What are fats in simple words?

October 31, 2025 •

4 min read

Did you know that fats contain more than twice the calories per gram as carbohydrates and protein? Despite their high-calorie content, fats are a vital macronutrient that performs many important functions in the body, which is why understanding what are fats in simple words is essential for a balanced diet.

Quick Summary

Fats are a macronutrient that the body uses for energy, cell function, and vitamin absorption. They are classified into types like saturated, unsaturated, and trans fats, which affect health differently. Choosing healthier unsaturated fats while limiting unhealthy saturated and trans fats is key for overall well-being.

Key Points

Essential Macronutrient: Fats are one of the three main macronutrients, alongside proteins and carbohydrates, and are essential for bodily functions.
Energy and Storage: Your body uses fat as a major source of energy and a storage depot for excess calories.
Good vs. Bad Fats: Unsaturated fats (like those in olive oil and fish) are considered 'good,' while saturated and trans fats are considered 'bad' for heart health.
Key Functions: Fats are crucial for absorbing fat-soluble vitamins (A, D, E, K), insulating the body, and building cell membranes.
Focus on Substitution: Improving your diet involves replacing unhealthy fats with healthier options, not eliminating all fats.

Fats, or lipids, are a type of nutrient that the body uses for several critical functions, from energy storage to creating hormones. While often demonized, the key is understanding the different types and how they impact your health. By breaking down the complex science, it's easy to grasp what fats do and how to incorporate them wisely into your diet.

The Three Main Types of Fats

Fats are not all the same. They are primarily categorized based on their chemical structure, which determines their physical properties and health effects. Most foods contain a mix of different types of fats, but are classified based on the dominant kind.

Unsaturated Fats: The 'Good' Fats

Unsaturated fats are typically liquid at room temperature and are considered beneficial for health when consumed in moderation. They can help lower bad (LDL) cholesterol and support heart health. This category is further divided into two types:

Monounsaturated Fats (MUFAs): Found in plant-based oils, nuts, and avocados, these can help maintain healthy cholesterol levels.
Polyunsaturated Fats (PUFAs): These include essential fatty acids like omega-3s and omega-6s, which the body cannot produce on its own. They are found in fish, walnuts, and flaxseeds and are crucial for brain function and reducing inflammation.

Saturated Fats: The 'Limit' Fats

Saturated fats are typically solid at room temperature and are primarily found in animal products. While some saturated fat is needed in the diet, excessive intake can raise levels of bad (LDL) cholesterol, increasing the risk of heart disease. Sources include fatty meats, butter, cheese, and tropical oils like coconut and palm oil. Health recommendations suggest limiting saturated fat intake rather than eliminating it entirely.

Trans Fats: The 'Bad' Fats

Trans fats are the most harmful type of fat and should be avoided as much as possible. They can raise bad (LDL) cholesterol and lower good (HDL) cholesterol, significantly increasing the risk of heart disease, stroke, and type 2 diabetes. Most artificial trans fats are created through a process called hydrogenation, which turns liquid oils into solid fats for longer shelf life. They are often found in processed and fried foods.

Why Your Body Needs Fats

Beyond being a concentrated energy source, fats are involved in a number of critical bodily processes. A moderate amount is essential for maintaining overall health.

Functions of Fats in the Body

Energy storage: Fats are the most energy-dense macronutrient, providing 9 calories per gram. They act as the body's long-term fuel reserve, stored in fat cells (adipose tissue) for future use when food is scarce.
Vitamin absorption: Certain vitamins, specifically A, D, E, and K, are fat-soluble and can only be absorbed and transported throughout the body with the help of fat.
Organ protection and insulation: Fat tissue insulates the body against cold and cushions vital organs, protecting them from physical shock.
Cell building: Fats are a key structural component of all cell membranes, which control what enters and leaves a cell.
Hormone production: Fats are necessary for the production of hormones that regulate various bodily functions.

