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Fat Is Important for Our Health but It Must Be the Right Kind

Written by Dr. Joseph Mercola Fact Checked

what fats should we eat or avoid

Story at-a-glance -

  • Humans store fat for evolutionary reasons that have helped us survive as a species
  • Instead of representing a lack of will power, obesity tends to result from the unique ways humans have evolved
  • Processed fats from cheap vegetable oils should be avoided to stay healthy yet 95 percent of restaurants use them in preparing food
  • Unlike marine-based omega-3 fats, processed omega-6 oils found in vegetable oils are damaging to the human body yet top medical organizations promote them
  • While once thought mostly inert, fat cells affect major body systems, from the brain and heart to sexual function and insulin resistance
  • Cheap, processed food containing partially hydrogenated vegetable oils is responsible for much of the damaging oils that are found in people's bodies today

Most people realize Flemish artist Peter Paul Rubens was one of the most influential artists of baroque tradition. Yet when they look at his paintings of unclothed women they are likely to see "fat." Fat bodies have become so associated with lack of health and lack of self-control that the myths have become separated from the truth. Let's make an effort to separate them.

First, dietary fat serves many important functions and is good for the body when the right fat is consumed. Secondly, having excessive adipose tissue — body fat — does not denote that a person lacks self-control or will power, but is the result of an inappropriate diet. Homo sapiens evolved with a "famine reflex" that caused metabolic changes to conserve fat and ensured survival when food was scarce.

The women depicted in Rubens' paintings were probably fairly healthy because they lived before the damaging fats of today had come into existence. They lived before industrial vegetable oils and seed oils became the norm in most processed food, and before our intake of processed omega-6 linoleic acid doubled or tripled, while our intake of omega-3s from plants and marine animals fell tenfold.

Luckily, we can eat in a way to avoid these damaging trends. The key is to reduce your omega-6 intake and to consume undamaged, unprocessed omega-6 in the form of plant seeds and tree nuts, not vegetable oils, while simultaneously increasing your omega-3 intake, especially marine-based omega-3. As a general recommendation, aim for 3 to 4 grams of omega-3 EPA and DHA, and 1 to 2 grams of whole food-based omega-6 linoleic acid per day.

Humans Have Evolution to Thank for Their Tendency to Store Fat

Humans have greater fat stores than most other mammals and there are several reasons for this, say evolutionary experts in a film done for Slate.1 First, early man had to find shelter and colonize in hostile environments such as caves that were cold and areas beset with predators.

Secondly, unlike other mammals whose offspring reach maturity quickly, human children have very long childhoods. A human child is essentially helpless for many years.

Evolutionary experts think the ability for women to store fat stems from their likely need to care for and nurse several helpless children at once, even when food sources were scarce. A woman living in prehistoric times might well have had a newborn baby, a 2-year-old, a 4-year-old and other young children with no assurance that food would be forthcoming anytime soon.

The Famine Reflex Also Explains the Tendency to Store Fat

Many thin or normal weight people are judgmental about the plight of their more rotund peers. “Why don't they just lose weight?” they ask. But the truth is, it is no easier for a fat person to lose weight than a thin person.

The famine reflex, also called the starvation response, is a set of adaptive biochemical and physiological changes that reduce human and other animals' metabolism in response to a lack of food.

Ordinarily, during short periods of a food shortage, to provide the brain the glucose it requires, humans will burn free fatty acids from their body fat stores and even small amounts of muscle tissue.

However, after long periods of food shortages and starvation, this changes. After we begin losing weight, our body will revert to our ancestral fast-and-famine need to conserve energy and our metabolism will slow to accommodate for the reduction in calories.2 While this may have protected our ancestors, it can make losing weight difficult and even impossible for some people. This is how Livestrong describes the phenomenon:3

“Your body is equipped with its own starvation defense mechanism, which has evolved over millions of years to protect you during times when food was scarce — a problem most people don't have today.

When you take in too few calories to support activity and normal physiological functioning, your body adapts by reducing the amount of energy it uses to accomplish tasks. Your body may also turn to lean muscle mass for energy in order to conserve its valuable fat stores, just in case it doesn't receive more food anytime soon.”

There Was No Diabetes in Hunter-Gatherer Days

The reason that hunter-gatherers did not become fat or develop diabetes is obvious. Until the agricultural and industrial revolutions, it was a rarity to obtain enough food to develop these conditions.

