We’ve swapped traditional fats for polyunsaturated fats (PUFAs), and now our biology, metabolism and waistlines are paying the price.
Just a few generations ago, dietary fats were higher in saturated fats. But over the last century, that all changed. Saturated fat rich butter, tallow and real dairy were pushed aside for unsaturated fat rich margarine, seed oils and plant-based dairy alternatives, thanks to misguided health advice, government subsidies and Big Ag’s bottom line - leaving us more inflamed, more overweight, more chronically ill, and more confused than ever.
Today, the ratio of saturated to unsaturated fats in our diets has completely flipped. We’ve drastically increased our intake of plant-based polyunsaturated fats (PUFAs) such as Linoleic Acid (LA) and Alpha-Linoleic Acid (ALA), while more traditional fats higher in saturated fats (SFA) have been demonized and largely phased out.
Saturated and unsaturated fats send different metabolic signals to your cells which impacts body weight regulation and cellular energy production.
In 1900, these plant-based PUFAs made up just 1–2% of daily caloric intake. Today, they account for 15% or more (r), a 5–6X increase that is driving metabolic dysfunction, inflammation, and chronic disease.
But this shift didn’t just change what’s on our plates -- it changed us, because dietary fat isn’t just fuel, it becomes part of our cells, impacts our hormones, and influences our metabolism. So when we change the fats we consume, we’re altering how our body functions.
We’ve radically altered the fatty acid composition of our diets—and in doing so, we’ve rewired our metabolic signaling, slowed our metabolic rates, ramped up fat-storing enzymes, and, simply put, we’ve gotten fatter.
But the change doesn’t stop with what we eat…it extends to what our livestock eat.
Their natural, species-appropriate diets have been replaced with PUFA rich feed ingredients, including corn, soy, flax, and industrial byproducts like dried distillers’ grains and vegetable oil residues. This shift has dramatically altered the fat composition of pork, chicken, turkey, and even eggs - making these foods higher in PUFAs than ever before. (r,r) Scientists and food producers have now shown that the fatty acid composition of milk and dairy can be manipulated simply by changing what cows and goats are fed. (r)
“Saturated FA levels in [chicken fat tissue] decreased significantly…with an increase in dietary PUFA…. The concentration of linoleic acid increased significantly with an increase in dietary PUFA.” (r)
In short: what livestock eat directly alters the fat profile of their meat - resulting in more PUFAs and less metabolism-supporting saturated fat in the food you consume.
So even if you’re not cooking with seed oils and are avoiding PUFA rich plant-based dairy alternatives, you’re likely still getting more of these metabolism-suppressing plant-based PUFAs, hidden in the fat of most modern meat, dairy, and eggs.
We’re not just changing what we eat. We’re changing the nutritional makeup of our entire food chain.
some animal fats now resemble canola oil
A higher PUFA diet for livestock means more PUFAs in the final product that we then consume. And due to this shift in how animals are fed, conventional pork, chicken, and eggs can now contain as much PUFA as canola oil. (r,r)
That means you’re not only eating more dietary PUFA, which suppresses your metabolic rate, but also more toxic oxidation byproducts that form when these unstable fats are exposed to heat during cooking.
PUFAs are highly unstable. When subjected to heat, light, or oxygen—as happens in most kitchens—they oxidize easily, producing harmful compounds. Research shows that meat and eggs with higher PUFA levels oxidize faster (r), which may increase inflammation, disrupt metabolism, and contribute to cellular damage in the body.
And how is this fat swap working for us?
A staggering 93% of Americans are not metabolically healthy and more than one-third of U.S. adults have prediabetes. (r) What's worse - the rates of obesity, cardiovascular disease, and Type 2 diabetes continue to climb and our life expectancy is declining. (r)
It’s a loud and clear signal - our metabolisms are not functioning the way they should.
We changed our dietary fats and it's negatively impacting our health.
Before diving into why PUFAs can cause health problems, let’s first clarify what a PUFA actually is.
