What two fats should you avoid? A Guide to Unhealthy Dietary Fats

October 7, 2025 •

5 min read

According to the World Health Organization, limiting saturated fats and eliminating industrially-produced trans fats from your diet is crucial for reducing the risk of heart disease. In the vast landscape of nutrition, understanding what two fats should you avoid can be the most impactful step toward better health. This article explores why trans fats and saturated fats pose significant health risks and how to reduce their intake effectively.

Quick Summary

This nutritional guide explains why trans fats and saturated fats should be limited or avoided for optimal heart health. It details the negative effects of these fats on cholesterol levels and provides practical advice on identifying their sources in processed foods and animal products. The guide also highlights healthier alternatives to incorporate into your diet for improved well-being.

Key Points

Avoid Trans Fats Completely: Industrially-produced trans fats from partially hydrogenated oils are the most dangerous fats and offer no nutritional benefit, so they should be eliminated from your diet.
Limit Saturated Fats: While not as harmful as trans fats, excessive intake of saturated fats from animal products and tropical oils can raise 'bad' LDL cholesterol and increase heart disease risk.
Check Labels for Partially Hydrogenated Oil: Always read ingredient lists to identify and avoid products containing partially hydrogenated oil, even if the nutrition label lists '0g trans fat' per serving.
Replace with Unsaturated Fats: Swap unhealthy saturated and trans fats with beneficial monounsaturated and polyunsaturated fats found in sources like avocados, nuts, seeds, and healthy oils.
Choose Lean Protein and Low-Fat Dairy: Opt for lean cuts of meat, skinless poultry, and low-fat dairy products to reduce your daily intake of saturated fat.
Prioritize Whole, Unprocessed Foods: A diet rich in whole foods, like vegetables, fruits, and whole grains, naturally limits your exposure to unhealthy processed fats and promotes better health.

Understanding the 'Bad' Fats: Trans and Saturated

While fat is a necessary component of a balanced diet, not all fats are created equal. The two types of fats that have been identified as potentially harmful to health are trans fats and saturated fats. Both can negatively impact your cholesterol levels, but they differ in their origin, chemical structure, and overall effect on the body. Making informed choices means understanding these differences and knowing how to spot them on food labels.

The Dangers of Trans Fats

Trans fats, particularly artificially produced ones, are widely considered the most dangerous type of fat for your health. They are created through a process called hydrogenation, where liquid vegetable oils are treated with hydrogen to make them solid or semi-solid at room temperature. This process is convenient for food manufacturers because it improves shelf life and texture, but it has severe consequences for human health.

Impact on Cholesterol: Trans fats uniquely harm your cholesterol profile by increasing LDL ('bad') cholesterol and simultaneously decreasing HDL ('good') cholesterol. This dual negative effect significantly raises your risk of developing heart disease and stroke.
Inflammation: Trans fats are also known to trigger systemic inflammation, which is a major factor in the development of chronic diseases like heart disease, diabetes, and stroke.
Insulin Resistance: Studies have linked trans fat intake to an increased risk of developing insulin resistance, a precursor to type 2 diabetes.
Sources: Common sources include partially hydrogenated oils found in many processed and fried foods, such as crackers, baked goods, pre-made dough, margarine, and fast food. Due to the severe health risks, many countries and health organizations, like the U.S. FDA, have banned or restricted the use of artificial trans fats.

The Problems with Saturated Fats

Unlike trans fats, saturated fats can occur naturally in many foods, primarily from animal sources. While your body needs some fat, and not all saturated fat has the same effect, excessive consumption is linked to health problems.

Impact on Cholesterol: The primary concern with high saturated fat intake is its ability to raise LDL ('bad') cholesterol levels. High LDL cholesterol contributes to the buildup of plaque in your arteries, increasing the risk of heart disease and stroke.
Calories and Weight Gain: Saturated fats are calorie-dense. Overconsumption can easily lead to weight gain, which is a risk factor for various health issues.
Sources: Saturated fats are found in high-fat meats (beef, pork), poultry skin, full-fat dairy products (butter, cheese, cream), and tropical oils (coconut and palm oils).

Comparison of Unhealthy Fats


Feature	Trans Fats (Artificial)	Saturated Fats
Origin	Created artificially via hydrogenation of liquid vegetable oils.	Found naturally in animal products and some plant-based oils.
Physical State	Solid or semi-solid at room temperature (e.g., shortening).	Typically solid at room temperature (e.g., butter, lard).
Cholesterol Impact	Worst effect: Increases LDL and decreases HDL cholesterol.	Negative effect: Increases LDL cholesterol.
Inflammation	Directly promotes inflammation.	Less direct link, but associated with overall unhealthy diet patterns.
Health Consensus	Strong medical consensus to avoid completely due to no nutritional benefits.	Consensus is to limit intake, with some controversy over its severity.
Common Sources	Processed baked goods, fried fast food, margarine.	Fatty meat, high-fat dairy, coconut oil.

