8 min read
What is the cause of obesity?
Recently, the world has seen an enormous epidemic of obesity. This drives most of our top chronic diseases, making it arguably the most significant health issue of our times.
Why did this happen? New science has finally determined the main cause. While many minor factors influence our weight, one single cause appears to be behind most of the problems.
If you are like most people, you could benefit from losing some excess body weight. Knowing the most effective way to do this can be extremely helpful.
This is not yet obvious when reading the media, which is happy chasing clicks with various new theories or studies. This results in them constantly publishing contradictory stories.
Unfortunately, the current situation is also worth trillions of dollars for the food and pharmaceutical industries. They have a duty to their shareholders to maintain this ultra-profitable status quo. One way to do that is to add uncertainty and doubt, through funding studies, experts, and lobbyists, keeping people confused and sick.
Furthermore, various researchers and influencers keep pushing their pet theories to further their careers and financial interests.
Despite the resistance and confusion, there is hope on the horizon. New science has appeared in recent years, showing a way to break free. Leaning on brilliant recent work from some of the world’s top scientists, we will share these insights for free here and provide simple tools to transform your health. The obesity epidemic seems to have been mostly caused by one thing, and it looks entirely possible to fix it.
Let’s start at the beginning, with a brief history of the disaster.
The epidemic
The obesity epidemic started slowly a few hundred years ago and then exploded over the past few decades. Here's data from the USA, which has led the way.
Obesity was still rare, perhaps only 1% of US adults, at the beginning of the 19th century. Previously, it had been virtually non-existent. Note that when examining hunter-gatherer tribes, humans living without access to modern foods, we find 0% obesity.
However, something new started happening during the 19th century. Obesity appears to have become increasingly common, reaching perhaps 4% of adults by the year 1900. During the first half of the 20th century, the epidemic spread even faster; by the end of the 1970s, it reached 15%. From the 1980s, things took off with rates exploding up to over 40% obesity by the 2020s.
Over the past two centuries, obesity has become 40 times more common! This is not just a curious and cosmetic issue. With obesity, the risks of all our top chronic diseases go way up. If we could find the cause and remove it, we could become healthier than ever. This is the number one health issue of our time.
What caused the epidemic?
There’s no shortage of attempted explanations for the obesity epidemic. There are literally hundreds of suggested causes, each championed by certain researchers or influencers. As mentioned, they often depend on this to further their careers or financial success.
However, all except one of these factors fail to explain the massive increase in obesity over the past two centuries. Meanwhile, that one promising explanation gets more and more scientific support.
Let’s quickly go through some of the most commonly discussed factors.
Genetics
It’s often claimed that obesity is “genetic,” and indeed studies show that there are hundreds of common genes that each have a slight influence on our body weight. With an “unlucky” distribution of these genes, some people are indeed far more likely to gain weight than others, this is true.
However, at a population level, it takes many thousands of years for a meaningful shift in our gene pool. Not much has happened to our average genes since the year 1800, and even less since the epidemic really sped up in the 1980s.
In other words, the obesity epidemic has virtually nothing to do with our genes. If we can remove the real cause of common obesity, the large majority of people would likely regain a normal weight, no matter their genes.
Willpower
If people just had more willpower, they would perhaps “put the fork down” and stop eating so much. Or they would move more.
Just like we can't blame genetic changes for the epidemic, it’s easy to see how wrong the "willpower" idea is. Obesity has increased in every age group, for both genders, in all countries, and the curves all move in the same direction at the same time. In the US, more than 75% of adults are now overweight.
Blaming willpower would require us to believe that people everywhere lost their willpower simultaneously and have never found a way to regain it over the past 200 years. This is an absurd idea; it's plainly wrong.
The reality is that just like breathing or drinking water, our food intake is regulated from our brain. We can only consciously control it for a brief time using willpower. In the long term – over years – our brain subconsciously control how much we breathe, drink and eat. We eat when we’re hungry, and we stop when we feel full.
Something in our environment disturbed this appetite control system to cause the obesity epidemic, and it has little or nothing to do with willpower.
Stress and sleep
A lack of sleep and long-time stress can make us eat more and gain weight. However, this effect seems to be relatively modest at a population level.
While it’s a great idea to get enough quality sleep, the best evidence we have indicates that sleep deprivation and stress can only explain a very small part of the obesity epidemic.
