Does Nature Want Us To Be Fat?


“Nature Wants Us to Be Fat” is the name of the new book by Richard Johnson, MD. This provocative book explores new science on why we gain weight and what to do about it.

If you already think you know everything there is to know about the obesity crisis, you are in for a few curve-ball surprises!

We will take a deep dive into Dr. Johnson’s major findings and how you can use them to tackle your weight issue and improve your health.

The history of our many theories about weight gain and the obesity crisis is fascinating. And getting the answer right is pivotal.

As Toronto Kidney Specialist and fasting guru, Dr. Jason Fung has said, ‘why we get fat is the most important question to answer’ because:

“If you get that question wrong, everything you do after that is wrong. Everything. All your treatments are wrong, all your drugs are wrong, the way you think about obesity is all wrong.” (1)

Today, sugar’s role in weight gain is well documented. But this understanding of sugar’s ill effect on human health – including weight gain – is not new. 

In fact, check out this article that appeared in the New York Times on May, 22, 1857: 

“We are, beyond question, the greatest sugar-consumers in the world, and many of our diseases may be attributed to the too free use of sweet food.” —New York Times, May 22, 1857 (2)

If the author of that article thought Americans ate too much sugar in 1857, he would be gob-smacked by our current rate of consumption and our matching rates of disease and obesity. 

A few years later across the Atlantic Ocean, William Banting, a British mortician, lost 60 pounds on what would now be called a low carbohydrate diet. His 50-page pamphlet “Letter on Corpulence”, published in 1864, is considered the first widely distributed weight loss book. It is still in print today.

The items from which I was advised to abstain as much as possible were — Bread, butter, milk, sugar, beer, and potatoes, which had been the main (and, I thought, innocent) elements of my existence... These, said my excellent adviser, contain starch and saccharine matter, tending to create fat, and should be avoided altogether. (3)

Since 1864 our consumption of quickie carbs and processed food products has exploded. Food makers realized sugar in particular served many useful purposes. It improved the texture of baked goods, served well as a preservative and of course, it makes things taste sweet and sweet foods fly off the shelves.

Starting in the 1950s, despite a Century of belief that it was carbohydrates, and especially simple, high glycemic carbs that made us get fat, influential researcher Ancel Keys published an article blaming saturated fat for the increase in heart disease after World War II in his famous Seven Countries Study. (4) 

This research facilitated a widespread food culture shift that placed an emphasis on the importance of low-fat foods while minimizing or ignoring the health risk of added sugars. This allowed new and more concentrated forms of sugar to enter the food chain with little to no resistance including both the introduction of high fructose corn syrup in the 1970’s and the artificial sweetener Aspartame. 

Interestingly, Keys did not promote or eat a low-fat diet himself. (5) In fact, his 1975 book “Eat Well and Stay Well the Mediterranean Way” advocated a balanced whole food diet. Whatever can be said of Keys Heart Health Study, how he ate worked for him, he died a few months short of his 101st birthday.

The Keys-inspired low-fat dietary revolution took a hit when New York City Cardiologist, Dr. Robert Atkins brought our attention back to sugar’s role in weight gain and health issues. Dr. Atkins believed quickie carbs – not fat – were responsible for heart disease and weight gain. 

In 2010 Gary Taubes wrote, “Why We Get Fat” which implicated insulin in particular as the cause of obesity. Dr. Jason Fung elaborated on this concept in his 2016 book, “The Obesity Code”. 

Now in 2022, Dr. Richard Johnson, MD has written “Why Nature Wants Us to Be Fat” which scientifically adds to the conversation by pointing the finger at fructose as the main driver of obesity and related chronic disease.

Dr. Johnson’s previous book published in 2008, “The Sugar Fix: The High-Fructose Fallout That Is Making You Fat and Sick”, argues that concentrated sweet foods signal our body to conserve energy and store fat. When food was hard to find and the risk of starvation was real, survival of the fittest became survival of the fattest. Thus, our ancestors became very good at storing fat. This was a good thing!

However, today we have access to as much food as we want and 60-70% of it is loaded with added sugar and high fructose corn syrup. Under these circumstances, our ability to make and store fat is no longer a survival advantage, it is life-threatening.

Why does fructose lead to weight gain and obesity? 

Dr. Johnson’s research shows it activates a “Survival Switch”, which is a series of intricate biological processes that help us store fat and reduce energy expenditure. The constant activation of this switch results in obesity and a myriad of other chronic modern diseases such as Alzheimer’s, diabetes, heart disease, stroke, and cancer.

His thesis is fructose activates a “Survival Switch”, which is a series of biological processes that compels the body to eat more, lower its metabolism and gain fat.

Evolutionarily this was extremely valuable in times when food was scarce. But constant activation of this switch results in obesity and other chronic modern diseases such as Alzheimer’s, diabetes, heart disease, stroke, and cancer.

Dr. Johnson makes the case that fructose (6) in particular is a sugar that drives the obesity epidemic and its rising rates.

This may sound like hype, but it is not. 

Before delving into specifics, we need to make one caveat: most of Dr. Johnson’s research is on mice since human studies are extremely difficult to do. Too many variables and too little control over human behaviours. 

