Does Nature Want Us to Be Fat?

If you are obese, you increase food intake triggered by hunger, cravings, loss of control, and foraging behavior. You may not realize it, but you also have reduced metabolism when at rest. All of this leads to fat accumulation. 

Book Review: Nature Wants Us to Be Fat, by Richard J. Johnson, MD

Dr. Johnson is a professor of medicine at the University of Colorado and is a clinician, educator, and researcher. He researched the cause of obesity.

The foundation of this book is based on the concept that our genetic makeup was designed to maximize survival in times of food insecurity, that our genes continue to maximize survival even in times of food abundance, and that fructose is the primary trigger for obesity. He uses nature and science to explain the process. 

Nature wants us to have sufficient fat to survive when situations are rough. 

Consider animals. For example, the emperor penguin, who can be four feet tall and weigh 40-50 lbs., nests during the winter. One to two months before nesting they start gaining weight, nearly doubling in size. The mother lays a single egg, and the father sits on the egg for two months, fasting. The accumulated fat protects him until the mother returns, and he can find food to regain his weight. 

They prepare for this a month or two before the food shortage. Animals’ behavior changes. They become excessively hungry and forage intently for food. They eat much more than usual and become insulin resistant. 

Other animals that hibernate, such as the black bear and grizzly bear, increase their food intake in the fall to build up fat in preparation for the winter. They conserve energy by slowing their metabolism. By eating more while using less energy, the food is turned into fat. During hibernation, their body temperature drops to near freezing to slow their heart rate and metabolism even more. Their fat stores provide necessary water. Hibernation lasts as long as they have fat to burn. Once fat supplies become low, the animal starts breaking down the protein in its muscle for energy. This triggers an alarm. The animal will wake from sleep or abandon its egg, to attempt to refuel.

The biological process that animals use to help them survive, i.e. to put on fat, when food is scarce, is what Dr. Johnson calls the survival switch. 

The problem is that humans today have this survival switch and keep it persistently on. We are continually preparing for hibernation. This is now a fat switch which drives obesity. We are constantly preparing for a winter that never comes. We now live in an environment that is a mismatch for our genetic makeup.

Why are we gaining weight? 

1. The abundance of food. 
2. Transportation resulting in our exercising less and sitting more.
3. The introduction of fast food, processed food, and junk food. 
4. The increase in food portion size. 
5. Biology – we don’t have a sensation of satiety. 

1. Normally, we should feel satiated after a meal because a hormone called leptin tells a region in the brain called the hypothalamus to signal us to stop eating. However, people who are overweight respond poorly to the leptin signal (leptin resistance) and so remain hungry longer. 
2. People who are overweight don’t burn fat as well as those without excess fat. 

Let’s go back to animals that hibernate. What triggers their period of increased eating, followed by the cessation of eating and the beginning of hibernating? 

1. A drop in temperature?
2. Changes in the length of day and night?
3. Triggered once the animal accumulates a certain level of fat? 
4. Is it the unavailability of food and sometimes water?  (Most studies suggest this.)
5. Dr. Johnson believes that, at least in some animals, the survival program is initiated by eating a specific food with unique properties. Fructose (fruit sugar). 

Fructose is a major component of table sugar (sucrose) and is also in the sweetener, high fructose corn syrup. Fructose triggers weight gain for animals in the wild. Think of bears and fruit or honey. 

The average American adult consumes about 17 teaspoons of added sugar per day, far exceeding recommended limits. We are out of control. The American Heart Association recommends limiting added sugar to 9 teaspoons (36 grams) per day for men and 6 teaspoons per day for women. High sugar intake is linked to various health problems, including obesity, type 2 diabetes, and heart disease.

Hibernating animals seek and consume substantial amounts of fructose to gain weight in preparation for hibernation. As a side note, bears do not eat fruit until late fall, when it ripens, increasing the fruit’s sugar content. One study found over 60,000 grape seeds in one sample of bear scat, which is consistent with the bear having eaten approximately 10,000 grapes during the prior 24-48 hours. It is not always the fittest that survives; it may be the fattest.

Observations of nature are important, but they have also completed scientific studies. Dr. Johnson started studying Fructose in 2004. 

He studied mice. Normally, if you give an animal a high-calorie drink, they will reduce the amount of food they eat so that their overall caloric intake remains the same. The mice were given fructose in their water, and they initially compensated by decreasing their food intake. However, after several weeks, this pattern changed. They continued to drink the fructose and increased their calories. They acted as if they were persistently hungry and became less active; therefore, their metabolism was decreased. After several months, they developed fatty-liver and insulin resistance. 

