Fact-checked by Dr. Anthony Gustin, DC, MS.
Written by Lorenz Mac
The theory that eating fat makes you gain weight has been debunked by science several times over. Sadly, many people still believe that fat consumption is the reason why so many of us are overweight.
If we look at it from a caloric perspective, it would make sense to think that dietary fat would make you gain weight because it contains nine calories per gram versus the four calories in carbohydrate and protein.
So wouldn’t eating less fat make you lose weight?
Not necessarily. This theory alone plays a huge role in our obesity epidemic.
Your metabolism is much more complicated and the vast network of organisms juggle thousands of duties using food to control each process.
Understanding that nutrition isn’t a simple equation of calories in versus calories out is a step forward towards a more nutritionally knowledgeable, healthier population.
A donut from your local bakery may have the same amount of calories as an avocado and macadamia nuts but the difference in how your body uses those calories is night and day. And the same amount of fats from an effective energy source like MCT oil compared to vegetable oils can drastically improve your energy levels.
In this article, we’ll talk about:
The idea that eating fat makes you gain weight started back in the 1950s when a doctor named Ancel Benjamin Keys conducted a large study showing that the overconsumption of fat had contributed to the heart disease epidemic at the time.
Ever since, America has been taught to believe that fat is responsible for heart disease, clogged arteries and obesity.
Americans started avoiding fatty foods like cheese, meat, butter, nuts and even avocados. Because of this, the food industry had to start coming up with different ways to make food taste good while maintaining low fat content.
Manufacturers began replacing fat with sugar ingredients to increase the palatability of food. This is when the rise of low fat, high carbohydrate foods began.
Many foods were being marketed as “low-fat” but when you look at the nutrition label, you’ll see that it’s substituted with alarmingly high levels of sugar.
But now that we know fat is actually healthy for you when consumed from healthy sources, it’s time that we take the proper steps to fix our diets as a population.
Food affects your body’s gene expression which either cause or prevent disease. This means food literally has the power to either turn on your health gene or your disease gene. It signals those genes to store fat on your body or to burn it off as energy.
The food you eat is directly responsible for regulating your hormones, your brain chemistry, gut microbiome and immune system.
Studies have shown the type of food we consume regularly plays a significant role in shaping the microbiome as well as modulating risk of chronic diseases[*].
So what makes us fat if it isn’t fat?
Insulin is the most important factor when it comes to gaining weight. When you gain body fat, your body begins to produce more of the hormone leptin, telling your body to stop gaining weight.
This is a survival mechanism because an obese human or animal who can’t move well won’t make it out alive.
Leptin and insulin are hormones that are the opposite of each other. While one tells the body to store body fat, the other is telling it to stop.
When we continue to eat fructose (sugar), it causes insulin resistance and chronically high levels of insulin which also stimulates higher levels of leptin. This causes your body to develop a leptin resistance which is common amongst people who are obese.
People who are a healthy body weight are leptin sensitive and those who are obese are leptin resistant[*].
There are only two sources of fuel that our body can burn for energy, from sugar (carbohydrates) or fat.
When you eat excess protein or carbohydrates, it goes through the liver — stimulates insulin — which tells the body to starn burning sugar and storing the rest as fat or glycogen.
Dietary fat works differently. Instead, it’s absorbed in your body’s intestines as chylomicrons, goes through your lymphatic system and directly into the body’s systemic blood circulation instead of through the liver.
From there, it’s stored into the fat cells. This means that fat does not affect the liver meaning it doesn’t need any assistance from insulin and goes directly into fat stores.
Doesn’t that mean fat makes you fat? Not at all.
When you begin to eat more fats — it gets stored into fat cells — but insulin doesn’t go up.
As fat mass increases, leptin also goes up. And since lean, healthy people are leptin sensitive, they would stop eating to let their body weight go back down.
When you eat additional calories from fat, your body will ramp up its metabolism to burn off the extra calories, if you are primarily using fat as energy with the absence of carbohydrate.
People who are obese and leptin resistant may not experience the same metabolic advantage as people who are already low in body fat.
As you eat large amounts of fat as an obese person, insulin doesn’t go up but the additional dietary fat will go directly into your fat stores.
