Does Eating Fat Make You Fat?

As dietary trends constantly evolve, our understanding of the relationship between fat and health has shifted along with them. Many of us grew up with the notion that fat is the enemy, leading to a pervasive fear of incorporating it into our diets. 

This article explores the origins of fat fear and the truth about how they affect our bodies and weight management. Get ready to uncover the science behind dietary fats and learn how to navigate the complex landscape of nutrition for a healthier lifestyle.

Where Does Fat Fear Come From?

Fat fear in America can be traced back to scientific studies from the late 1940s that linked high-fat diets to high cholesterol levels, suggesting a low-fat diet might prevent heart disease. Health experts promoted the low-fat diet not just for high-risk patients but for the entire nation, turning it into an overarching ideology by the 1980s.

The federal government, the food industry, and popular media supported the low-fat ideology, leading to widespread acceptance despite a lack of clear evidence for its effectiveness in preventing heart disease or promoting weight loss.

Early scientific studies linking high-fat diets to heart disease may have been oversimplified, leading to the belief that all fats are equally detrimental to health.

Unfortunately, a lot of the fat fear comes from the incorrect conclusion that because high-fat diets cause diseases in rodents, they do the same in humans.

When rabbits, which are plant eaters, were fed cholesterol, they developed heart disease, which led to the now disproven diet-heart hypothesis.

A lot of cardiovascular and obesity research still relies a lot on rodent models. Researchers feed rats or mice high-fat high-calorie diets, causing various metabolic and gut flora changes that lead to metabolic endotoxemia. As a result, the animals develop obesity, insulin resistance, and numerous other health issues.

But humans are not rodents and the links between fats and health are more nuanced and individualized. In many cases, overeating and being sedentary, regardless of macronutrients, can cause weight gain and other issues rodents get from high-fat high-calorie diets. 

Subsequent clinical research has demonstrated that consuming fat is crucial. While some fats can contribute to health problems, they are essential for good health and play vital roles in various bodily functions.

Does Eating Fat Make You Fat?

The simple answer is no—eating fat without eating too many calories will not make you fat. Weight gain occurs when you consume more calories than your body burns, regardless of whether those calories come from fat, protein, or carbohydrates. You can lose weight on a caloric deficit, whether low-fat, moderate-fat, or eating almost entirely fat.

However, not all calories are created equal. Fat is the most calorie-dense macronutrient, providing nine calories per gram, compared to four calories per gram for protein and carbohydrates. Conversely, fiber varies—soluble fiber has two calories per gram, while insoluble fiber has none.

Because fat is more calorie-dense and makes food taste better, consuming more calories is easier if your diet is high in fat. This can lead to weight gain if you consistently exceed your calorie needs, especially if you’re trying to become exceptionally lean. But simply eating fat in moderation won’t inherently lead to weight gain, especially when paired with nutrient-dense foods and portion control.

Another factor influencing weight you should consider with fat consumption is the thermic effect of food (TEF)—the energy your body uses to digest, absorb, and process nutrients. TEF varies between macronutrients:

• Protein: has the highest TEF, using 20-30% of its four calories per gram.
• Carbohydrates: have a TEF of 5-10% for each of their four calories per gram.
• Fat: has the lowest TEF, between 0-5% of its nine calories per gram.
• Fiber: is especially helpful for dieting, as the body gets only 50% of the four calories per gram from carbs in fiber.

For example, 1,000 calories from protein results in about 700 net calories, while 1,000 calories from fiber nets around 500. On the other hand, 1,000 calories from carbs or fat translate more directly into close to 1,000 “calories in.” This difference in digestion means that high-fat foods might contribute more calories upfront and burn fewer calories during digestion. 

However, fat is still a critical nutrient. The key is moderation and balancing fat with other macronutrients to meet your overall caloric needs without overdoing it.

In short, eating fat won’t make you fat—consuming more calories than your body needs will. Balance, portion control, and understanding the caloric density of fat are essential to maintaining a healthy weight.

“Good” vs. “Bad” Fats

Fat is necessary for a healthy, balanced diet, but it can still be confusing as to which to eat and which to avoid. Let’s clear it up. 