Understanding Fatty Acids: The Structural Differences That Matter
Fats are a group of chemical compounds that contain fatty acids - the building blocks of the fat in our bodies and in the food we eat. At the molecular level, different types of fatty acids have different structural properties, which determine how they behave in the body:
- - Saturated Fats (SFA): Contain only single bonds between carbon atoms, making them highly stable and resistant to oxidation. Examples include stearic acid, palmitic acid, C15:0, and lauric acid.
- - Monounsaturated Fats (MUFA): Contain one double bond, making them slightly more reactive than SFAs but still relatively stable. Olive oil (high in oleic acid) is a well-known MUFA source. When consumed in high quantities, MUFAs increase the expression of 'fat making' enzymes.
- - Polyunsaturated Fats (PUFA): Contain multiple double bonds, making them highly prone to oxidation. This category includes both omega-6s like Linoleic Acid (LA) found in seed oils and omega-3s like plant-based ALA high in seed oils, nuts and flax and DHA and EPA, high in fish.
The double bonds in unsaturated fats (indicated by red arrows above) create “kinks” in their chemical structure, making them less stable than saturated fats and more prone to oxidation (r,r) -- losing electrons when exposed to heat, light, and oxygen. This instability not only increases cellular damage and inflammation but also alters signaling pathways and biological functions, ultimately impacting metabolism and overall health.
All dietary fat sources are a combination of these different types of fats, with their ratios varying depending on the source. For example, butter and cheese contain a much higher proportion of saturated fat and a more favorable saturated-to-unsaturated fat ratio compared to margarine, which is made from seed oils and loaded with PUFAs. While both may contain similar amounts of total fat per tablespoon, their composition and the ratio between saturated and unsaturated fats determines how they affect cellular health, metabolic signaling, and overall function in the body.
Different fats = different structures = different effects in the body.
We've seen a large increase in our plant-based PUFA consumption: LA and ALA, and a reduction in the consumption of health promoting SFAs like stearic acid and C15:0 which help stabilize blood sugar, boost metabolic health, and support sustainable fat loss. (r,r)
Foods high in plant-based PUFAs (like LA and ALA) include:
- - Vegetable (seed) oils
- - Nuts and seeds
- - Conventional pork & chicken product, and conventional eggs (even pasture-raised will contain higher levels if fed standard feed)
- - Many plant-based dairy alternatives (like soy, almond, oat)
Why does this matter? What are the consequences of this big fat shift? Let’s dive in.
The Health Consequences of The Big Fat Exchange
The modern diet’s heavy reliance on plant-based unsaturated fats, and the resulting imbalance between saturated and unsaturated fatty acids, has profound consequences for human health, including:
- - Slows metabolic rate
- - Lowers energy levels
- - Increases infertility rates
- - Disrupts hormonal balance
- - Promotes weight gain & increases obesity risk
- - Elevates stress levels
- - Increases cellular damage
- - Faster skin damage & aging
- - Impairs gut health
- - Weakens the immune systems
- - Impairs our ability to use carbohydrates
- - Alters the types of fat stored in your body
- - Changes the fat composition of breast milk
[If you’d like to dig deeper into the science and explore the studies behind these health effects, check out the full blog post here.]
The dramatic shift in the types of fats we consume isn’t just a small dietary change that simply drives inflammation, it’s a biological disruption that actively reshapes our physiology, acccelearates aging and disease, and slows our metabolism.
health consequences of a high pufa diet
Lowers
Metabolic Rate
Lowers Energy
Levels
Impacts
Fertility
Disrupts
Hormones
Increases
Weight Gain
Increases
Stress
Increases
Cellular Damage
Accelerates Skin
Damage & Aging
Disrupts
Gut Health
Weakens
Immune System
Impairs
Carb Utilization
Changes Fats
In Breast Milk
Lowers
Metabolic Rate
Lowers Energy
Levels
Impacts
Fertility
Disrupts
Hormones
Increases
Weight Gain
Increases
Stress
Increases
Cellular Damage
Accelerates Skin
Damage & Aging
Disrupts
Gut Health
Weakens
Immune System
Impairs
Carb Utilization
Changes Fats
In Breast Milk
An important question to ask is: why do PUFAs cause so many health issues?