Your body increases leptin levels in the blood but the difference is, your body doesn’t care. It’s resistant to the effects of leptin so your metabolism doesn’t go up, your appetite doesn’t go down and you don’t experience the same weight loss benefits as someone who is already lean.
But this doesn’t mean carbohydrates should be the alternative for an obese person.
Instead, focusing on completely restricting your carbohydrate intake and using fats as your main source of energy will prime your body into receiving the same health benefits as people who are already lean.
This is also known as ketosis. Once your body prefers fat as fuel rather than carbohydrate (glucose), you will begin to experience regulated insulin and leptin hormonal functioning, decreased appetite and faster weight loss.
Following a ketogenic diet will help people who are overweight to start burning both dietary and body fat as energy rather than storing it.
Eating Fat Helps You Burn Calories
A study by conducted by the National Institutes of Health found that with all other factors being identical — exercise regimen, sleep schedule, caloric intake — that those who ate more fat compared to an identical amount in calories in carbs burned over 100 more calories a day.
The study also found that eating more fat turns off your brain’s hunger hormone. Overall, the researchers concluded that eating healthy dietary fats over carbohydrates is more effective in weight loss[*].
The body requires fat to run properly. It’s a required macronutrient for building cell membranes and the protective shields around us. When we don’t eat fat, we begin to crave calories in the form of refined carbohydrate and sugar, which are both linked to weight gain and obesity.
Another study followed human participants over a 12 month period comparing a low fat diet with a high carbohydrate diet.
Over the 12 month period, results showed that the high fat diet had[*]:
- Better triglyceride levels
- Improved HDL cholesterol
- Greater decreases in fat mass
The main driver of weight gain is insulin. When your body cannot process insulin correctly, processed carbs such as bread and sugar begin to spike your insulin levels.
Insulin then drives the fuel in your bloodstream into your fat cells which also stimulates your brain to eat more food.
Additionally, when you try to eat at a calorie deficit and exercise more frequently — the common regimen to weight loss — your body goes into a starvation mode. This makes you more tired, slows down your metabolism and makes you hungrier.
The starvation mode is a natural physiological response and the scientific term for it is adaptive thermogenesis[*].
This is why the “eat less and workout more” regimen is flawed.
Why Too Much Carbohydrate Can Be the Real Culprit
Carbohydrates are known as the most addictive food group. In fact, consuming sugar lights up the same reward centers as someone doing drugs like cocaine.
What makes matters worse is, sugar is contained in the majority of packaged foods in the market. Common household foods like cereal, energy drinks and salad dressing all have an excess amount of sugar.
Unlike healthy fats, sugar doesn’t fill you up or improve your metabolism.
Instead, it will spike your insulin levels for a short period of time, leaving you hungry an hour or two after a sugar-laden meal. This also turns into excess fat on the body and in more serious cases can turn into type 2 diabetes.
The World Health Organization recommends around 30 grams or less of sugar a day. Just one cup of orange juice has around the same amount.
Too much carbohydrate will weaken your insulin sensitivity. This is the main reason why your body will begin to store excess carbohydrate into fat rather than used as energy.
Several studies show that people who eat low carb, high fat diets have a much faster metabolism compared to low fat high carbohydrate diets.
One study showed that the higher fat diet groups had a faster metabolism whereas the high carbohydrate groups experienced consistent insulin spikes which was a contributing factor to a slower metabolism[*].
Another study conducted on human participants compared a high fat, low carb group with a low fat high carb diet in a “controlled feeding study” where the scientists provided all the food.
The results once again concluded that the high fat group had greater metabolic advantages.
The same researched proceeded to do a crossover trial. This is where you use the same participants to test different diets.
They flipped the diets for the second part of the study. This allowed the researchers to study the effects on metabolism on the same person but with different diets.
Once again, the high fat group ended up burning more calories than the low fat group. The high fat group also had large improvements in cholesterol as well as improvements with insulin resistance[*].
Eating Healthy Fats Will Improve Your Life
The bottom line is that fats should be an one of the main food groups in your diet when looking to increase longevity and improve your body’s metabolism.
Following a low carbohydrate, high fat ketogenic diet has been proven to be more effective in losing weight and regulating hormones over the standard low fat, high carbohydrate diet.
The low fat myth has been disproven by science and it’s time we start looking at the real culprit to obesity and fat gain, carbohydrates.