For years, many people have tried to avoid eating fat altogether, believing it’s always bad for health.
But the truth is, some fats are not only good for you—they’re essential.
According to Alice H. Lichtenstein, a senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, the key is understanding which fats help your body and which ones you should limit.
The fats we eat, known as lipids, are mostly in the form of triglycerides—three fatty acids attached to a molecule called glycerol.
During digestion, our bodies break triglycerides into individual fatty acids, which enter the bloodstream and are absorbed by cells for energy or to build important structures.
Fats are a crucial part of cell membranes, help produce certain hormones, and store energy for when we need it. They also help regulate body temperature and allow us to absorb vitamins A, D, E, and K.
Fats also make food taste better, adding flavor and texture.
But they are calorie-dense—providing nine calories per gram, compared with four for protein and carbohydrates.
This means it’s easier to consume more calories when eating high-fat foods, which can lead to weight gain if overall calorie intake is too high.
However, research shows that total fat intake alone doesn’t determine body weight—it’s the total calories from all sources that matter most.
One common misconception is that eating fat directly raises fat levels in the blood. In fact, diets very high in refined carbohydrates and low in fat are more likely to increase blood triglycerides.
That’s because the body can only store a small amount of excess carbohydrate, so the liver converts the rest into fatty acids and releases them into the blood as triglycerides.
Not all fats are the same. Fatty acids come in different shapes and lengths. Saturated fatty acids have no “gaps” in their carbon chains and tend to be solid at room temperature; they are found mainly in animal fats like meat and dairy.
Unsaturated fatty acids, which have one or more bends in their structure, are usually liquid at room temperature and are found in plant oils and fish.
There are two main types of unsaturated fats: monounsaturated (found in olive and canola oils) and polyunsaturated (found in soybean and corn oils). Some polyunsaturated fats, such as omega-3 and omega-6 fatty acids, are essential because our bodies can’t make them.
These are found in fish, nuts, seeds, and many plant oils. Diets rich in omega-3 fats from fish are consistently linked to lower heart disease risk.
Research shows that replacing saturated fats with unsaturated fats—particularly from nuts, seeds, plant oils, and fish—can reduce LDL (“bad”) cholesterol and lower cardiovascular risk. Claims that omega-6 fats increase inflammation have not been consistently supported in human studies.
The healthiest approach is not to cut out fat, but to choose sources that contain more unsaturated than saturated fats.
That means swapping butter, lard, coconut oil, and fatty meats for foods like olive oil, canola oil, soy products, fish, nuts, and seeds. By making these changes, you can enjoy the flavor and benefits of fat while supporting your long-term health.
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Source: Tufts University.