According to our evolutionary experts, if hunter-gatherers would have had access to abundant food sources as we do today, or labor saving devices, they would have acted exactly like us — and developed the same problems.4 Human biology has not changed; what has changed is our circumstances, and not for the better.

The Debut of Damaging Fats

The debut of damaging dietary fats can be traced to the invention of the cotton gin in the late 1700s in the United States. While the production of cotton greatly increased thanks to the gin, so did the production of cottonseeds, only a small percentage of which were needed to plant new crops.5

Flash-forward to the early 1900s when a German chemist discovered if a catalyst and heat were added to a vegetable oil and the hydrogen was removed, the liquid was converted to a solid. This process was called partial hydrogenation, and its effect on modern eating habits has been huge.

The immediate commercialization of partial hydrogenation was by Procter & Gamble with the creation of Crisco in 1911. Soon, through aggressive marketing, often in defiance of actual benefits of the product, Crisco became a first choice in American homes for cooking and baking.

Sixty million pounds of Crisco were sold soon after the product debuted, and Procter & Gamble gained medical respectability by donating $1.75 million to the American Heart Association (AHA), today the leading cardiovascular group.

To this day, the AHA and the dietary guidelines for Americans recommend we consume at least 5 to 10 percent of our calories as processed omega-6 fats which, as I have often written, are among the most harmful when consumed in excess.

Partially Hydrogenated Vegetable Oils Were an Unlikely Success Story

To understand the success of Crisco and the partially hydrogenated vegetable oils to follow (soy, canola, corn, peanut) you have to remember the particularities of the war years. First, refrigeration was not yet widespread and many households still had iceboxes, not refrigerators, making the nonperishable Crisco handy.

Secondly, households had been using lard — animal fat — for cooking and baking and lard was earmarked during the war years for the military and heavily rationed to American families. Finally, Crisco was considerably cheaper.

But producing such oils, many of which were originally industrial oils, was anything but natural. Multimillion-dollar machinery was and is required to get the oil out of the seed, and the seed has to be deodorized because it’s so toxic. When the product reaches human consumers, it is highly oxidized and damaging.

Why Are Heated Vegetable Oils Damaging?

Heated vegetable oils create harmful oxidation byproducts, especially when heated to high temperatures. More than 100 dangerous oxidation products have been found in a single piece of chicken fried in vegetable oils, says Nina Teicholz, author of “The Big Fat Surprise: Why Butter, Meat, and Cheese Belong in a Healthy Diet.”

Among the most harmful of these oxidation products are aldehydes, which are highly inflammatory and may promote heart disease and Alzheimer’s disease. As early as the 1940s, says Teicholz, a number of experiments conducted on animals revealed concerning results. Animals eating heated vegetable oils not only developed cirrhosis of the liver and enlarged livers, but they would also die prematurely.

What Fats Should We Eat or Avoid?

While omega-3 fats are crucial for brain and heart health, fighting inflammation, decreasing liver fat and overall obesity, and possessing many other positive actions, the damaged omega-6 fats found in processed industrial vegetable oils may do more harm than good. You do need omega-6, but as mentioned earlier, it should be in the form of whole foods (seeds and tree nuts), not vegetable oils.

Bottles of vegetable oil on shelves have been exposed to light 24/7, which oxidizes them, and when you cook with it, the oil oxidizes even further. Moreover, the natural vitamins and minerals and antioxidants found in the coatings of whole seeds and nuts, which protect them from oxidizing in your body, are absent.

When you consume these isolated oils, even if it’s a cold-pressed omega-6, the acid in your stomach will still oxidize it and create unwanted lipid hydro peroxides and aldehydes. These components encourage inflammation and other damage in your body.

Between 1959 and 2008, the linoleic acid concentration in subcutaneous adipose tissue in Americans increased by about 136 percent,6 from 9.1 percent to 21.5 percent.

Since the half-life of linoleic acid is about two years in adipose tissue, this is a reliable marker of intake, and this rise in linoleic acid intake parallels the increase in prevalence of both obesity and diabetes, suggesting the advice to eat more vegetable oils is an unwise one.

