Good-Fats (Unsaturated) vs. Bad-Fats (Saturated)

Healthy or “Good” Fats (Unsaturated Fats)

Doctors consider monounsaturated fat and polyunsaturated fat more “heart-healthy” fats or good-fats. These are fats that are better choices for our diet.
Good-fats come mainly from vegetables, nuts, seeds, and fish. Foods that primarily contain these healthier fats tend to be liquid when they’re at room temperature. An example is vegetable oil. They can improve blood cholesterol levels, ease inflammation, stabilize heart rhythms, and play a number of other beneficial roles.
There are two broad categories of beneficial good-fats: monounsaturated and polyunsaturated fats. Monounsaturated fats and polyunsaturated fats are known as the “good fats” because they are good for our heart, our cholesterol, and our overall health. These fats can help us to:

• Lower the risk of heart disease and stroke.
• Lower bad LDL cholesterol levels, while increasing good HDL.
• Prevent abnormal heart rhythms.
• Lower triglycerides associated with heart disease and fight inflammation.
• Lower blood pressure.
• Prevent atherosclerosis (hardening and narrowing of the arteries).

Adding more of these healthy fats to our diet may also help to make we feel more satisfied after a meal, reducing hunger and thus promoting weight loss.

Monounsaturated Fat

This type of helpful fat is present in a variety of foods and oils. Research has consistently shown that eating foods that contain monounsaturated fat can improve our blood cholesterol level, which can decrease our risk of heart disease and may also help decrease the risk of type 2 diabetes. Eating foods that are high in monounsaturated fats may help lower our "bad" LDL cholesterol. Monounsaturated fats may also keep "good" HDL cholesterol levels high. But eating more unsaturated fat without cutting back on saturated fat may not lower our cholesterol.
The discovery that monounsaturated fat could be healthful came from the Seven Countries Study during the 1960s. It revealed that people in Greece and other parts of the Mediterranean region enjoyed a low rate of heart disease despite a high-fat diet. The main fat in their diet, though, was not the saturated animal fat common in countries with higher rates of heart disease. It was olive oil, which contains mainly monounsaturated fat. This finding produced a surge of interest in olive oil and the "Mediterranean diet," a style of eating regarded as a healthful choice today.

Good sources of Monounsaturated Fats include:     

• Olive, canola, peanut, and sesame oils
• Avocados
• Nuts (almonds, peanuts, macadamia, hazelnuts, pecans, cashews)
• Peanut butter and almond butter
• Seeds such as pumpkin and sesame seeds

Polyunsaturated Fat

Polyunsaturated fats are known as “essential fats” because the body cannot make them and needs them from foods.
Plant-based foods and oils are the primary source of this fat. When we pour liquid cooking oil into a pan, there's a good chance we're using polyunsaturated fat. Like monounsaturated fat, polyunsaturated fat can decrease your risk of heart disease by lowering blood cholesterol levels. This type of fat is found mostly in plant-based foods and oils. Evidence shows that eating foods rich in polyunsaturated fatty acids instead of saturated fats improves blood cholesterol levels, which can decrease our risk of heart disease and may also help decrease the risk of type 2 diabetes.
Eating polyunsaturated fats in place of saturated fats or highly refined carbohydrates reduces harmful LDL cholesterol and improves the cholesterol profile. It also lowers triglycerides.

Good sources of Polyunsatureted Fats include:

• Sunflower, sesame, and pumpkin seeds
• Flaxseed
• Walnuts
• Fatty fish (salmon, tuna, mackerel, herring, trout, sardines) and fish oil
• Soybean and safflower oil
• Soymilk
• Tofu

A certain type of this fat, called omega-3 fatty acids, have been shown to be particularly beneficial for our heart. Omega-3s appear to not only decrease the risk of coronary artery disease, but also help lower blood pressure levels and guard against irregular heartbeats. The following types of fatty fish contain omega-3 fatty acids:

• salmon
• herring
• sardines
• trout

We can also find omega-3s in flaxseed, walnuts, canola oil and unhydrogenated soybean oil, although these contain a less active form of the fat than fish do. Omega-3 fatty acids may help prevent and even treat heart disease and stroke. In addition to reducing blood pressure, raising HDL, and lowering triglycerides, polyunsaturated fats may help prevent lethal heart rhythms from arising. Evidence also suggests they may help reduce the need for corticosteroid medications in people with rheumatoid arthritis. Studies linking omega-3s to a wide range of other health improvements, including reducing risk of dementia, are inconclusive, and some of them have major flaws, according to a systematic review of the evidence by the Agency for Healthcare Research and Quality.
In addition to omega-3 fatty acids, we can find polyunsaturated fat in the following foods, which contain omega-6 fatty acids:

• tofu
• roasted soy beans and soy nut butter
• walnuts
• seeds (sunflower seeds, pumpkin seeds, sesame seeds)
• vegetable oils (corn oil, safflower oil, sesame oil, sunflower oil)
• soft margarine (liquid or tub)

Omega-6 fatty acids have also been linked to protection against heart disease.

