- Not all fats are created equal, the type of fat matters more than the total amount of fat in the diet.
- Unsaturated fats from olive oil, nuts, avocado, and oily fish, are associated with better cardiovascular outcomes and form the foundation of heart-healthy eating.
- Trans fats found mainly in heavily processed and fried foods, are the one type of fat the evidence consistently identifies as harmful and worth avoiding.
- Saturated fat is more nuanced than its reputation suggests, the source matters, and the overall dietary pattern matters more than any single food.
- The 2025–2030 US Dietary Guidelines retained the longstanding advice to limit saturated fat while placing new emphasis on avoiding highly processed foods and refined carbohydrates.
- Balance across all macronutrients, fat, protein, and carbohydrate, is the foundation of sustainable heart-healthy eating. No single nutrient is the villain.
Fat has had a difficult few decades in nutrition. From the 1970s onward, dietary fat, particularly saturated fat, was widely blamed for rising rates of heart disease, and “low fat” became synonymous with healthy eating. The result was a generation of low-fat products that often replaced fat with refined sugar and processed carbohydrates, which turned out to be far from ideal.
The science has moved on considerably since then. The picture is more nuanced, more interesting, and ultimately more encouraging, because it shifts the focus from a single nutrient to the overall quality and balance of what we eat. This article unpacks what we currently know about dietary fat, what the latest guidelines say, and what it means in practice for everyday food choices.
The Different Types of Dietary Fat
Fat is an essential macronutrient. It provides energy, supports cell function, helps absorb fat-soluble vitamins (A, D, E, and K), and plays a role in hormone production. The body cannot function without it. The question is not whether to eat fat, it’s which types, in what amounts, and as part of what overall dietary pattern.
There are four main types of dietary fat, and they behave quite differently in the body.
| Type of Fat | Main Sources | Effect on Heart Health |
|---|---|---|
| Monounsaturated fat | Olive oil, avocado, almonds, cashews | Associated with lower LDL cholesterol and reduced cardiovascular risk, consistently considered beneficial |
| Polyunsaturated fat | Oily fish, walnuts, flaxseed, sunflower oil | Includes omega-3 and omega-6 fatty acids, associated with reduced inflammation and cardiovascular protection |
| Saturated fat | Red meat, butter, full-fat dairy, coconut oil, palm oil | Associated with raised LDL cholesterol at high intakes, evidence is nuanced and source-dependent |
| Trans fat | Partially hydrogenated oils, fried fast food, some packaged baked goods | Raises LDL and lowers HDL cholesterol simultaneously, consistently associated with increased cardiovascular risk |
The Fats Most Associated with Heart Health Benefits
Monounsaturated Fats, The Mediterranean Cornerstone
Monounsaturated fats, found abundantly in extra-virgin olive oil avocado, and most nuts, are the fats most consistently associated with cardiovascular benefit in the research. They are the primary fat source in the Mediterranean diet, which has more large clinical trial evidence behind it than almost any other dietary pattern. Studies suggest they help lower LDL cholesterol while maintaining or raising HDL cholesterol, a favourable combination for heart health.
Extra-virgin olive oil in particular has been studied extensively. Beyond its monounsaturated fat content, it contains natural plant compounds called polyphenols with anti-inflammatory properties. For more detail, see our article on the heart benefits of olive oil.
Polyunsaturated Fats, Including the Omega-3s
Polyunsaturated fats include the omega-3 and omega-6 fatty acid families. Omega-3 fatty acids found in oily fish such as salmon, sardines, mackerel, and trout, as well as in walnuts and flaxseed, have been associated with reduced inflammation, lower triglycerides, and a reduced risk of cardiovascular events. They are one of the reasons oily fish features so prominently in heart-healthy dietary recommendations.
Omega-6 fatty acids found in vegetable oils such as sunflower and canola oil, also play an important role in health. The balance between omega-3 and omega-6 intake matters; modern Western diets tend to be much higher in omega-6 than omega-3, which is worth being aware of when thinking about overall fat composition. See our article on omega-3 and fish oil for more.
The Trans Fat Question, The One Clear Villain
If there is one area of near-universal agreement in nutrition science, it is on trans fats. Artificially produced trans fats, created through a process called partial hydrogenation that turns liquid vegetable oils into solid fats, raise LDL cholesterol and simultaneously lower HDL cholesterol. This is the worst possible combination from a cardiovascular perspective.
Trans fats have been progressively removed from the food supply in many countries following regulatory action, but they can still be found in some heavily processed foods, commercially fried products, and certain packaged baked goods. Checking ingredient labels for “partially hydrogenated oils” is a worthwhile habit, if it appears, trans fat is present regardless of what the nutrition panel says.
Saturated Fat, A More Nuanced Picture
Saturated fat is where the science is most genuinely complex, and where public messaging has been most inconsistent. The traditional view, that saturated fat raises LDL cholesterol and therefore drives heart disease, is broadly supported by evidence, but the picture has become more nuanced over time.
The source of saturated fat appears to matter. Saturated fat from whole food sources, full-fat dairy, for example, does not appear to carry the same cardiovascular risk as saturated fat from processed meats or heavily processed foods. The overall food matrix, not just the fat content in isolation, influences how the body responds.
