What Do Oils Do to Your Body? Understanding Fat's Essential Role

December 7, 2025 •

4 min read

While oil is 100 percent fat, the term 'healthy cooking oil' is not a misnomer, as different oil types play diverse roles in the body's health. This guide will explore exactly what do oils do to your body and how different fat compositions dictate their impact on your health, energy, and cellular function.

Quick Summary

Oils are vital for providing energy, absorbing fat-soluble vitamins, and forming cell membranes, though the specific type of oil is crucial. Unhealthy fats can raise bad cholesterol and cause inflammation, while healthy fats offer anti-inflammatory and cardioprotective benefits.

Key Points

Energy Source: Oils are a highly concentrated source of energy, providing 9 calories per gram, which is more than double the energy from carbohydrates or protein.
Nutrient Absorption: Fats are essential for absorbing fat-soluble vitamins (A, D, E, and K), which are vital for functions like vision, bone health, and immune support.
Cellular and Hormonal Health: Essential fatty acids from oils are critical for building healthy cell membranes and producing hormones that regulate various bodily processes.
Cholesterol Management: Unsaturated fats (monounsaturated and polyunsaturated) help lower 'bad' LDL cholesterol, while excessive saturated and trans fats can raise it, increasing heart disease risk.
Dietary Balance: Both too much and too little oil can cause health problems, such as obesity, liver issues, and vitamin deficiencies. The key is moderation and choosing healthier oil types.

The Fundamental Functions of Oils in the Body

Far from being solely a source of calories, fats and oils perform several indispensable functions that are crucial for survival and overall health. They are concentrated sources of energy, containing 9 calories per gram, which is more than double that of carbohydrates or protein. This high energy density makes them an efficient fuel source, particularly when glucose levels are low.

Essential Nutrients and Vitamin Absorption

One of the most critical functions of oils is their role in nutrient absorption. Certain vitamins—specifically A, D, E, and K—are fat-soluble, meaning they require dietary fats to be absorbed properly by the body. Without enough fat in the diet, the body cannot absorb these vitamins, leading to potential deficiencies that can impact vision, bone health, immune response, and blood clotting.

Cellular and Hormonal Structure

Oils and fats provide essential fatty acids, such as omega-3 and omega-6, which the body cannot produce on its own and must obtain from food. These fatty acids are integral to the structure of every cell membrane in the body, which dictates how cells interact with each other and their environment. Additionally, they serve as building blocks for hormones that regulate a wide range of bodily functions, including mood and appetite.

The Impact of Different Oil Types on Health

Not all oils are created equal. The type of fat—saturated, monounsaturated, or polyunsaturated—determines its effect on cholesterol levels and chronic disease risk. The right balance is key to maintaining a healthy lipid profile.

The 'Good' Fats: Unsaturated Oils

Unsaturated fats are generally considered heart-healthy and are typically liquid at room temperature. They are primarily sourced from plants and fish.

Monounsaturated Fats (MUFAs): Found in olive oil, avocado oil, and many nuts, MUFAs can help lower LDL ('bad') cholesterol levels while maintaining or increasing HDL ('good') cholesterol. Extra virgin olive oil also provides antioxidants with anti-inflammatory properties.
Polyunsaturated Fats (PUFAs): These include omega-3 and omega-6 fatty acids. Omega-3s, found in sources like fish oil and flaxseed oil, are known for their anti-inflammatory effects and ability to lower blood triglycerides. Omega-6s are abundant in many common vegetable oils (sunflower, soybean, corn), but should be consumed in moderation to maintain a healthy balance with omega-3s.

The 'Bad' Fats: Saturated and Trans Fats

Saturated and trans fats have been linked to negative health outcomes, primarily related to heart health.

Saturated Fats: Found in animal products like butter and lard, as well as tropical oils such as palm and coconut oil. Excessive intake of saturated fat can increase LDL cholesterol, contributing to arterial plaque buildup.
Trans Fats: These are often formed during the partial hydrogenation of vegetable oils to give them a longer shelf life. Artificial trans fats are particularly harmful, as they both raise LDL cholesterol and lower HDL cholesterol.

