Nutrition Diet: Which fats are harmful for health?

October 22, 2025 •

3 min read

The World Health Organization (WHO) attributes over 278,000 deaths each year globally to the intake of industrially produced trans fats alone, underscoring the critical importance of understanding which fats are harmful for health. The two primary types of fat that should be limited or avoided for optimal health are trans fats and saturated fats.

Quick Summary

This article outlines the detrimental effects of trans fats and saturated fats on health. It details which foods contain these unhealthy fats, explains how to read food labels to identify hidden sources, and provides actionable steps to reduce their intake for better cardiovascular health.

Key Points

Avoid industrially produced trans fats: Found in partially hydrogenated oils used in many processed and fried foods, these are the most damaging fats for heart health.
Limit saturated fats: High intake of saturated fats, found in fatty meats, high-fat dairy, and tropical oils, can raise harmful LDL cholesterol.
Read ingredient lists: Always check for "partially hydrogenated oil" to spot trans fats, as labels can misleadingly claim "0g trans fat" per serving.
Swap unhealthy fats for healthy ones: Replace saturated and trans fats with unsaturated fats from sources like olive oil, avocado, and nuts to benefit heart health.
Choose healthier cooking methods: Opt for baking, grilling, and steaming over frying to reduce your consumption of added unhealthy fats.
Focus on whole foods: Prioritize a diet rich in fruits, vegetables, and whole grains, which are naturally low in unhealthy fats and higher in nutrients.

The Two Most Harmful Fat Types: Trans Fats and Saturated Fats

While some fats are essential for proper bodily function, providing energy and helping absorb key vitamins, others pose significant health risks. The two types that nutrition experts recommend limiting or avoiding are trans fats and saturated fats, both of which are linked to an increased risk of heart disease and other chronic conditions.

Trans Fats: The Most Detrimental Fat

Trans fats are considered the worst type of fat for your health. They exist naturally in small amounts in some meat and dairy, but the more concerning type is industrially produced through partial hydrogenation of vegetable oils. These industrial trans fats have no health benefits and negatively impact cholesterol by raising LDL and lowering HDL levels. High intake is linked to increased risk of heart disease, stroke, and type 2 diabetes.

Saturated Fats: A Need for Moderation

Saturated fats are typically solid at room temperature and found in animal products and some plant oils. While not needing complete elimination, excessive intake of saturated fat can raise LDL cholesterol, contributing to artery plaque buildup. Many health organizations advise limiting saturated fat to less than 6% of daily calories. The source of saturated fat is also important, as some foods containing it offer other beneficial nutrients.

Sources of Harmful Fats

Identifying sources of unhealthy fats helps in reducing intake. These fats are common in processed foods where they enhance texture and flavor.

Common sources of industrially produced trans fats:

Fried foods (e.g., french fries, doughnuts)
Baked goods (e.g., cookies, pastries)
Packaged snacks
Stick margarine and shortening
Frozen and ready-to-heat foods

Common sources of saturated fats:

Fatty meats and poultry skin
High-fat dairy (butter, cheese, whole milk)
Processed meats
Tropical oils (palm, coconut)
Many commercially prepared baked and fried items

How to Spot Unhealthy Fats on Food Labels

Food labels require careful reading, especially for trans fats. Labels can state "0 grams trans fat" if a serving has less than 0.5 grams. To avoid them, always check the ingredient list for “partially hydrogenated oil”, which indicates the presence of trans fats. For saturated fat, check the Nutrition Facts label and aim for products with lower percentages, considering your serving size.

Saturated vs. Unsaturated Fats: A Comparison


Feature	Saturated Fats	Trans Fats	Unsaturated Fats (Monounsaturated & Polyunsaturated)
State at Room Temp	Solid	Solid (industrial)	Liquid
Chemical Structure	No double bonds	Contains at least one double bond in the trans configuration	One or more double bonds in the cis configuration
Effect on Cholesterol	Raises LDL (“bad”) cholesterol	Raises LDL and lowers HDL (“good”) cholesterol	Lowers LDL and increases HDL cholesterol
Health Impact	Associated with increased risk of heart disease when consumed in excess	Strong link to heart disease, stroke, and diabetes; considered most harmful	Can reduce the risk of heart disease and inflammation; considered beneficial
Main Sources	Animal products (meat, dairy) and some tropical oils	Fried foods, baked goods, processed snacks containing partially hydrogenated oils	Plant oils (olive, sunflower), avocados, nuts, seeds, and fatty fish

Healthier Alternatives and Dietary Changes

Reducing harmful fat intake involves replacing them with healthier options rather than eliminating fat entirely.

Choose leaner meats and low-fat dairy.
Cook using methods like baking, grilling, or steaming instead of frying.
Replace solid fats with liquid vegetable oils like olive or canola oil.
Limit processed foods, commercial baked goods, and fried fast foods.
Incorporate foods rich in monounsaturated and polyunsaturated fats, such as avocados, nuts, and fatty fish.

Conclusion: Prioritizing Your Heart Health

Understanding which fats are harmful and making informed dietary choices is vital for cardiovascular health. Eliminating industrially produced trans fats and moderating saturated fat intake, replacing them with unsaturated fats, are key steps. Reading food labels and choosing whole foods are important for a heart-healthy diet. Transitioning to healthier fats supports a longer, healthier life. For global guidance on eliminating trans fats, consult organizations like the WHO.

Additional Tips for Managing Fat Intake

Be mindful of portion sizes, as all fats are calorie-dense.
Focus on whole grains, fruits, and vegetables.
Choose healthier snacks like nuts or fruit.
Inquire about cooking methods when dining out.

Frequently Asked Questions

Saturated fats are typically found in animal products and tropical oils and are solid at room temperature. Trans fats, particularly the harmful industrial kind, are created by hydrogenating liquid vegetable oils and are also solid, but have a much more damaging effect on cholesterol levels.

Trans fats are harmful because they raise your LDL ('bad') cholesterol and lower your HDL ('good') cholesterol, a combination that significantly increases your risk for heart disease, stroke, and type 2 diabetes.

To find hidden trans fats, check the ingredient list for 'partially hydrogenated oil,' as food labels can claim '0 grams trans fat' if the amount is less than 0.5 grams per serving.

While excessive intake of saturated fat is generally discouraged, recent research suggests that the food source matters. Some foods containing saturated fat also have beneficial nutrients. Still, replacing saturated fat with unsaturated fat is recommended for heart health.

Foods high in saturated fat include fatty cuts of red meat, processed meats like sausages and bacon, high-fat dairy products such as butter and cheese, and tropical oils like coconut and palm oil.

Healthier alternatives include monounsaturated and polyunsaturated fats found in foods like olive oil, avocados, nuts, seeds, and fatty fish. These can help improve cholesterol levels and reduce the risk of heart disease.

Simply following a low-fat diet is not the goal; the focus should be on replacing harmful fats with healthy ones. Eliminating all fats can lead to poor nutrient absorption, so prioritize unsaturated fats while limiting saturated and avoiding trans fats.