Omega-3 Fats Make You a More Efficient Fat Burner

According to James Nicolantonio, Pharm.D, author of “The Salt Fix” and coauthor of my latest book, “Superfuel,” omega-3 fats upregulategenes that activate beta-oxidation in your liver, which means it improves your ability to burn fat. Omega-6 fats, on the other hand, are primarily used for energy. Taken from a transcript of a recent interview I did with him, he explains:7

"Your basal metabolic rate goes up, because the cell membrane is so fluid. Your ability to get amino acids and glucose in and out of the cell are better. Your inflammation goes down, so you become a better fat-burning machine.

Actually, omega-3s help synthesize protein better too. Muscle protein synthesis dramatically goes up when you consume 3 to 4 grams of omega-3s, because amino acids, again, are flying in and out of the cell way faster when they’re saturated with DHA.

Studies have shown in middle-aged adults, as well as in the elderly, consuming 3 grams of DHA increases muscle strength, increases your maximum amount that you’re able to rep. Your grip strength is improved.

This is an important fat to help prevent sarcopenia. This is a very big issue, where elderly people are not even able to carry a milk carton throughout the grocery store. Really, the omega-3s are what’s going to hopefully help prevent a lot of the sarcopenia that’s happening or muscle lost during aging."

Why Is Linoleic Acid Damaging?

Before the omega-6 linoleic acid is even oxidized it damages the endothelium — the tissue that lines various organs and cavities of your body — as well as blood vessels and lymphatic vessels. It also causes an increase in penetration of low-density lipoprotein (LDL) and very low density lipoprotein (VLDL).

Once linoleic acid is oxidized it becomes even more harmful. It produces advanced lipoxidation end-products such as aldehydes that can actually crosslink proteins and create neurofibrillary tangles that are present in cases of Alzheimer’s disease. This, in my opinion, is contributing to the epidemic of neurodegenerative diseases we are now seeing.

Fat Performs Important Actions in Your Body

Fat was once thought to have few if any functions in the human body. Now, fat cells are recognized as affecting major organs in the body from the brain and heart to major systems like those governing sexual function and blood sugar/insulin resistance.

One example of how fat signals the reproductive and sexual systems is seen in women of childbearing age and their weight. It is well documented that when young women lose too much weight through dieting, anorexia or excessive exercise, their menstrual periods cease. The periods resume when sufficient fat stores are gained.

We now know that cells must be saturated with omega-3s-related DHA, a fatty acid found in the meat of cold-water fish, to exert antiplatelet effects. The fatty acid also lowers triglycerides and creates a more buoyant LDL.

The Ketogenic and Paleolithic Diets Often Need To Be Enhanced With Specifics on Fats

Many people just summarize the ketogenic and Paleolithic diets as being simply high-fat. While that is accurate to a point, it’s really not the full picture. If you choose the wrong fats, you’re actually going to run into more problems as we have seen in this article.

In fact, damaged fats are so deleterious to the human body, there is less danger in eating processed carbohydrates. That is something to think about the next time you’re confronted with a food product made with processed vegetable oils.

As noted by DiNicolantonio in a 2016 editorial in BMJ Openheart,8 the importance of balancing your omega-6 to omega-3 ratio for the prevention and management of obesity cannot be underestimated:

“[C]alories from vegetable oils high in linoleic acid … an omega-6 fatty acid, are proinflammatory and thrombogenic, whereas calories from eating fish high in omega-3 fatty acids are anti-inflammatory and antithrombotic …

The typical Western diet now provides an omega-6 to omega-3 ratio of around 16-to-1. High dietary intake of omega-6 fatty acids as occurs today leads to increases in white adipose tissue and chronic inflammation, which are the ‘hallmarks of obesity.’

Omega-6 and omega-3 fatty acids specifically metabolize to prostaglandins, thromboxane and leukotrienes. Prostaglandin E2 from arachidonic acid leads to differentiation and proliferation of adipose tissue and prostaglandin F2α, also from arachidonic acid, prevents the browning of white adipose tissue, which is the good fat tissue as it increases thermogenesis, burning fat through the release of heat.”

DiNicolantonio also notes that by acting directly on your central nervous system, omega-3 and omega-6 fatty acids influence your food intake and your body’s sensitivity to insulin and leptin — but again in opposite directions.

While omega-6 has been shown to increase insulin and leptin resistance, diabetes and obesity in both rodent and human models, omega-3 has the converse effect, and can help “reverse the dysregulation of this system, improve insulin sensitivity and control body fat,” DiNicolantonio writes, adding “It is therefore essential to return to a balanced dietary omega-6 to omega-3 ratio based on data from evolutionary studies.”