Fortunately, and surprisingly, metabolic processes are comparable between mice and mankind. And in particular, the metabolism of fructose is remarkably similar. Thus, research on mice is generally considered to be an important window of insight into human health.

In one fascinating study, mice were genetically modified to lack fructokinase, the enzyme that breaks down fructose which meant it was not absorbed. These mice did not prefer fructose-sweetened water over plain water, as regular mice did, and these mice did not gain weight and stayed lean to a very old age. (7)

Fructose, Dr. Johnson's science suggests, appears to lend itself to weight gain and obesity in 3 ways:

  1. It triggers the Fat Switch or Survival Switch
  2. It dampens satiation hormones and compels overeating and binge eating 
  3. It ramps down our metabolic baseline, we burn fewer calories and produce less energy

In short, fructose tells the body to eat, store fructose as fat, and slow down its metabolism including creating an aversion to exercise.

It does all this for wonderful life-preserving reasons. This triple whammy protects us in times of food scarcity (droughts, long winters), long flights (think migrating birds) and freezing temperatures (think hibernation).  

One would think, awesome, I will simply stop eating foods with fructose (free fructose in particular the kind found in processed foods, fruit juice, sugar drinks, etc.), that will solve my weight gain or obesity problem.

Unfortunately, it is not that simple. 

Because as some of you know... some people who cut out or don't eat much sugar/fructose can still gain weight and develop metabolic syndrome. 

How is this possible?!

Enter the polyol pathway…

The polyol pathway is a complex process that facilitates the conversion of excess glucose (blood sugar) to fructose. This pathway was felt to be minimally active in most people and thus inconsequential. 

Dr. Johnson found that mice given high doses of glucose ended up obese with fatty liver disease. No surprise there. But! What he also found was the presence of fructose in their liver even though there was no fructose in their diet. Where did it come from?

Dr. Johnson proposes the polyol pathway was turned on and manufacturing fructose. 

OMG! Our bodies can make fructose from glucose? (I thought it was shocking enough that our bodies can manufacture alcohol in quantities high enough to not legally drive a vehicle.) 

Dr. Johnson's experiment was repeated with mice who could not metabolize/absorb fructose. Those mice did gain weight, but they did not get obese, nor did they develop fatty liver or insulin resistance. In his words:

“It was a major breakthrough, simultaneously exhilarating and depressing. It is not just the fructose we eat that causes obesity; it is the fructose we make. 

Dr. Johnson continues:

What is more, glucose, a major component of the carbohydrates in our diet, could be converted to fructose in our body. Yes, there was a little evidence that glucose itself could cause some obesity… however, much of the weight gain, and almost all of the insulin resistance and fatty liver, that follows high intake of glucose appears due to the fructose that the body makes from that glucose.”(8)

The polyol pathway is activated when glucose levels rise quickly and intensely. 

This means high glycemic foods are far more likely to be converted to fructose than foods whose carbohydrates are broken down slower. This is why soft drinks are especially problematic. Not only do they contain free fructose but the glucose (9) is digested quickly and activates the polyol pathway.

Thus, for obvious reasons, if you want to avoid or reverse obesity, you need to avoid high blood sugar by eating low or lower carbohydrate diets. This is possible to do on Vegan, Vegetarian, Paleo, Keto, and Carnivore meal plans, any whole food meal plan actually. Just limit grains, high-sugar fruits, and high-carb veggies. That leaves hundreds of other lower-carb nutrient-dense food choices to enjoy.

But wait there’s more!

Dr. Johnson found that it is not just fructose itself and high glycemic foods (sugars and flour) that turn on the fat storage survival switch. 

There are two more situations that trigger the body to manufacture fructose (without consuming fructose or glucose) leading to fat storage, urges to overeat, and a reduction in energy expenditure and production.

I suspect one of them you will find as shocking as I did.

Stay tuned…!




(2) As quoted by Gary Taubes’ book “The Case Against Sugar” (2017)




(6) Fructose is known as fruit sugar and is found in fruit. It is also a component of table sugar or sucrose. Sucrose is made up of 50% glucose (blood sugar) and 50% fructose.

(7) Pages 54 – 56 Nature Wants Us to Be Fat by Richard Johnson MD, Benbella Books, February 2022.

(8) Page 86 Nature Wants Us to Be Fat

(9) The sugar in soft drinks is usually sucrose which is 50% fructose unless of course High Fructose Corn Syrup is used which is typically 55% fructose.

1 comment

Priscilla Leach

Hello Ms. Christophers, 

I want to compliment you on this excellent article summarizing Dr. Richard Johnson's book "Nature Wants Us to be Fat."  I am reading his book now and was looking for a summary to share with my adult kids and friends that wouldn't scare them off with the biochemical/technical deep dive he provides.  I am grateful for his book, but I know many others would be too impatient to read it.  (Just tell me what to eat! Right?) My dad was a hearing research scientist, so I can appreciate the creativity and time such research takes.  And it takes someone like you to translate it into approachable content to help others understand that this obesity epidemic is not due to our moral failings.  It was so interesting learning about the history of the Sugar Trade, and its role in international economy and wars, too.

Thank you, 
Priscilla H. Leach

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