Unsaturated Fats (Eat Plenty)

These are the “good” fats known for supporting heart health, brain function, and overall well-being. One of the most critical concerns regarding fat intake is ensuring adequate intake of essential fatty acids. The two main types of unsaturated fats include:

• Monounsaturated Fats: These fats are found in foods like olive oil, avocados, and nuts, and they help lower bad cholesterol levels and reduce the risk of heart disease.
• Polyunsaturated Fats: These include the essential omega-3 and omega-6 fatty acids, which are crucial for brain function, cell growth, and hormone production. Omega-3s (from fatty fish, walnuts, and flaxseeds) are beneficial for a healthy inflammatory response and supporting heart health. At the same time, omega-6s (from vegetable oils and nuts) are important, too—but maintaining the right balance is crucial.

The exact “healthy” ratio can vary, but it is generally suggested that a lower ratio of omega-6 to omega-3, such as 4:1 or even 1:1, may be beneficial for promoting overall health.

Saturated Fats (Moderate)

These fats are often labeled as “bad,” but the reality is more nuanced. While some research indicates potential metabolic harms of saturated fats, other studies question their potential harm.

The type of saturated fat you consume matters, as its health effects may depend on its origin. A review of studies found that different sources of saturated fats can have varying effects on health due to their unique physical, chemical, and metabolic properties.

For instance, foods like cheese and yogurt, significant sources of saturated fatty acids (SFAs), have been inversely associated with the risk of cardiovascular disease.  In other words, consuming these foods might actually reduce the risk of heart disease rather than increase it, which is the opposite of what people traditionally think about saturated fats.

Researchers believe this is because the health effects of saturated fats are not solely determined by their SFA content but also by other components in the food, such as proteins, minerals, and vitamins, which can modify the impact of SFAs.

Additionally, coconut oil, in particular, has been studied for its effects on cholesterol levels, with virgin processing showing that it does not raise LDL cholesterol. In contrast, refined coconut oil can pose issues for cholesterol levels. Historically, plant-based saturated fats, like those from coconut, that were part of ancient diets have a long-standing presence in human nutrition.

Speaking of coconut oil, MCTs (medium-chain triglycerides) are standout saturated fats you should prioritize. They’re easy for your body to break down and use as a quick energy source, with a lower tendency to be stored as fat.

A meta-analysis of 15 explored the effects of MCT oils on weight loss. Researchers determined that eating a diet enriched with MCTs led to significant weight loss. The weight loss benefits were enhanced when combined with calorie restriction. MCT oil can cause diarrhea if you have too much. It’s also neither calorie-free nor a fat burner, so don’t drink it by the glass or put it on everything.

Saturated fats aren’t for everyone, though. Some genetic factors can play a role in whether or not you should consume them, and yes, that means you may need to avoid MCTs even if Bulletproof coffee seems like a promising health trend. 

Your Genetics and Saturated Fats

Your genes can play a big role in how your body reacts to saturated fats. 

PPARs (Peroxisome proliferator-activated receptors) are proteins that help regulate how your body processes fats, carbohydrates, and proteins. They also help your cells detect fats and insulin, which affects how your body uses and stores energy. There are three types of PPARs—alpha (α), beta (β), and gamma (γ)—each playing a slightly different role in metabolism and fat storage.

For example, if you have a certain version of the PPAR-γ gene (the CC variant), you may be at higher risk for issues like high cholesterol and heart disease when consuming saturated fats. However, people with the GG or GC versions of the gene may not face the same risks.

Your genes also influence how well your body handles saturated fats in other ways. For example:

ACSL1: affects how your body metabolizes saturated fats from animals. If you have weaker variants of this gene, you’re more likely to have poor blood sugar control from eating too much saturated fat, so focusing on plant-based fats may be a better choice.

ADIPOQ: impacts your body’s insulin release and how much adiponectin (a hormone) is produced. If you have lower adiponectin levels, eating red meat and saturated fat may increase your risk of insulin resistance, heart disease, and certain cancers. Boosting omega-3 intake and exercising may help raise adiponectin levels. 

FTO: controls hunger levels and fat storage. Some variants make you feel hungrier and hold on to fat more easily, so eating less saturated fat may help manage weight and hunger.

LPL: determines whether you burn or store saturated fat. If you have the GG variant, your body uses saturated fats for energy more efficiently. Those with other variants (CG or CC) might convert saturated fats into cholesterol more easily.

APOC3: regulates blood triglycerides and LDL cholesterol. Certain gene variants (CC) significantly raise your risk of heart disease when saturated fats are consumed.