Fructose sugar signals the body to prepare for food scarcity and to make and store fat for a calorie reserve. The fat can be broken down to provide energy if no food is available.

This is the biological “switch” that was turned on by fructose. In a 2006 paper published in the American Journal of Physiology, Dr. Johnson’s research group demonstrated that this fructose-induced switch is not driven from the calories in fructose, but rather because fructose causes a depletion of energy in the cell. This energy depletion activates an alarm that triggers the metabolic response to gain fat and become insulin resistant.

He says, “Indeed, the biological switch also stimulates hunger and thirst, foraging behavior, loss of control of appetite, and reducing oxygen needs while increasing inflammation. It is really an orchestrated event that was activated by one particular food—and that food was fructose.”

In essence, the way that fructose works is that it mimics starvation by creating a low-energy state within the cells, signaling to the body that there is an energy crisis.

“Fructose is what flips the switch to the ‘on’ position,” said Dr. Johnson.

Fructose triggers addictive-like behaviors. When we eat sweet foods, it triggers the release of dopamine in our brains that provides a sense of pleasure. That pleasure can lead to cravings, which resemble addiction. Mice who were provided sugar water intermittently drank it very fast when it was available and showed signs of anxiety and withdrawal when the sugar water was not available. 

Sucrose and HFCS (high fructose corn syrup) stimulate the same parts of the brain as does heroin. Alcoholism is a sugar disorder. Our love for sugars can turn into a true addiction. 

When the survival switch is triggered by fructose, it leads to:

Hunger	Driven by low ATP levels, which simulates starvation, and by leptin resistance, which prevents us from recognizing when we are full.
Craving	Driven by fructose metabolism in the intestines and possibly the brain.
Foraging behavior	Aids in the search for food in unfamiliar areas. Includes risk taking, impulsiveness, rapid decision-making, and aggression.
Increased food intake	Driven by hunger, craving, and foraging
Reduced metabolism when at rest	Allows the body to conserve energy when not needed for foraging.
Fat accumulation

 

Dr. Johnson also addresses the need to avoid high-glycemic carbs such as white bread, white rice, potatoes, chips, cereals, and crackers. High glycemic carbohydrates are foods that quickly raise blood sugar levels. This means they are rapidly digested and absorbed, leading to a swift increase in glucose in the bloodstream.

Salt is a contributor to obesity. After 5-6 months, mice on a high salt diet had become extraordinarily fat compared to mice on a normal-salt diet. 

To be healthy, you should drink eight cups/glasses of water per day. Again, Dr. Johnson: “By doubling the animals’ water intake, we could block obesity and insulin resistance. And even if we waited to increase the animals’ water intake until after they were already fat, we could prevent further weight gain even if they continued on the high-sugar, high fat diet.” 

Dr. Johnson acknowledges that the consumption of fructose, excess salt, and dehydration are not the only contributors to obesity. But the fat switch is the major factor driving obesity. Other factors are socioeconomics, education, cultural mores, genetics, and bacteria in the gut. 

So, what does Dr. Johnson recommend to lose weight? 

“The ideal diet is one that does not restrict calories, but rather naturally reduces caloric intake by quelling hunger.” How do you quell hunger? You reduce sugar, HFCS, high-glycemic carbs, salt, and drink plenty of water. Diets that restrict sugar and carbs can cause weight loss even without specifically restricting calories. When you reduce hunger, caloric restriction occurs naturally.

Dr. Johnson also suggests that intermittent fasting may reset the system. And he recommends increasing energy consumption by exercising for at least an hour, 3-4x/wk. 

Specifically, Dr. Johnson prefers a low-carb, keto, or Mediterranean Diet, with intermittent fasting 1-2 days per week. Minimize or avoid alcohol. Add a daily vitamin C supplement of 500 mg or less.

However, losing weight is not the problem because most diets can achieve this. Regaining weight is. We rarely sustain our weight loss. 

1. The primary biological problem is that when you have been overweight for a while, your body begins to think of your current weight as normal. Your body wants to return to its higher weight.
2. Eating the same plate of food that kept you in balance before you started to lose weight now causes weight gain. You must eat less than you used to or you will regain the weight. 

For some people, “maintaining their diet and exercise plans continues to require constant vigilance and immense emotional and mental drive.” We need to abandon a diet mindset and develop a lifestyle of healthy eating.