mass.

Limiting calorie intake is similar to reducing water intake in that it causes negative feedback. When faced with a lack of food, the body seeks to conserve energy by slowing down its metabolic rate. We can see why diets don't work today. Because the body can't distinguish if calorie restriction is voluntary or due to starvation, it takes a precautionary approach and activates the energy-saving switch to increase its chances of survival.

7. Our weight is controlled by hormonal signals.

The body has no way of knowing if we're dieting deliberately or not. Calorie limitation appears to be a famine and a threat to our survival. That is why it lowers its metabolic rate to save energy.

When the calorie restriction period is finished, our metabolism does not return to its prior state. We continue to burn fuel more slowly and store energy in fat cells, which serves as the body's safety net in case of hunger. All of this explains why diets fail. Starvation causes our biology to resist.

However, it also works to keep us from acquiring too much weight. Overfeeding raises the metabolic rate, as we've observed. What is the mechanism behind this negative feedback system? It's time to examine our fat cells more closely.

The main point here is that hormonal messengers are in charge of our weight.

Jeffrey Friedman, an American molecular geneticist, discovered the hormone leptin in 1994. His discovery allowed scientists to explain how the negative metabolic feedback mechanism works.

Remember how the kidney communicates with the help of a hormone called renin? Fat cells, on the other hand, communicate with the hypothalamus, the brain's weight-control centre, via leptin. Leptin tells the body how much energy it has stored. This information is then used by the brain to control two switches. The first turns on or off hunger, while the second increases or decreases metabolism.

Leptin is released into the bloodstream when we overeat and store extra energy in fat cells. The hypothalamus receives this communication and recognizes that the body has sufficient energy, thereby activating both switches. Appetite decreases and metabolism accelerates, limiting energy intake and depleting current energy stores more quickly, reducing weight gain.

Weight loss is also hampered by leptin. The number of fat cells in our body lowers when we restrict food, lowering the quantity of leptin in our blood. This signals the hypothalamus to stimulate appetite and slow metabolism. When these switches are triggered, weight loss is slowed and weight gain is quick once the food is freely available again.

All of this shows that our bodies are supposed to keep us in shape. Similarly to how the hydration system prevents us from drinking too much water, this metabolic system should keep us from eating too much food. Of course, this isn't the case; obesity is a global health crisis, particularly in the Western world. What is the reason for this? We'll try to explain this perplexing behaviour in the final concept.

8. Obesity is a given in today's Western diet environment.

Our forefathers and mothers were hunter-gatherers. The majority of their diet consisted of meat and starchy tubers like yams and sweet potatoes. Fatty offal like liver and bone marrow were desired. Their meals were rounded out with natural vegetables, fruits, seeds, nuts, and herbs.

Although our bodies resemble those of early Homo sapiens, the energy we utilize to power them is vastly different. Take, for example, a 2016 poll of nearly 9,000 Americans' eating habits.

Highly processed foods accounted for over 60% of their daily calorie consumption. Data from other Western countries support this conclusion. We consume far less natural fat and far more sugar and industrially generated vegetable oils than humans have ever consumed in the history of our species.

This is destroying the negative metabolic feedback loop, which is supposed to keep us from getting fat.

The main point is that today's Western eating environment is a recipe for obesity.

Heart disease was on the rise in the 1970s. Faced with an impending public health disaster, governments turned to science for solutions. However, the scientists they consulted were not objective truth-tellers; in reality, several significant studies were supported by industry lobbyists.

The sugar industry was the most powerful lobbyist of all. Fats, particularly saturated fats found in red meat, dairy, and butter, were blamed for the health catastrophe in research funded by "big sugar." The health risks of sugar consumption, which has been steadily increasing for over a century, were not investigated.

Governments initiated an effort against these fats in the 1980s. That choice is partly to blame for today's obesity pandemic. This is why.

Since governments began advising us to avoid saturated fats, our intake of vegetable oils such as sunflower, canola, and soybean oils has tripled. Omega-6 fat, a form of polyunsaturated fat found in nuts and seeds, is abundant in these processed oils. Omega-6 has two functions. To begin with, it stabilizes lipids, making them less susceptible to deterioration. This is beneficial to producers. Second, it reduces the efficiency of leptin, the fat cell hormone that keeps us slim. That is harmful to our health.

Manufacturers faced a predicament as a result of government directives to minimize saturated fats in food. How can you produce addictively delicious baked goods if you can't use butter? You use a lot of sugar, to be sure. The amount of sugar consumed by the general public has increased by 20 per cent since 1980. This has a negative impact on our blood sugar levels. We create too much insulin when they spike, which encourages cells to take more sugar from the blood. This causes our blood sugar levels to drop, making us need even more sweets - a tremendous urge to overeat.

Our bodies are biologically programmed to prevent fat. However, the modern food situation frequently overrides this programming.

The important message in this summary is that creatures evolved ways to produce more energy from food, which allowed life to flourish on Earth. Human evolution is a matter of energy as well. When we discovered a technical technique to unlock extra fuel in food: cooking, our brains became bigger and our bellies shrank. We also developed a negative feedback system to control our energy consumption. In times of plenty, our bodies' metabolic rates increase. They conserve energy by reducing our metabolism during times of famine. This should keep our weight in check, preventing us from being overweight or underweight, but our modern Western eating environment all too often overrides this biological system.