How to Reduce and Replace Unhealthy Fats

Reducing your intake of trans and saturated fats is a major step toward improving your nutrition. The goal is not to eliminate fat entirely but to make smarter choices.

Strategies for Avoiding Trans Fats

Read Ingredient Labels: The most effective way to avoid trans fats is to check for "partially hydrogenated oil" on ingredient lists. Even if a product claims to have "0g trans fat," it can still contain small amounts if made with partially hydrogenated oils.
Limit Processed and Fried Foods: Reduce your consumption of commercial baked goods, fried fast food, and packaged snacks. These are common culprits for hidden trans fats.
Choose Healthier Cooking Oils: Opt for natural, unhydrogenated oils like olive, canola, and sunflower oil for cooking instead of shortening or stick margarine.

Strategies for Limiting Saturated Fats

Choose Leaner Meats: Trim visible fat from meat and opt for leaner cuts of beef and pork. Skinless poultry is also a better choice.
Opt for Low-Fat Dairy: Select low-fat or fat-free dairy products like milk, cheese, and yogurt to significantly reduce saturated fat intake.
Use Healthy Oils in Cooking: Replace butter, lard, and coconut oil with heart-healthy unsaturated oils.
Embrace Plant-Based Alternatives: Consider incorporating more plant-based protein sources like beans, lentils, and nuts, which are free of saturated fat and rich in beneficial nutrients.

Embracing Healthy Unsaturated Fats

Replacing unhealthy fats with unsaturated fats can further boost your heart health. These beneficial fats can lower LDL cholesterol and increase HDL cholesterol.

Excellent sources of unsaturated fats include:

Monounsaturated Fats: Found in avocados, olives, and olive, peanut, and canola oils.
Polyunsaturated Fats: Include omega-3s and omega-6s, found in fatty fish (salmon, mackerel), walnuts, flaxseeds, and sunflower, soybean, and canola oils.

For more detailed information on healthy fats, you can consult resources like the Harvard T.H. Chan School of Public Health's nutrition source.

Conclusion: Making Informed Dietary Choices

To summarize, the two fats to avoid or severely limit are industrially-produced trans fats and excessive saturated fats. While fat is a critical part of our diet, prioritizing healthy, unsaturated fats and making mindful choices about processed and animal-based products can have a profound impact on long-term health, particularly in reducing the risk of heart disease. By reading labels, being aware of common sources, and making simple substitutions, you can significantly improve your nutritional intake and overall well-being.

The Role of a Balanced Diet

It's important to remember that focusing on fat intake is just one aspect of a healthy diet. A balanced diet rich in vegetables, fruits, whole grains, and lean proteins is key to maintaining overall health. Combining a smart approach to fats with a diverse, nutrient-dense diet is the most effective strategy for preventing chronic disease and promoting a vibrant, healthy life.

The Evolving Science of Nutrition

Finally, it's worth noting that nutritional science is constantly evolving. While the harmful effects of trans fats are universally accepted, the recommendations for saturated fats have seen some nuance over time. The current consensus remains to limit saturated fat and replace it with healthier unsaturated fats. This highlights the importance of staying informed and basing dietary decisions on the latest evidence-based guidelines from reputable health organizations.

Frequently Asked Questions

Saturated fats are naturally occurring in animal products, whereas artificial trans fats are industrially created from liquid vegetable oils through a process called hydrogenation.

Trans fats are worse because they have a dual negative effect on cholesterol, increasing 'bad' LDL cholesterol while also decreasing 'good' HDL cholesterol, and they promote systemic inflammation.

Artificial trans fats are commonly found in processed foods, including baked goods, fried fast food, margarine, and snack foods made with partially hydrogenated oils.

You can identify artificial trans fats by looking for "partially hydrogenated oil" in the ingredients list, even if the nutrition facts state 0g trans fat per serving.

High-fat animal products like red meat, butter, cheese, and poultry skin contain high levels of saturated fat, as do some tropical oils like coconut and palm oil.

Healthier alternatives include monounsaturated and polyunsaturated fats found in olive oil, canola oil, nuts, seeds, avocados, and fatty fish.

While it's possible to avoid artificial trans fats by limiting processed foods and reading labels, small amounts of natural trans fats may exist in meat and dairy products from ruminant animals.