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The prevalence of obesity and Type 2 diabetes in America today is greater than ever before. Scientists believe that the type of fat we’re eating is putting us at greater risk for these illnesses.

In fact, a growing body of research shows that while the total amount of fat in your diet affects weight or disease, so does how much unhealthy versus healthy fat you consume.

This is because bad fats (trans fats and saturated fats) increase the risk for certain diseases and good fats (monounsaturated and polyunsaturated fats) do the opposite.

Fat and Cholesterol

Too much fat or cholesterol can lead to heart disease. But at appropriate levels, both can contribute to good health.

Almost all foods contain at least small amounts of fat, a nutrient. Fat provides us with an important source of energy and plays a vital role in how the cells in our body function.

Cholesterol is a wax-like substance that animals produce. Most cholesterol our body makes on its own, though some of it comes from the food we eat. 

Like fat, cholesterol helps to keep the body healthy. Cholesterol aids the body in making estrogen, testosterone, vitamin D, and other essential compounds.

Fat and cholesterol are insoluble and can’t dissolve in water or blood. The body produces protein particles (lipoproteins) to ferry cholesterol through the blood and triglycerides to carry fat.

  • Low-density lipoproteins (LDL): carry cholesterol from the liver to the rest of the body.
  • High-density lipoproteins (HDL): carry cholesterol to the liver and out of the body.
  • Triglycerides: transport fats in the bloodstream to cells throughout the body.

Good or Healthy Fats

When choosing what to eat, your best option is to choose unsaturated fats. These sorts of fats lower bad (LDL) cholesterol, increase good (HDL) cholesterol, and stabilize heart rhythms.

Good fats also ease inflammation — an overactivity of the immune system that research links to heart disease, stroke, diabetes, and other conditions.

High levels of HDL cholesterol seem to protect against heart attack. Low levels of HDL cholesterol increase the risk for heart disease.

Unsaturated fats include monounsaturated and polyunsaturated fats, which you can find mostly in nuts, plant-based oils, and fatty fish.

Good Fat Examples

Omega-3 fatty acids (these oils should be among your first choices)

Fatty, cold-water fish (salmon, mackerel, herring), flaxseeds, flax oil, and walnuts

Monounsaturated fat (these oils should be among your first choice)

Olive oil, peanut oil, canola oil, avocados, nuts, and seeds

Polyunsaturated fat (choose second)

Vegetable oils (safflower, corn, sunflower, soy, and cottonseed), nuts, and seeds

Bad or Unhealthy Fats

In the United States, saturated fats come primarily from eating meat, poultry skin, egg yolks, and whole-milk dairy products. You can also find saturated fat in tropical oils like coconut, coconut oil, palm oil, and palm kernel oil.  Tropical oils are often found as ingredients in processed foods and fast foods.

Your body makes all the saturated fat you need, so there is no reason to eat it. While it would be nearly impossible to eliminate all saturated fat from your diet, you should avoid it when you can.

Eating too much saturated fat can increase your risk of heart disease. Saturated fat increases total cholesterol and LDL cholesterol.

With too much LDL cholesterol in the blood, plaque forms in the walls of the arteries of the heart and other parts of the body. Plaque buildup in the arteries limits blood flow and, when it breaks apart, can cause a heart attack or stroke.

Trans Fats

Trans fatty acids, or trans fats, result from a manufacturing process in which liquid vegetable oil and hydrogen gas combine to make the oil a solid.

By partially hydrogenating vegetable oil, the oil becomes more stable and less likely to spoil. It also helps the oil withstand reheating without breaking down.

Most trans fats in the American diet come from margarines, snack foods, processed foods, commercially baked goods, and fried foods from restaurants.

Trans fats are worse for cholesterol levels than saturated fats because they raise bad LDL cholesterol, lower good HDL cholesterol, and increase inflammation. Trans fats, even in very small amounts, can be harmful to your health.

How Much Fat to Eat

We recommend aiming for these amounts of fats in your daily diet:

Unsaturated fats

Fat should make up about 30% of the calories you eat each day. Most of these should be from monounsaturated and polyunsaturated (especially Omega 3 Fatty Acid) sources. As general rule, choose unsaturated fats (usually in plant-based foods) over saturated fats (usually in animal-based foods or processed foods) as much as possible.

Saturated fats

Seven percent of total daily calories or lower. Keep your saturated fats as low as possible by limiting your intake of red meat, whole dairy products, egg yolks, fast foods, and highly processed foods. Think of animal products as side dishes, rather than main dishes.

Trans fats

No more than two grams a day. Even better, completely eliminate from your diet, if possible.