Unhealthy or “bad” fats (Saturated Fats)

Two types of fats — saturated fat and trans fat — have been identified as potentially bad-fats harmful to our health. Most of the foods that contain these types of fats are solid at room temperature, such as:

• butter
• margarine
• shortening
• beef or pork fat

Trans fat should be avoided while saturated fats should be eaten very sparingly.

Saturated Fat

This type of fat comes mainly from animal sources of food, such as red meat, poultry and full-fat dairy products. Saturated fats raise high-density lipoprotein (HDL or "good") cholesterol and low-density lipoprotein (LDL or "bad") cholesterol levels, which may increase our risk of cardiovascular disease. Saturated fat can raise bad LDL cholesterol and too much can negatively impact heart health, so it’s best consumed in moderation. While there’s no need to cut out all saturated fat from our diet, most nutrition experts recommend limiting it to 10% of our daily calories.
Saturated fat is solid at room temperature, that is why it is also known as "solid fat." We'll find tropical oils in many snacks and in non-dairy foods, such as coffee creamers and whipped toppings. Foods made with butter, margarine, or shortening (cakes, cookies, and other desserts) have a lot of saturated fat.
The American Heart Association (AHA) recommend that people eat no more than 13 grams of saturated fat per day. 

Some sources of saturated fat include:

• animal meats and meat products
• dairy products, except those that are fat-free
• processed foods, including baked goods, snack foods, and french fries
• some vegetable oils, including coconut oil, palm oil, and cocoa butter

Research indicates that it is not healthful to replace saturated fat in the diet with refined carbohydrates or sugar, which are also bad for health. Instead, a person should replace sources of saturated fat with more healthful foods, such as nuts, seeds, avocados, beans, whole grains, and vegetables.

Primary sources of Saturated Fats include:

• Red meat (beef, lamb, pork)
• Chicken skin and poultry skin
• High-fat dairy foods (whole milk, butter, cheese, sour cream, ice cream)
• Butter
• Ice cream
• Lard
• Tropical oils (coconut oil, palm oil, cocoa butter)

A 2015 review of 15 randomized controlled trials looked at saturated fats and heart disease. The researchers concluded that replacing saturated fat in our diet with polyunsaturated fats can reduce our heart disease risk. While the risk reduction is low, these differences could make a difference to our health. A 2017 journal article in the British Journal of Sports Medicine reported that the risks of LDL cholesterol had previously been overstated, particularly when it comes to a negative effect on heart health.

Trans Fat

Trans fats are manufactured. This is a fat that has been changed by a process called hydrogenation. They are the product of a process that adds hydrogen to liquid vegetable oils to make them more solid. Another name for trans fats is partially hydrogenated oils.
This process increases the shelf life of fat and makes the fat harder at room temperature. Harder fat makes crispier crackers and flakier pie crusts. Partially hydrogenated oils can withstand repeated heating without breaking down, making them ideal for frying fast foods.
Trans fats are not essential, and they have damaging health effects.
Trans fats raise levels of LDL cholesterol and lower levels of HDL cholesterol. This increases the risk of heart disease, stroke, and type 2 diabetes.
The World Health Organization (WHO) estimate that trans fats are linked with 500,000 cardiovascular deaths each year. Trans fats became popular when food companies found them easy to use and cheap to produce. They also have a long shelf life and can give food a nice taste. As trans fats can be used in commercial fryers many times over, they have become common in fast-food chains and other restaurants. However, the WHO have called on governments to eliminate trans fats from the global food supply. Most commercial food production companies have now eliminated trans fats from their products.
Trans fats are the worst type of fat for the heart, blood vessels, and rest of the body because they:

• Raise bad LDL and lower good HDL
• Create inflammation – a reaction related to immunity – which has been implicated in heart disease, stroke, diabetes, and other chronic conditions
• Contribute to insulin resistance
• Can have harmful health effects even in small amounts – for each additional 2 percent of calories from trans fat consumed daily, the risk of coronary heart disease increases by 23 percent.

Primary sources of Trans Fats include:

• Commercially-baked pastries, cookies, doughnuts, muffins, cakes, pizza dough
• Packaged snack foods (crackers, microwave popcorn, chips)
• Stick margarine, vegetable shortening
• Fried foods (French fries, fried chicken, chicken nuggets, breaded fish)
• Anything containing hydrogenated or partially hydrogenated vegetable oil, even if it claims to be “trans fat-free”

The AHA advise that consumption of trans fats should not exceed 5–6% of a person’s total caloric intake. However, consuming any amount of these fats increases health risks.