Which Fatty Acids Are Not Healthy? The Definitive Guide to Bad Fats

November 16, 2025 •

4 min read

According to the World Health Organization (WHO), over 278,000 deaths annually are attributed to industrially produced trans fats. To protect your long-term health, it is crucial to understand which fatty acids are not healthy, particularly industrial trans fats and excessive saturated fats, and how to identify and avoid them.

Quick Summary

Industrial trans fats and excessive saturated fats are the primary unhealthy fatty acids to limit or avoid in your diet. These fats can negatively impact cholesterol levels, increase inflammation, and raise the risk of heart disease and other health issues.

Key Points

Industrial Trans Fats are the worst: Artificially created trans fatty acids from partially hydrogenated oils are the most harmful fats, increasing bad cholesterol and lowering good cholesterol.
Saturated Fats are less healthy in excess: Found in animal products and some tropical oils, excessive saturated fat intake raises bad cholesterol and should be limited.
Check for Hidden Trans Fats: Always read food ingredient lists for 'partially hydrogenated oil,' even if the label claims 'zero trans fat'.
Replace Bad Fats with Good Fats: Swap saturated and trans fats for healthier monounsaturated and polyunsaturated fats found in olive oil, nuts, seeds, and fish.
Prioritize Whole, Unprocessed Foods: Reducing processed snacks, fast food, and commercially baked goods is the most effective way to decrease your intake of unhealthy fats.

The Health Dangers of Unhealthy Fatty Acids

Fatty acids are the building blocks of the fats we consume, and they have diverse effects on our health. While some fatty acids are essential for bodily functions, others, when consumed in excess, can have detrimental effects on cardiovascular health and overall well-being. The two main culprits are trans fats and saturated fats.

Industrial Trans Fatty Acids: The Worst Offenders

Trans fats, or trans-fatty acids (TFA), are widely considered the most dangerous type of fat for human consumption. The majority of trans fats are produced through an industrial process called partial hydrogenation, which turns liquid vegetable oils into solid fats to increase their shelf life.

Impact on Cholesterol: Unlike other fats, industrial trans fats simultaneously raise low-density lipoprotein (LDL or 'bad') cholesterol and lower high-density lipoprotein (HDL or 'good') cholesterol levels. This combination is highly damaging and contributes significantly to the buildup of fatty plaques in the arteries, a process known as atherosclerosis.
Increased Cardiovascular Risk: The negative effect on cholesterol greatly increases the risk of heart attack, stroke, and other cardiovascular diseases. The WHO attributes a significant number of yearly deaths to industrial trans fat intake.
Inflammation: Studies also link trans fats to increased inflammation in the body, which is a key driver of heart disease and other chronic conditions like diabetes.
Hidden Sources: Despite being largely banned in many countries, trans fats can still appear in processed foods under names like 'partially hydrogenated oil'. Always check ingredient lists for this term.

Excessive Saturated Fatty Acids: A Moderate Risk

Saturated fats are another type of fatty acid that, when consumed excessively, can negatively affect health. Found primarily in animal products and some tropical oils, saturated fats are typically solid at room temperature.

Effect on Cholesterol: Like trans fats, saturated fats can raise LDL ('bad') cholesterol levels. The American Heart Association recommends limiting saturated fat to less than 6% of total daily calories.
Debate and Nuance: The health implications of saturated fat have been subject to ongoing debate. Some newer research suggests that the risk of heart disease from saturated fat may be less pronounced than previously thought, especially when compared to the undeniable harm of trans fats. However, most health organizations continue to recommend limiting intake and replacing saturated fats with healthier unsaturated options.
Whole Food Context: The overall food context matters. Saturated fat from a processed meat product is different from the fat found in a piece of full-fat cheese, which may contain other beneficial nutrients.

A Comparison of Unhealthy Fatty Acids

To clarify the differences, here is a comparison of industrial trans fats and saturated fats.


Feature	Industrial Trans Fats (iTFAs)	Excessive Saturated Fats
Primary Source	Artificially created via partial hydrogenation of vegetable oils.	Naturally occurring in animal products (meat, dairy) and some tropical oils.
Physical State	Solid or semi-solid at room temperature.	Typically solid at room temperature.
Cholesterol Impact	Raises LDL, lowers HDL; extremely harmful.	Raises LDL, but less damaging than trans fats; does not lower HDL.
Health Consensus	Universally recognized as harmful with no health benefits; intake should be avoided.	Health impact is debated but consensus remains to limit intake.
Primary Risk	High risk of cardiovascular disease, inflammation, and stroke.	Increased risk of heart disease when consumed in excess.

How to Reduce Unhealthy Fatty Acids in Your Diet

Mitigating the intake of unhealthy fatty acids involves mindful eating and smart substitutions. Instead of focusing solely on elimination, aim to replace bad fats with healthier alternatives. For example, switch from cooking with butter to using olive oil, or choose lean protein sources over fatty red meats.

Prioritize Food Choices: Choose lean meats, fish, and plant-based protein sources like legumes more frequently. Opt for low-fat or fat-free dairy products.
Read Nutrition Labels: Become adept at reading food labels. Look for 'partially hydrogenated oil' on the ingredients list and choose products with zero grams of trans fat. Also, check the saturated fat content and select products with lower percentages.
Cook at Home: Home cooking gives you complete control over the types and amounts of fats you use. Use healthy oils like extra virgin olive oil or canola oil for sautéing.
Limit Processed Foods: Packaged cookies, crackers, fried foods, and baked goods are common sources of both trans and saturated fats. Reducing your consumption of these items is one of the most effective strategies.

Conclusion: A Balanced Approach to Fats

Not all fatty acids are bad. The key to a healthy diet is distinguishing between the different types of fats and moderating your intake of the unhealthy ones, while incorporating more of the beneficial ones. Industrial trans fats should be avoided completely due to their profoundly negative effects on cardiovascular health, while saturated fats should be limited, not eliminated. By focusing on a balanced dietary pattern rich in unsaturated fats from sources like nuts, seeds, fish, and plant-based oils, you can significantly improve your overall health and reduce your risk of chronic disease. Making small, consistent changes to your eating habits can lead to substantial long-term benefits.

For more detailed dietary guidance and resources, consult the Dietary Guidelines for Americans.

Frequently Asked Questions

The main difference lies in their chemical structure. Saturated fatty acids have no double bonds and are typically solid at room temperature, while unsaturated fatty acids contain one or more double bonds, giving them a bent shape that keeps them liquid at room temperature.

Trans fats are the most unhealthy because they have a unique dual negative effect on cholesterol: they increase harmful LDL cholesterol while decreasing beneficial HDL cholesterol, which significantly raises the risk of heart disease.

There are small amounts of naturally occurring trans fats in meat and dairy from ruminant animals, but industrially produced trans fats from partially hydrogenated oils should be avoided entirely as they have no known health benefits and are harmful to cardiovascular health.

Common sources of saturated fat include fatty cuts of red meat, full-fat dairy products like butter and cheese, poultry skin, and tropical oils such as coconut and palm oil.

You can reduce saturated fat by making smart substitutions, such as choosing leaner cuts of meat, opting for low-fat dairy, and cooking with healthier liquid vegetable oils instead of solid fats like butter.

While it's a plant-based oil, coconut oil is high in saturated fat and should be consumed in moderation. It is best to prioritize sources of healthy unsaturated fats like olive oil in your diet.

Health guidelines recommend limiting saturated fat to less than 10% of your daily calories. The American Heart Association suggests an even lower target of under 6% for optimal cardiovascular health.