Because they shift us into hibernation mode.
No, we’re not bears or squirrels — we don’t literally hibernate. But our biology does adjust our metabolic rate based on environmental cues and the foods we consume. And the massive shift in dietary fats has pushed us into a state of subclinical hibernation.
In simple terms, we’re sending the wrong signals to our bodies: winter is coming, food will be scarce — better slow down metabolism and store more fat to survive!
This makes sense for a squirrel prepping for a brutal winter, when they load up on unsaturated fat rich nuts.
But we’re not facing eternal winter — and we definitely don’t have a food shortage.
Instead, we’re living in a state of subclinical hibernation, with sluggish metabolisms, insulin resistance, and fat-storing enzymes running on overdrive — which isn’t helping us feel vibrant, energetic, or thrive.
This downregulation of our metabolism (subclinical hibernation) over the last century isn’t just speculation — it’s documented science, as shown by Dr. John Speakman.(r)
“Basal metabolism may be influenced by many factors one of which is diet. Human dietary changes during the epidemic have included many things such as changes in the amounts of fiber and fat, and the types of fat consumed… The change has been dramatic, as animal fats comprised >90% of the fatty acid intake in 1910 but are currently less than 15%....This suggests that alterations in the intake of saturated relative to unsaturated fat over the last 100 years may have contributed to the decline in BEE reported here”
So, how does the body enter this hibernation-like state?
The metabolic process is complex, but it boils down to how our body listens and responds to the signals we give it — through exposure to light, environmental xenoestrogens like plastics and pesticides, and dietary fat sources. But it's important to remember that the food we eat can modulate gene expression and influence our metabolic state.
When subclinical hibernation mode is triggered by a shift in our dietary patterns, our bodies go into preparation mode for the ‘winter’ ahead. This involves several self-reinforcing mechanisms that lock us into a negative feedback loop. The three main changes are:
- Alters Body Fat Composition
- Increases Harmful Oxidation
- Disrupts Proper Energy Production
Once you understand how these mechanisms work, it becomes clear why PUFAs can negatively affect so many aspects of health — from your body weight, metabolism, and carb burning, to your hormones, skin, immune system, fertility, gut health, and beyond.
1. alters body fat composition
We've become more unsaturated and are not made the same as our great-great grandmas. Quite literally - our body fat is different. It contains more unsaturated fats and less saturated fats. And this shift didn’t happen by accident. It’s a direct reflection of what we eat and how our food is made (which changes our metabolic state).
When in 'subclinical hibernation, the body up regulates enzymes that unsaturates your body fat stores.
Body fat composition reflects the types of fatty acids stored in our fat tissue, and this composition matters. Your body fat and dietary fat is used for fuel. But fat is also used to build cellular structures, hormones, and other critical structures throughout the body. Because saturated and unsaturated fats have different chemical structures, shifting the balance between them can directly impact how your body functions on a cellular level.
This is a classic example of 'you are what you eat'.
If your diet is high in plant-based PUFAs, your body fat composition will reflect that (r,r,r) since this fat composition makeup is shaped by both your diet (r,r) and the activity of enzymes in your body that can turn one type of fat into another.
In one study, adipose tissue linoleic acid increased from 10.9% to 33.7% in individuals adhering to a high-PUFA diet for several years. (r) And a 2015 review paper documented that PUFA levels in body fat, particularly linoleic acid (LA), have continued to rise. (r)
“LA has increased by 136% over the last half century and that this increase is highly correlated with an increase in dietary LA intake over the same period of time…Our findings suggest that adipose tissue LA concentration is strongly correlated with dietary LA intake.” (r)
And for something to go up, something else must go down – saturated fat levels in our bodies have dropped. (r) In other words, we are now less saturated than previous generations, and further from our natural design.
