Fats or lipids are other macronutrients necessary for the body. Having many life – saving functions in the body, fats are essential for humans.

Based on the presence or absence of double bonds, fats are classified into saturated and unsaturated groups. The unsaturated fats themselves are categorized into monounsaturated and polyunsaturated groups.

Double bonds based on which fats are classified are sets of carbons that store higher amounts of energy and are chemically very active. Saturated Fat (SF) is a fat that has no double bonds at all.

Monounsaturated Fat (MUSF) is a fat with only one double bond. Polyunsaturated Fat (PUSF) is a fat that has two or more double bonds in its structure.

Food Sources of Different Types of Fats:
Saturated	Monounsaturated	Polyunsaturated
Animal based: -       Beef -       Butter -       Chicken -       Dairy products -       Egg yolk -       Lamb -       Pork Plant based: -       Coconut oil -       Hydrogenated margarine -       Palm oil -       Vegetable shortenings	Almond oil Avocado Canola oil Cashews Olive oil Peanuts Pecans Pistachios	Omega – 3: -       Chia seeds -       Fish -       Flaxseeds -       Hemp seeds -       Pumpkin seeds -       Walnut Omega – 6: -       Black currant oil -       Borage oil -       Corn oil -       Evening primrose oil -       Grapeseed oil -       Poppyseed oil -       Safflower oil -       Sesame oil -       Soybean oil -       Sunflower oil -       Walnut oil -       Wheat germ oil

 

Most oils and food items contain a combination of all three types of fats with different percentages (see the table below).

 

Percentage of Different Fats in Different Oils and Food Items:
Oils or Food Items	Saturated Fat	Monounsaturated Fat	Polyunsaturated Fat
Almond butter	10	60	30
Avocado oil	10	75	15
Butter	65	30	5
Canola oil	5	60	35
Coconut oil	93	5	2
Corn oil	15	25	60
Cottonseed oil	25	20	55
Lard	40	50	10
Olive oil	15	75	10
Palm oil	50	40	10
Peanut oil	15	50	35
Pistachio oil	15	55	30
Safflower oil	10	10	80
Soybean oil	15	25	60
Sunflower oil	10	20	70
Tallow	54	45	1

 

How Much Fat Do We Need?

 

According to health authorities, the total daily intake of fats in an average person should be about 25% of total daily calories or 65 grams a day, whichever counts lower. For a better understanding, just take a look at the following examples:

Example 1:

Suppose your totally daily calories are 3000. Twenty five percent of your calories would be 750. Since 1 gram of fat generates 9 calories, 750 divided by 9 equals to 83. Your total daily fat intake should be 65 grams, because 65 is smaller than 83.

Example 2:

If your total daily calories are 1800, twenty five percent of it would be 450, which is equal to 50 grams of fat. Your total daily fat intake should be 50 grams, because 50 is smaller than 65.

Daily Needs of Fats:
Fat	Daily intake
Total fat	65 grams
Total saturated fat	20 grams
Cholesterol	300 milligrams

 

Functions of Fats in the Body (Why Do We Need Fats?):

 

Fats have many life supporting functions in the body:

1) They are a big part of cell membrane, keeping the cell stronger against invasion by microorganisms and damage by chemicals.

2) They have a key role in the nervous system.

3) They are important in the formation of sex hormones.

4) They play a crucial role in forming bile acids and vitamin D.

5) They are potential sources of energy by generating 9 calories per one gram.

6) They act as a protective blanket, shielding the internal organs from trauma and cold, especially the heart, kidneys, liver, spleen, and spinal cord. About 4% of the body`s fat is in the protective blanket.

7) Fat under the skin helps prevent from heat loss and protect the body against external temperature changes. In fact, the subcutaneous fat helps people tolerate extreme cold by acting a thermal insulation.

8) Fats facilitate absorption of vitamins A, D, E, and K.

9) Lipids are good hunger suppressors. After ingesting fats, it takes about 3 to 4 hours for the stomach to deliver them to the small intestine. In facts, lipids stay longer in the stomach, decreasing the release of hunger hormone, ghrelin, followed by a decrease in hunger feeling.

Cholesterol:

 

Cholesterol is the main sterol synthesized by the body. The total body content of cholesterol in an average person is about 35 grams, which is primarily incorporated in the cell membranes and a small amount is in the blood. The liver synthesizes approximately 70% of the body`s total cholesterol. Daily production of cholesterol in the body varies between 0.5 and 2 grams.

For different types of cholesterol (LDL and HDL), dietary changes and supplementations, see “High Cholesterol and Triglyceride” under the section of “Medicinal Nutrition”.

Phytosterols are cholesterol – like compounds found in plants (see “Phytosterols” under the section of “Phytonutrients”).

 

Food Sources of Cholesterol:
Foods	Serving Size	Cholesterol (mg)
Beef, cuts	100 grams	80
Cheese -Cottage cheese 1% -Cheddar cheese -Swiss cheese	100 grams 100 grams 100 grams	10 100 80
Chicken, roasted	100 grams	80
Egg yolk	One medium	210
Cream cheese	100 grams	110
Fish -Tuna, canned -Sardines, canned	100 grams 100 grams	50 140
Lamb -Cuts -Raw	100 grams 100 grams	80 370
Liver, chicken	100 grams	600
Milk -Skim -1% -2% -3.25% (Whole milk)	1 cup 1 cup 1 cup 1 cup	5 10 20 30
Pork -Cuts -Raw	100 grams 100 grams	80 370
Shrimp	100 grams	190
Turkey, roasted	100 grams	100
Yogurts	1 cup	10 – 30

 

Triglyceride:

 

Triglyceride (TG) constitutes approximately 95% of the fats in the body and foods. It is the stored form of fat and made of glycerol attached to three fatty acids. Glycerol is water – soluble and short chain carbohydrate.

For blood levels of TG, dietary changes and supplementations, see “High Cholesterol and Triglyceride” under the section of “Medicinal Nutrition”.

 

Rancidity:

 

When unsaturated fats are exposed to heat, oxygen and light, they convert to hydroperoxides which break down into volatile aldehydes, esters, alcohols, ketones, and hydrocarbons, giving unpleasant odour and flavour to foods. This chemical process is called “lipid peroxidation” or commonly known as “rancidity”.

In order to prevent from rancidity, antioxidants such as vitamin E, B- carotene, BHT or BHA are usually added to unsaturated fats.

Trans – Fats: 

Trans - fats are unsaturated fats in which double bonds have moved from cis-positions to the opposite side to trans-positions. Saturated fats never change to Trans – fats, because they do not contain any double bonds.Tran -fats are made by adding hydrogen to vegetable oils through a process called hydrogenation, which makes the oils less likely to spoil.

Using Trans - fats in manufacturing foods helps foods stay fresh longer, have a longer shelf life and have a less greasy taste.

Foods high in Trans-fats include vegetable shortenings, some margarines, crackers, cookies, cakes, doughnuts, muffins, pies, French fries, and deeply fried foods.

The problem with Trans – fats is that they increase LDL Cholesterol dramatically, placing the person at increased risk for heart disease.

Metabolism of Fat During Exercise:

 

See "Metabolism of Fat During Exercise" under the section of "Energy Map".