Mental health and childhood trauma
Some psychiatric drugs increase appetite and result in significant weight gain, and people who report childhood trauma are more likely to have weight problems later in life.
However, there’s no 200 years long epidemic of worsening mental health or childhood trauma. The latter may even be less common today than for previous generations.
It’s hard to see how this can have a significant impact on the overall obesity epidemic.
The microbiome
Can the bacteria that live in our gut influence our weight? Over the past decade, there has been much interest in this question. Certain gut bacteria are more common in lean people, while others are more common in obese people. This was an intriguing finding, worthy of testing.
However, there have now been seven (7) studies where gut bacteria from lean humans are "transplanted" to obese people. None of these studies has shown any positive effect on weight whatsoever. Getting the "lean" microbiome made no difference for people's weight.
A likely explanation is that changing what we eat changes *both* our weight and our gut microbiome. There does not appear to be any obvious benefit to manipulatíng the gut bacteria directly, at least not to lose weight.
Calories in, calories out
The laws of physics (thermodynamics) specify that energy can not disappear. In other words, any food calories absorbed into the body must be burned, or the person's body weight will increase.
Therefore, if someone has gained body weight, the person has taken in more calories than they have expended. However, this does not explain the real cause. It's just another way to state the question. The question is *why* do so many people take in more calories than they burn?
There are two basic explanations for the obesity epidemic. Either people eat more calories today, or they burn fewer calories. Let's start with the latter option.
Exercise
In the modern world, there is less need to be physically active. For example, with an office job, people can be less physically active than in many previous jobs, e.g., being a farmer. Cars and other transport options also reduce the need to move.
It seems reasonable that this leads to the average person burning fewer calories in the modern world, which could result in storing more body fat.
However, recently this theory has been repeatedly tested, with surprising results. It turns out that groups of people burn close to the same amount of calories even when physical activity is dramatically different. This has been seen with hunter-gatherers in Africa, farmers, etc., and compared to sedentary people in developed countries.
It turns out that long-term, over months and years, the body adapts to the level of physical activity. With more physical activity, the body spends fewer calories on things like anxiety, the immune system, and reproduction. We also tend to move less during the rest of the day after exercising.
This may help explain why exercise programs yield modest weight loss results—usually just 1-3 kilograms, far less than expected. Exercise is great for health and strength, but surprisingly ineffective for weight loss. The body compensates.
The bottom line is that since sedentary Western people burn almost as many calories as active hunter-gatherers, the obesity epidemic was not caused by a lack of "calories out." It's not about a lack of exercise. Instead, it must be about too many calories in.
Something must have made us eat far more.
The food environment
None of the many factors above gets even close to explaining the obesity epidemic. So what could explain why we suddenly eat far too many calories?
We have one major suspect left to explore. Clearly, our food environment has changed profoundly over the past 200 years. Perhaps these changes to our food are why we eat more today.
Over the past few years, three carefully controlled studies have shown that this (bingo!) is indeed the answer. It turns out that when people eat mostly modern ultra-processed foods, they eat at least 500 - 1,000 calories more per day!
This is an enormous increase, easily enough to explain the entire obesity epidemic.
Ultra-processed foods are becoming increasingly common, now accounting for more than half the foods eaten in many developed countries. These foods are highly profitable, and the more they make us eat, the more the food industry can sell. This means they are incentivized to create foods that make us eat more; arguably, they *have* to do this to stay competitive.
This problem, causing the obesity epidemic, is no coincidence. Ultra-processed foods make us eat far more by design.
The most obvious solution is to avoid all ultra-processed foods, but this is very hard to do in today's society and may not be entirely necessary. There are indications that some ultra-processed foods may be far worse than others, while a few could even be helpful for weight loss.
Importantly, we still need to figure out *why* the average ultra-processed food makes us eat far more than "real," old-fashioned, less processed foods. Many differences could explain the results.
Is it the refined sugar and carbs? The added fat? The lack of protein or other nutrients? The animal products? Is it due to certain additives? Or is it due to something else (how fast people eat these foods?), or a combination of many factors?
How do we explain this, and what is the best diet for you?
This is the million-dollar question, and scientists are beginning to figure it out. We now know more than ever, enough to make several helpful recommendations. This is the topic for another post, which is coming soon.