What also matters significantly is what the saturated fat is replaced with. Replacing saturated fat with refined carbohydrates and sugar, as happened widely during the low-fat food era, does not improve cardiovascular outcomes. Replacing it with unsaturated fats from olive oil, nuts, and fish does. This distinction is critical and explains much of the confusion in the research literature over the past few decades.
The updated US Dietary Guidelines released in January 2026 attracted significant attention around dietary fat. The longstanding recommendation to limit saturated fat to less than 10% of total daily calories was retained unchanged. The American Heart Association continues to recommend an even lower threshold, under 6% of daily calories, for people managing cardiovascular risk.
What did change was a new emphasis on avoiding highly processed foods and refined carbohydrates a shift strongly supported by the evidence base. Some aspects of the new guidelines, particularly the visual emphasis on red meat, butter, and full-fat dairy, attracted criticism from independent nutrition scientists and the American Heart Association, who noted these elements sit in tension with the retained saturated fat limits.
The Bigger Picture, Fat in the Context of the Whole Diet
One of the most important shifts in nutritional thinking over recent decades is the move away from targeting individual nutrients and toward looking at overall dietary patterns. This is where the evidence is strongest and most consistent.
A heart-healthy diet is not simply a low-fat diet or a high-fat diet, it is a diet rich in whole, minimally processed foods that provides a good balance of all three macronutrients:
- Healthy fats from olive oil, avocado, nuts, seeds, and oily fish, provide essential fatty acids, support heart health, and help absorb fat-soluble vitamins. They are calorie-dense, so portion awareness matters, but they should not be avoided.
- Quality protein from fish, poultry, legumes, eggs, and smaller amounts of lean meat, supports muscle maintenance, satiety, and metabolic health. Maintaining adequate protein becomes increasingly important with age.
- Complex carbohydrates from whole grains, legumes, vegetables, and fruit, provide sustained energy, dietary fiber, and a wide range of micronutrients. They are digested more slowly than refined carbohydrates, supporting steadier blood sugar levels and longer-lasting energy.
Refined carbohydrates and added sugars, white bread, pastries, sugary drinks, packaged snacks, are increasingly recognised as a significant contributor to metabolic and cardiovascular risk. Reducing these, alongside moderating saturated fat and avoiding trans fats, is a consistent and well-supported approach to eating for heart health.
A Note on Calorie Density
Fat is the most calorie-dense macronutrient, providing roughly nine calories per gram, compared to four calories per gram from carbohydrate or protein. This doesn’t make fat unhealthy, but it does mean that foods very high in fat, even predominantly unsaturated fat, can contribute significantly to overall calorie intake. For people working toward weight management, being mindful of portion sizes of high-fat foods is worth considering alongside their quality.
A Note on High-Fat Diets Including Keto
High-fat, low-carbohydrate diets, including the ketogenic (keto) diet, have become widely popular and have genuine evidence supporting their use for weight loss and blood sugar management in some individuals. The cardiovascular implications of long-term high-fat diets depend considerably on the types of fat consumed. A keto diet built around olive oil, avocado, nuts, and oily fish sits in quite different cardiovascular territory to one built primarily around processed meats and saturated fat.
There is no single dietary approach that suits everyone. People following specific dietary plans, including keto, are encouraged to discuss their cardiovascular risk profile with their doctor, particularly if they have existing heart disease, elevated cholesterol, or other relevant conditions.
The question is never really “is fat good or bad?”, it’s “which fats, in what amounts, replacing what, as part of what overall pattern?” That’s a more complicated question, but it’s also a more honest one.
Putting It Into Practice
- Use extra-virgin olive oil as the primary cooking fat, it is the most evidence-supported fat source for cardiovascular health.
- Include oily fish regularly salmon, sardines, mackerel, and trout provide omega-3 fatty acids alongside high-quality protein. Twice a week is a commonly cited target.
- Eat a small handful of unsalted nuts most days walnuts, almonds, and cashews all provide a mix of healthy fats, protein, and fiber.
- Limit heavily processed and fried foods these are the most likely remaining sources of trans fats and tend to be high in refined carbohydrates and sodium too.
- Read ingredient labels for “partially hydrogenated oils” this indicates trans fat regardless of what the nutrition panel states.
- Think about the overall pattern rather than individual foods, a diet rich in vegetables, whole grains, legumes, fish, and healthy fats with limited processed foods is consistently associated with better cardiovascular outcomes.
Conclusion
The story of dietary fat is really the story of nutrition science growing up, moving from simple villains and heroes toward a more honest appreciation of complexity. Fat is not the enemy. Trans fats in processed foods warrant genuine caution. Saturated fat merits moderation and attention to source. And unsaturated fats, from olive oil, fish, nuts, and avocado, have a genuinely positive role to play in a heart-healthy diet.
More than any single fat type, what matters most is the overall quality and balance of what’s on the plate. A diet built around whole foods, with plenty of plants, good sources of protein, complex carbohydrates, and healthy fats, is the consistent thread running through the best dietary evidence we have. The Mediterranean diet remains one of the most practical and well-supported expressions of these principles in everyday eating.
As always, individual circumstances vary, and anyone with specific health concerns, particularly those managing existing heart disease, high cholesterol, or diabetes, is encouraged to discuss their dietary approach with their doctor or a registered dietitian.