The American diet flipped from high-saturated to high-unsaturated fats - and our body fat has changed with it.
The most unfortunate part is that fats can stick around in your body for a long time. In fact, the half life of linoleic acid is 2 years. Meaning, it takes nearly two years for just half of the LA stored in your fat to be broken down or replaced.
“Because the half-life of LA incorporation into adipose tissue is ~680 d (10), changes in LA intake would take several years to result in a stable increase of adipose tissue LA.” (r)
That’s why reversing the effects of a high-PUFA diet takes time, consistency and intention. If you’re regularly consuming high-LA foods, you’re simply replenishing the stores your body is trying to clear. An occasional indulgence won’t wreck your health, but the foods you eat daily shape your metabolic function and long-term well-being.
In essence, we’re not just consuming calories when we eat fat -- we’re altering the very makeup of our cells and tissues.
This alteration in the structure of our fat stores and cellular structures negatively impacts how our cells and tissues function and lowers our metabolic rates. With the modern diet pushing PUFA consumption to unprecedented levels, it’s worth reconsidering how much and what types of fats we consume to maintain a healthier, more balanced fatty acid profile inside of us.
2. increases harmful oxidation
Not all fats behave the same. PUFAs are uniquely unstable due to their multiple double bonds, which makes them especially prone to oxidation. (r,r) Especially when we are in a subclinical hibernation state. When the balance of fats in the body tips too far toward unsaturated fats and away from saturated fats, oxidative stress can rise - leading to inflammation, cellular damage, and metabolic dysfunction.
Oxidation can occur in two ways: enzymatic, driven by specific enzymes in the body, and non-enzymatic, triggered when PUFAs react with free radicals, oxygen, or other oxidizing agents—particularly under heat or light exposure (a major concern when cooking PUFA-rich foods). This sets off a chain reaction that produces toxic byproducts, which further damage cells and disrupt metabolic processes.
In contrast, saturated fats are chemically stable because they contain no double bonds. This makes them far more resistant to oxidation, and far less likely to generate harmful byproducts in the body or during cooking.
Enzymatic Oxidation - the body's "controlled" use of PUFAs
In enzymatic oxidation, PUFAs are intentionally acted upon by enzymes (like desaturases, COX, and LOX) to modify them into signaling molecules that regulate inflammation and metabolism. While this process is necessary for certain functions, too much PUFA intake can push the body into a chronically inflamed state.
For example, Linoleic Acid (LA), an omega-6 PUFA, is converted by enzymes into arachidonic acid (AA), which is then further metabolized into inflammatory compounds and oxidized linoleic acid metabolites (OXLAMs). These metabolites, including bioactive compounds like 9-HODE and 13-HODE, act as inflammatory signaling molecules that further amplify oxidative damage throughout the body. Elevated levels of OXLAMs are linked to chronic inflammation, oxidative stress, and the development of metabolic diseases. (r,r)
“Lowering dietary LA significantly reduced the abundance of plasma OXLAMs...These results show that lowering dietary LA can reduce the synthesis and/or accumulation of oxidized LA derivatives that have been implicated in a variety of pathological conditions.” (r)
So its best to have less PUFA around to avoid oxidation potential,.
Non-Enzymatic Oxidation: PUFA Breakdown from Oxidative Stress
While enzymatic oxidation is a controlled process, the multiple double bonds in PUFAs make them highly prone to uncontrolled oxidation - especially when exposed to oxygen, free radicals, or heat. This can trigger lipid peroxidation, leading to the breakdown of PUFAs into harmful byproducts.