A Comparison of Good vs. Bad Fats

Knowing the differences between fats can help you make informed dietary choices. Here is a simple comparison to help distinguish between healthy and unhealthy fats:


Aspect	Good Fats (Unsaturated)	Bad Fats (Saturated & Trans)
Physical State	Typically liquid at room temperature (oils)	Typically solid at room temperature (butter, lard)
Sources	Plant oils (olive, canola), nuts, seeds, avocados, fatty fish	Animal products (red meat, dairy), processed foods, baked goods
Cholesterol Impact	Can lower bad (LDL) cholesterol and raise good (HDL) cholesterol	Raises bad (LDL) cholesterol
Heart Health	Improves heart health and reduces risk of heart disease	Increases risk of heart disease and stroke
Essential for Body	Includes essential fatty acids (Omega-3, Omega-6) the body cannot make	Not essential for body, excess intake is detrimental

Making Healthy Fat Choices

Making smarter choices about the fats you eat doesn't mean you have to abandon your favorite foods entirely, but rather focus on moderation and substitution.

Practical Tips for a Healthier Diet

Use healthy oils for cooking: Swap butter or lard for olive or canola oil when cooking.
Add healthy fats to meals: Top salads with nuts, seeds, or avocado. Add a side of fatty fish, like salmon, to your dinner menu.
Choose lean protein sources: Select lean cuts of meat and remove skin from poultry to reduce saturated fat intake.
Read food labels: Look for foods with little to no trans fat and lower saturated fat percentages. Avoid products listing “partially hydrogenated oil” as an ingredient.
Snack smarter: Instead of chips or pastries, opt for a handful of nuts, a spoonful of nut butter, or seeds.

The Bottom Line

In simple terms, fats are a diverse group of compounds essential for life, not simply something to be avoided. A balanced diet requires a mindful approach to fat consumption. Prioritizing healthy unsaturated fats from plant and fish sources while minimizing unhealthy saturated and trans fats is the most effective strategy for promoting long-term health. The goal is not to go fat-free, but to choose wisely for a well-rounded and nutritious diet.

For more detailed dietary guidance and a heart-healthy plan, consider exploring the DASH Eating Plan from the National Heart, Lung, and Blood Institute.

Conclusion

Understanding what fats are in simple words demystifies this often-misunderstood nutrient. Fats are a necessary and high-energy part of our diet that serve many vital functions, from providing energy to absorbing key vitamins. The crucial distinction lies between good, unsaturated fats and bad, saturated and trans fats. By choosing more monounsaturated and polyunsaturated fats while limiting saturated and avoiding trans fats, you can support heart health and overall well-being. A balanced, mindful approach to dietary fat is the most effective way to reap its benefits without the associated health risks.

Frequently Asked Questions

Saturated fats are typically solid at room temperature and mainly come from animal products, like butter and red meat. Unsaturated fats are usually liquid at room temperature and are found in plant-based sources, including olive oil, nuts, and seeds.

No, not all fats are bad. Healthy fats, known as unsaturated fats, are essential for your body to function properly, aiding in vitamin absorption and supporting brain and heart health. The key is to consume healthy fats in moderation and limit unhealthy saturated and trans fats.

Trans fats are a type of artificial fat created through a process called hydrogenation to give foods a longer shelf life. They are particularly unhealthy because they raise bad (LDL) cholesterol and lower good (HDL) cholesterol, increasing the risk of heart disease.

To identify trans fats, check the nutrition label for products that list 'partially hydrogenated oil' as an ingredient. Many processed and fried foods once contained high levels of trans fats, though regulations have reduced their use.

Yes, fats are necessary for the absorption of fat-soluble vitamins, which include vitamins A, D, E, and K. Without a moderate amount of fat in your diet, your body cannot properly utilize these important nutrients.

Yes, all fats, regardless of type, are high in calories (9 calories per gram). Consuming more calories than your body needs, even from healthy fats, can lead to weight gain. Moderation is key to a healthy diet.

Good sources of healthy, unsaturated fats include avocados, nuts (like almonds and walnuts), seeds (like flax and chia), fatty fish (such as salmon and mackerel), and plant-based oils (like olive and canola oil).