APOA2: affects appetite and weight. The C variant can increase appetite and body weight when saturated fat is part of your diet.

While having these genetic variants doesn’t mean you absolutely have to avoid or limit saturated fat, it’s important to be aware of how they may influence your body’s response to certain foods. These genes can be “turned on” or “off” depending on factors like diet, lifestyle, environment, and even gut health. 

Understanding your genetic predispositions allows you to make informed choices that can help optimize your health and reduce potential risks. It’s not about eliminating certain foods entirely, but rather being mindful of what works best for your unique body.

Discover more about how your genes can influence your ideal diet in our article on nutrigenomics.

The most important thing is to follow your body’s feedback. How do you feel eating plenty of saturated fats? How does your blood test look when you try things like a carnivore or keto diet? If you feel great and the test looks optimal, then these diets might be best for you. On the other hand, if you feel bloated and inflamed, or if your blood lipids become suboptimal, then perhaps it’s better to limit saturated fats.

Trans Fats (Avoid)

There is no known safe level of artificial trans fat consumption. These are the real “bad” fats found in many processed and fried foods. You can identify trans fats if the nutrition label includes the words “partially hydrogenated.”

Natural trans fats are also present in ruminant animals’ meat and dairy products like cattle, sheep, and goats. These fats are produced when bacteria in the animals’ stomachs break down grass during digestion. They are likely less harmful than artificial ones, but it’s likely best to keep your consumption to a minimum.

Weight and Fat Intake

Which type of fat you consume may affect your body weight.

A study explored the relationship between various types of dietary fat and long-term weight change in U.S. men and women. Researchers analyzed data from over 120,000 participants over a 20-24 year period through validated questionnaires.

Researchers found a 5% increase in energy intake from saturated fatty acids and a 1% increase from trans-fat were associated with greater weight gain than carbohydrates. Conversely, a 5% increase in energy from polyunsaturated fatty acids was linked to less weight gain. Interestingly, monounsaturated fats from animal sources were associated with weight gain, while those from plant sources were not.

Therefore, different fats impact long-term weight change in varied ways. Replacing saturated and trans-fats with unsaturated fats, particularly polyunsaturated fats, may help prevent age-related weight gain. 

Learn about genetic factors when choosing the best fats for your body in this article. 

Ultimately, what works best for you is individual and based on a variety of factors. This is why BIOptimizers founders Matt and Wade spent years researching, writing, and consulting with doctors and industry experts to develop The Nutrition Bible. It’s a science-backed guide to choosing the ideal foods to eat to live your best life. 

How Much Fat Should You Eat a Day?

Daily fat intake varies based on age, gender, activity level, genetics, health status, and health goals. Current guidelines recommend limiting saturated fat to less than 10% of daily calories—about 20 grams on a 2,000-calorie diet—without suggesting an upper limit on total fat intake.

In contrast, some popular diets advocate for higher fat consumption:

• The ketogenic diet recommends getting 70-80% of daily calories from fat, equating to 155-178 grams per day on a 2,000-calorie diet. 
• The Paleo diet supports higher fat intake from unprocessed sources like avocados, nuts, and fatty meats, suggesting that about 40% of daily calories come from fat while allowing moderate carbohydrate intake.
• The Mediterranean diet features a moderate fat intake of 35-40% of daily calories, primarily from heart-healthy options such as olive oil, nuts, and fish. 

Ultimately, while fat is a necessary part of a healthy diet, the type and amount of fat you consume can vary based on your lifestyle and dietary preferences. Listen to your body’s needs and work with a healthcare practitioner to determine what works best for your optimal well-being. 

If weight loss is a concern, you may want to avoid adding unmeasured amounts of butter, nut butter, or oil to your dishes or beverages. After all, they do have calories. 

Conclusion

The long-standing fear of fat has often overshadowed its essential functions, leading to confusion and misinformed dietary choices. Incorporating healthy fats—such as monounsaturated and polyunsaturated fats—while moderating saturated and avoiding trans fats can significantly impact not only weight management but overall health.

In part 2, of this series, we’ll explore what happens when you don’t eat enough fat. 

Ultimately, navigating the complex landscape of nutrition requires a balanced approach, and resources like The Ultimate Nutrition Bible can guide you through every step, helping you create a sustainable and personalized diet that supports your health goals. 

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