When free radicals attack PUFAs in cell membranes, fat stores, or the bloodstream, they break apart, producing lipid oxidation products (LOPs) -- toxic compounds that not only serve as biomarkers of oxidative stress but also fuel inflammation and amplify cellular damage (r,r) and are known to be neurotoxic, cytotoxic, and mutagenic. (r,r) These breakdown products disrupt enzymes, degrade proteins, destroy phospholipid structures, and impair cell function, contributing to metabolic dysfunction and long-term health consequences. (r,r)
Think of it like a car crash -- when two vehicles collide, debris flies everywhere, damaging not just the cars involved but also anything nearby. Similarly, when PUFAs oxidize, they generate harmful compounds like 4-HNE (4-hydroxy-2-nonenal), which damages proteins, DNA, and mitochondria, and MDA (malondialdehyde), which promotes inflammation and oxidative stress. Just like how a crash site can leave lasting destruction, the breakdown of oxidized PUFAs can cause widespread cellular damage, accelerating aging and disease processes. In fact, the European Food Safety Authority set a safety limit for MDA at just 30 μg per kg of body weight per day (r), highlighting the potential health risks of these toxic oxidation byproducts.
A quote from Chris Masterjohn, PhD provides another metaphor:
“PUFAs, in this sense, are like delicate glass…When glass shatters, it invariably leaves behind a mess of dangerous shards…Likewise, when PUFAs shatter they leave behind shards such as MDA, which are capable of damaging proteins, DNA and other structurally and functionally important components of our cells. The best way to avoid shattering glass is to be careful with how one uses, cleans and stores it. Nevertheless, the danger of breaking glass will increase simply by having too much of it around. Likewise, the consumption of excess PUFAs increases oxidative stress even when the oils are fresh and properly cared for”.
Research indicates that having less unsaturated fats inside of your body can reduce susceptibility to lipid peroxidation, (r) offering protection against oxidative. Even a modest 5% increase in PUFA content in cell membranes has been shown to result in 16 times more oxidative damage. This phenomenon has been consistently demonstrated in both human and animal studies across a wide range of physiological and pathological conditions. (r,r,r,r,r)
Lipid peroxidation isn’t limited to tissues and the bloodstream—it also occurs during digestion. (r,r) Research suggests that the acidic environment of the stomach can trigger and accelerate this oxidation process (r), especially when pro-oxidant compounds are present, leading to even more lipid peroxides than were in the food to begin with. Also remember, the inside of your body is warm - at or above 98°F - which can promote and sustain lipid oxidation. And the more PUFAs present in a meal, the more oxidation occurs, generating harmful byproducts that your body absorbs. (r)
And this oxidation isn’t limited to inside the body…it starts before the food even hits your plate! Cooking PUFA-rich foods accelerates the formation of toxic compounds like MDA, HNE, and other aldehydes since the high heat initiates oxidation of these unstable fats. (r,r,r) One study showed that the higher the PUFA content in raw meat, the more oxidation products form during cooking. (r) Similarly, eggs higher in PUFA were found to oxidize more easily (r, r. r) reducing their shelf life, and compromising their nutritional value, flavor, and aroma. (r)
That means you’re directly consuming more toxic lipid peroxides—already oxidized and ready to wreak havoc once ingested.
Increasing dietary PUFAs, particularly linoleic acid (LA), and decreasing the saturated-to-unsaturated fat ratio elevates lipid peroxidation throughout the body. (r)
In fact, getting just 15% of your calories from PUFA—which is on the low end for the standard American diet—has been shown to significantly increase oxidative stress markers in healthy men. (r)
On the flip side, lowering linoleic acid intake has been shown to reduce these harmful byproducts. One study found that chronic headache patients who lowered their LA intake from 6.74% to 2.42% of daily calories over 12 weeks not only saw a significant reduction in linoleic acid byproducts but also experienced a dramatic improvement in headache severity and quality of life. (r) These results demonstrate that cutting back on LA could help mitigate inflammation, oxidative stress, and related health issues. (r)
This is why minimizing PUFA intake and choosing fats that are richer in stable, saturated fats can make a meaningful difference. Saturated fats lack the reactive double bonds that make PUFAs so unstable, making them far more resistant to oxidation during cooking, digestion, and inside the body (r) - supporting better metabolic health and less inflammation.
By being intentional with your fat sources, you limit the raw materials that can break down into harmful byproducts—whether during cooking or inside your body.
