Fat got a bad reputation for decades, and you might still feel the effects of that in how you eat. Every supermarket shelf is filled with low-fat products. People swapped butter for margarine and cut back on cooking oil almost to nothing. The science behind much of that advice turned out to be incomplete, and in some cases, just wrong.
Your body needs fat. Not just a little of it, but a meaningful amount every day. What matters most is which types you eat most often. Different fats do genuinely different things inside your body.
Key InsightNot all fats work the same way in your body. Healthy fats, like those found in olive oil, avocados, nuts, and oily fish, actively protect your heart, support your brain, and help keep inflammation in check. Saturated fats, mainly from animal products, are fine in moderate amounts but raise your LDL cholesterol if you eat too much. Trans fats, created by industrial hardening of oils, have no safe level and should be avoided entirely. Knowing the difference helps you make smarter choices every time you cook or shop. |
Why Your Body Can’t Function Without Fat
Fat serves several functions that nothing else in your diet can replace. Your body uses it to absorb the fat-soluble vitamins: A, D, E, and K. If you don’t eat enough fat, those vitamins pass straight through your system.
That happens even when your food is full of them. Fat also forms the outer layer of every cell in your body. It helps produce your hormones and acts as your longest-lasting fuel source. Fat has 9 calories per gram, more than the 4 you get from protein or carbs. That’s not a reason for you to avoid it. It’s a reason to choose the right kinds.
When you look at dietary fats, they’re all built from fatty acid chains. Whether a fat is solid or liquid in your kitchen depends on how those chains are structured. Saturated fats have no double bonds, which is why they’re solid when you take them out of the fridge.
Unsaturated fats have one or more double bonds, which keep them liquid at room temperature. Trans fats are in their own category. They’re made when liquid oils are industrially hardened, and your body doesn’t handle them well.
The Healthy Fats Worth Adding to Your Diet
Healthy fats, particularly monounsaturated fats, are the type most strongly linked to heart protection.
Your best everyday source is olive oil. You’ll also find them in avocados, almonds, cashews, and peanut butter.
These fats raise your HDL cholesterol, which clears your arteries, and lower your LDL, which builds up in them. Replacing saturated fat with monounsaturated fat in your regular cooking makes a real difference to your heart health over time. You won’t feel it after one meal, but the pattern builds in your body across months and years.
Polyunsaturated fats include omega-3 and omega-6 fatty acids, neither of which your body can make on its own. That means you have to get them from food.
Omega-3s are your most valuable target here. You find them in fatty fish like salmon, mackerel, and sardines. You also get them from walnuts, chia seeds, and ground flaxseeds. Omega-3s reduce your inflammation, support your brain as you age, and help protect your heart.
In your kitchen, omega-6s show up in sunflower oil and most processed snacks. They do have a role in your body, but most people already eat far too much omega-6 relative to omega-3. That imbalance tends to push your body towards more, rather than less, inflammation.
Your practical fix isn’t to cut omega-6s obsessively. It’s to add more omega-3-rich foods to your week. Fatty fish twice a week will shift your balance. So will a handful of walnuts in the afternoon, or some ground flaxseed in your morning bowl.
The Fats to Eat Less of, and the One to Avoid Entirely
Saturated fat is the type that needs some moderation from you. Your body does use it, and you don’t need to cut it out entirely. But eating large amounts regularly raises your LDL cholesterol, which can contribute to plaque buildup in your arteries over time.
Your main saturated fat sources are butter, cheese, full-fat dairy, fatty cuts of red meat, and chicken skin. If you use palm oil or coconut oil regularly in your cooking, both are high in saturated fat. That’s worth keeping in mind.
The general guidance is to keep your saturated fat intake to around 5 to 6 percent of your daily calories. On a typical 2,000-calorie diet, that works out to roughly 11-13 grams per day. Think of it as about one tablespoon of butter in your day. You don’t have to count every gram. Just avoid making high-saturated-fat foods your everyday staples, and you’ll stay in a reasonable range.
Trans fats are the one category your body has no good use for at all. Artificial trans fats raise your LDL cholesterol while simultaneously lowering your HDL. That double effect is particularly damaging to your heart.
They also increase your inflammation and raise your risk of type 2 diabetes. Trans fats once appeared regularly in foods you’d eat every day: margarine, packaged biscuits, and fried fast food.
In the UK and many other countries, they’ve now been largely removed from the food supply. But they can still appear in some imported or heavily processed products you buy. If you see “partially hydrogenated oils” on an ingredients list, that’s a trans fat. Choosing something else is worth your time.
Simple Swaps That Make a Real Difference
You don’t need to track fat percentages at every meal. A few practical habits will take you a long way.
- Use olive oil as your default cooking fat, rather than butter or lard.
- Keep a jar of nut butter in your kitchen and reach for it when you want something quick.
- Add fatty fish to your week twice, whether that’s fresh salmon, tinned mackerel, or sardines on toast.
- Swap your afternoon biscuits for a small handful of walnuts or almonds.
- Check the label on any packaged cooking oil or spread you buy regularly. If it lists hydrogenated oils, swap it for something else.
When you eat foods that are naturally higher in saturated fat, enjoy them as part of a full meal. A modest portion of cheese alongside your vegetables is nutritionally quite different from making it your main event every day.
Getting the Balance Right for Your Long-Term Health
The short version of all this: your body needs healthy fats to function well. Your body works better with some types of fat than others. Your best everyday choices are unsaturated fats from olive oil, avocados, nuts, seeds, and oily fish. Your saturated fat intake is fine in modest amounts. Trans fats are best avoided in your diet.
Getting that balance broadly right, most of the time, is what protects your health over the long run. You don’t need to be perfect. You just need a reliable pattern that works for your life.