Oil Metabolism in the Body

When you consume oils, the body breaks them down through a series of metabolic processes. Digestion begins in the mouth and continues in the small intestine, where pancreatic lipases and bile salts break down triglycerides into smaller fatty acids and monoglycerides. These are then absorbed by intestinal cells and reassembled into triglycerides, which are packaged into lipoproteins called chylomicrons for transport through the lymphatic system and bloodstream.

Once in circulation, the fatty acids can be used for immediate energy through a process called beta-oxidation. Excess fatty acids are stored in adipose tissue for future use. When the body needs energy and glucose is scarce, stored triglycerides are broken down into fatty acids and glycerol.

The Consequences of Dietary Imbalance

Both insufficient and excessive intake of oils can have significant health repercussions.

Too Much Oil

Overconsumption of oil, especially unhealthy fats, leads to a surplus of calories, promoting weight gain and obesity. A diet high in saturated and trans fats can elevate cholesterol levels, increasing the risk of heart disease, stroke, and type 2 diabetes. It can also contribute to non-alcoholic fatty liver disease (NAFLD) and trigger chronic inflammation.

Not Enough Oil

On the other hand, cutting out all fat, particularly healthy oils, can hinder the absorption of fat-soluble vitamins (A, D, E, K), leading to potential deficiencies. Insufficient fat intake can disrupt hormone production, cause digestive discomfort, and result in skin problems like dryness. Since fats also contribute to satiety, a very low-fat diet may lead to increased hunger and cravings.

Comparison of Common Edible Oils


Feature	Olive Oil (Extra Virgin)	Coconut Oil	Canola Oil	Sunflower Oil
Fat Composition	High in monounsaturated fats	Very high in saturated fats	High in unsaturated fats (Omega-3/6)	Predominantly polyunsaturated fats (Omega-6)
Health Effects	Lowers LDL, raises HDL, anti-inflammatory	Increases both LDL and HDL; health benefits inconclusive	Helps lower cholesterol	Helps lower LDL, but high Omega-6 can be inflammatory
Best for Cooking	Low to medium heat sautéing, dressings	High heat cooking, best used sparingly	All-purpose cooking and baking	Frying and high-heat applications
Nutrients	Vitamins E, K, antioxidants	Lauric acid	Vitamins K, E	Vitamin E, Omega-6

Conclusion: Finding the Right Balance

Oils are a vital and necessary component of a healthy diet, providing energy, essential fatty acids, and aiding in vitamin absorption. Their impact on your body, however, depends heavily on the type and quantity consumed. By prioritizing plant-based unsaturated oils and using saturated fats sparingly, you can manage cholesterol, reduce inflammation, and support overall health. A balanced approach, focusing on wholesome sources of fats rather than completely eliminating them, is the most effective strategy for long-term well-being.

For more detailed information on cardiovascular health recommendations, visit the American Heart Association at https://www.heart.org/.

Frequently Asked Questions

Saturated fats are typically solid at room temperature and found in animal products and some tropical oils, increasing bad cholesterol levels. Unsaturated fats, usually liquid at room temperature and sourced from plants and fish, are healthier and can help lower cholesterol.

The body cannot produce essential fatty acids like omega-3 and omega-6 on its own, so they must be obtained from the diet. They are crucial for building cell membranes, producing hormones, and supporting brain and heart function.

Excessive oil consumption, particularly of unhealthy fats, can lead to weight gain, high cholesterol, increased risk of heart disease and type 2 diabetes, digestive issues, and fatty liver disease.

A diet with too little fat can impair the absorption of fat-soluble vitamins (A, D, E, K), disrupt hormone production, and cause skin problems like dryness.

Oils are broken down by enzymes called lipases with the help of bile salts in the digestive system. The resulting fatty acids are absorbed, reassembled into triglycerides, and transported for energy or storage. For energy, they are oxidized into acetyl CoA.

Oils rich in monounsaturated or polyunsaturated fats are generally the healthiest choices. Good examples include extra virgin olive oil for low-to-medium heat cooking and canola, rice bran, or avocado oil for higher heat applications.

Yes, unhealthy fats can lead to insulin resistance, impairing the body's ability to regulate blood sugar. In contrast, some studies show that oils like olive and sesame oil may improve blood sugar control.