3. disrupts proper energy production
When in subclinical hibernation, your body downregulates energy production for survival. Why keep the engine running when winter is coming and resources will be scarce?
The upregulation of fat-making enzymes consumes vital oxygen that your cells need for proper energy production. With less oxygen available, your body is left with less capacity to generate energy, which lowers metabolic rates.
Plus, saturated and unsaturated fats have different structures, which means your body processes them differently at the cellular level. Compared to saturated fats, PUFAs “burn dirtier” because of how they move through the mitochondria during energy production.
Your metabolism takes the food you eat and converts it into cellular energy called ATP. But PUFAs generally yield less ATP per unit of carbon than saturated fats, since their multiple double bonds make beta-oxidation less efficient. Unlike saturated fats, which undergo a straightforward breakdown, PUFAs require additional enzymatic steps to bypass these double bonds. This process consumes important resources and ultimately reduces ATP output and our metabolic rate.
The way a fat is built - how many carbon atoms it has and how saturated it is - affects how efficiently your body turns it into energy. Saturated fats, like stearic acid, go through complete beta-oxidation. Each time two carbon atoms are removed, they generate energy-carrying molecules such as FADH₂, which then feed into the mitochondria’s electron transport chain (ETC) to produce ATP, the body’s energy currency.
PUFAs, on the other hand, already contain double bonds, so they skip some steps in this process. For every double bond, one less FADH₂ is made. That means PUFAs generate less energy per carbon and don’t fuel the mitochondria as efficiently.
Because of their structure, PUFAs require more complex steps to be broken down. These extra steps slow the process and increase the chances of electrons leaking out.(r,r) This leakage creates reactive oxygen species (ROS) at the wrong places, which can damage mitochondria and contribute to oxidative stress, insulin resistance, and slower metabolism.
Saturated fats, by contrast, generate more FADH₂ per carbon, which sends electrons into the ETC at Complex II instead of Complex I. This route is cleaner and keeps energy flowing efficiently. It also supports a better cellular redox state (a higher NAD⁺/NADH ratio), which is crucial for a fast and balanced metabolism.
Think of NAD⁺ as an empty taxi ready to pick up electrons (passengers). NADH is the full taxi. If there are too many full taxis and not enough empty ones, everything backs up and energy production slows. Saturated fats help keep more taxis empty and ready, which keeps traffic moving smoothly in your cells.
More energy burned, less energy stored in fat cells.
In short, saturated fats support cleaner, and better energy production with less oxidative damage - leading to higher metabolic rates and less energy storage.
PUFAs burn less efficiently, increase oxidative stress, and suppress metabolic rate—making it easier for the body to store fat.
it didn't used to be this way
Traditional animal fats higher in saturated fats have nourished generations before us. But here’s the catch: animals today are fed very differently than they were 100 years ago - and that changes the fat in the food we eat.
After a century of manipulating food to fit a false health narrative, it’s time to face the truth: the shift in our food’s fatty acid profile is wreaking havoc on our health. It’s time to return to the traditional, nutrient-dense fats that nourished humans for generations. It’s time to send new signals to our bodies — ones that support real energy, metabolic health, and true resilience.
We got so fed up with not being able to find a truly trustworthy source for traditional animal products that we decided to build our own supply chain from the ground up.
At Nourish, we don’t just care about what’s on your plate, we care about the entire process that gets it there. While our beef, lamb, and dairy sheep are 100% grass-fed on pasture - our chickens, pigs, and dairy goats are fed a custom, low-PUFA, corn and soy free diet - designed to support metabolic health and produce meat, eggs, and dairy that are higher in stearic acid and saturated fats, and lower in harmful unsaturated fats. Just like our great-great grandparents enjoyed and drastically different from what’s widely available today. Our goal is to restore a healthier fat balance that mimics how food used to be.
This is food the way it was meant to be - before industrial ag loaded everything with PUFAs. Carefully produced to better support your health and metabolism.
The Nourish LowPs™ Standard
