Why is it necessary for humans to eat fat? Dispelling myths and revealing vital functions

October 31, 2025 •

3 min read

The human brain is made up of nearly 60% fat, highlighting just how fundamental dietary fats are to our physiology. So, why is it necessary for humans to eat fat? Far from being harmful, consuming the right types of fat is essential for providing energy, protecting organs, and enabling key bodily processes.

Quick Summary

Fats are a vital macronutrient that provides energy, supports cell growth, produces essential hormones, and facilitates the absorption of fat-soluble vitamins like A, D, E, and K. The body cannot produce certain essential fatty acids, which must be obtained through the diet.

Key Points

Essential for Energy: Fats provide a concentrated source of energy, offering 9 calories per gram, and serve as an important long-term energy reserve.
Nutrient Absorption: Dietary fat is necessary for the proper absorption of fat-soluble vitamins A, D, E, and K, which are essential for vision, bone health, and other vital functions.
Brain Health: Fats are a major structural component of the brain and nervous system, crucial for cognitive function, nerve cell membranes, and impulse transmission.
Hormone Production: Fats, particularly cholesterol, are building blocks for essential hormones, including sex hormones and stress-regulating hormones.
Cell Structure and Protection: Fats provide structural integrity for cell membranes and serve as protective insulation for vital organs.
Fat Quality Matters: Focusing on healthy unsaturated fats (found in nuts, seeds, avocados, olive oil) while minimizing unhealthy saturated and trans fats is key to a balanced diet.

For decades, fat was viewed negatively, often linked to weight gain and heart problems, leading to a focus on low-fat diets. However, research now shows that the type of fat consumed is more important than avoiding it entirely. Eliminating fat from the diet can deprive the body of essential nutrients and lead to various health issues.

The Multifaceted Roles of Fat in the Human Body

Energy and Storage

Fats are a primary energy source, providing 9 calories per gram, which is more than double that of carbohydrates or protein. This energy fuels daily activities and metabolic functions. Excess energy is stored as body fat, providing an energy reserve and insulating organs.

Essential Fatty Acids

The body cannot produce omega-3 and omega-6 fatty acids, making them essential components of the diet. These polyunsaturated fats have distinct but crucial roles.

Omega-3s: Important for brain function, nerve development, and vision, and known for anti-inflammatory properties. Found in fatty fish, flaxseed, and walnuts.
Omega-6s: Involved in immune system regulation and producing hormone-like substances. Common in vegetable oils, nuts, and seeds.

Hormone Production and Regulation

Fats are essential for producing many hormones, including sex hormones, with cholesterol acting as a precursor for steroid hormones. Sufficient dietary fat supports hormonal balance, while adipose tissue produces hormones like leptin, which helps regulate appetite.

Vitamin Absorption

Fat-soluble vitamins (A, D, E, and K) require dietary fat for proper absorption and transport. Without enough fat, the body cannot effectively use these vitamins, potentially leading to deficiencies. Including healthy fats with vitamin-rich foods can enhance nutrient uptake.

Brain and Nerve Function

The brain is largely composed of fat (about 60%). Fats are vital for healthy cell membranes in the brain and nervous system, which are crucial for nerve impulses and memory. Omega-3 fats are particularly associated with better cognitive function and may reduce the risk of cognitive decline.

Structural Integrity and Satiety

Beyond being a cell membrane component, fats enhance food flavor and aroma. They also promote satiety, helping regulate appetite due to slower digestion compared to carbohydrates and protein.

Understanding Different Types of Fat

Different types of fat have varying effects on health. The table below outlines the main types and their sources and impacts.


Type of Fat	Health Impact	Common Sources
Unsaturated Fats (Monounsaturated)	Improve cholesterol levels Reduce heart disease risk	Avocados, nuts (almonds, peanuts), olive oil
Unsaturated Fats (Polyunsaturated)	Lower LDL ('bad') cholesterol Provide essential fatty acids	Fatty fish, flax seeds, walnuts, corn oil
Saturated Fats	Can raise LDL cholesterol if consumed in excess	Fatty meats, butter, cheese, coconut oil
Trans Fats	Raise LDL and lower HDL ('good') cholesterol Harmful to heart health	Fried foods, baked goods (containing partially hydrogenated oils)

Sourcing Healthy Fats for Your Diet

Prioritize incorporating healthy, unsaturated fats into your diet while limiting saturated and avoiding artificial trans fats. The quality of fat is crucial.

Here are some practical ways to include healthy fats:

Use olive oil for cooking and in dressings.
Include fatty fish in your meals weekly.
Snack on nuts like walnuts or almonds.
Add avocado to dishes.
Sprinkle flaxseeds or chia seeds on food.
Choose nut and seed butters.

The Risks of a Low-Fat Diet

A diet too low in fat can lead to issues such as poor absorption of fat-soluble vitamins. When fat is removed from processed foods, it's often replaced with sugars, potentially increasing the risk of metabolic problems. Lack of fat can also reduce satiety, potentially leading to overeating. A balanced diet focusing on nutrient-dense whole foods is recommended.

Conclusion

Fat is a vital macronutrient essential for numerous bodily functions, including providing energy, absorbing vitamins, and forming hormones and cell structures. It is crucial to choose healthy unsaturated fats over saturated and trans fats. By focusing on the quality of fat intake, individuals can support overall health. For further information, The Nutrition Source at Harvard's T.H. Chan School of Public Health is a valuable resource.

Frequently Asked Questions

Essential fatty acids are omega-3 and omega-6 fats that the body cannot produce on its own. They must be obtained through your diet and are crucial for brain function, hormone regulation, and cell health.

No, a very low-fat diet can lead to health problems, including deficiencies in fat-soluble vitamins and hormonal imbalances. Focus on replacing unhealthy fats with healthy ones rather than eliminating fat entirely.

Excellent sources of healthy fats include avocados, olive oil, nuts (like walnuts and almonds), seeds (like flax and chia), and fatty fish (like salmon and mackerel).

Fats are required to absorb and transport fat-soluble vitamins (A, D, E, K). They dissolve in fat during digestion, allowing them to enter the bloodstream. Without fat, these vitamins cannot be effectively utilized by the body.

Yes. All fats, regardless of their type, are high in calories (9 calories per gram). While healthy fats are beneficial, they should still be consumed in moderation as part of a balanced diet to maintain a healthy weight.

You should minimize your intake of saturated fats and strictly avoid artificial trans fats. Trans fats are highly detrimental to heart health and can be found in many processed and fried foods.

Try simple swaps like using olive oil for cooking, adding avocado to sandwiches, topping salads with nuts or seeds, and having a handful of nuts as a snack instead of processed items.