CHAPTER

4Fats: Essential Energy-Supplying Nutrients

Chapter 4 Outline

I. What Are Fats?

A. Fats are one form of a larger group of water-insoluble substances called lipids. In this chapter, we focus on three types of lipids found in food: triglycerides, phospholipids, and sterols.

B. Triglycerides can contain saturated or unsaturated fatty acid chains.

1. Triglycerides consist of three fatty acids attached to a glycerol backbone.

a. Fatty acids are long chains of carbon atoms bound to each other as well as to hydrogen.

b. Glycerol is an alcohol composed of three carbon atoms.

2. Saturated and unsaturated fats differ in hydrogen content.

a. Saturated fatty acids have no double bonds between carbons.

b. Monounsaturated fatty acids have one double bond in the carbon chain.

c. Polyunsaturated fatty acids have more than one double bond in the carbon chain.

3. Saturated and unsaturated fats differ in form.

a. Saturated fatty acids always form straight, rigid chains that pack tightly together.

i. Saturated fats are solid at room temperature.

b. Each double bond in unsaturated fatty acids gives them a kink, which makes them unable to pack together tightly.

i. Unsaturated fats are liquid at room temperature.

C. Trans fats are harmful to health.

1. Most trans fats are produced by hydrogenation.

D. Essential fatty acids protect our health.

1. Linoleic acid is an omega-6 fatty acid found in vegetable and nut oil.

2. Alpha-linolenic acid is an omega-3 fatty acid found primarily in leafy green vegetables, flax seeds, and soy, canola, and fish oils.

i. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are derivatives of alpha-linolenic acid found in fish oil.

E. Phospholipids combine lipids with phosphate.

1. Phospholipids are water soluble and consist of a glycerol backbone bound to two fatty acids with the addition of a phosphate compound.

F. Sterols have a multiple ring structure.

1. Cholesterol is the most common sterol in the diet.

Copyright © 2016 Pearson Education, Inc. 24

2. Our bodies synthesize cholesterol and it is also found in plant and animal foods.

II. Why Do We Need To Eat Fats?

A. Fats provide energy.

1. Fat provides 9 kilocalories per gram.

2. Fats are a major fuel source when we are at rest.

a. Fat provides 30 to 70 percent of the energy used by muscles and organs.

3. Fats fuel physical activity.

a. The longer you exercise, the more fat you use for energy.

B. Fats store energy for later use.

C. Fats enable the transport of fat-soluble vitamins.

D. Fats support body functions and structures.

1. Fats maintain integrity and flexibility of the cell membrane.

2. Fatty tissue pads the body and protects our organs.

E. Fats contribute to the flavor, texture, and satiety of foods.

III. What Happens To The Fats We Eat?

A. The mouth and stomach have limited roles in fat digestion.

B. The gallbladder, liver, and pancreas assist in fat breakdown.

1. The liver produces bile and sends it to the gallbladder for storage.

2. The gallbladder releases bile into the small intestine to help break up fat into small droplets.

3. Pancreatic enzymes break fatty acids away from their glycerol backbone.

a. Each triglyceride is broken down into two fatty acids and a monoglyceride.

C. Most fat is absorbed in the small intestine.

1. Micelles aid in fat absorption.

2. Lipoproteins transport fat in the bloodstream.

a. Chylomicrons transport dietary fat.

D. Fat is stored for later use.

1. Fat can be used immediately by cells for energy.

2. Fat can be used to make lipid-containing compounds in the body.

3. Fat can be taken up by the muscle or adipose tissue and stored for later use.

IV. How Much Fat Should We Eat?

A. The Acceptable Macronutrient Distribution Range (AMDR) for fat is 20 to 35 percent of total energy intake.

1. Intake of saturated and trans fatty acids should be minimized.

B. The Dietary Reference Intakes for specific fatty acids

1. The adequate intake for linoleic acid is 11 to 17 grams per day or 5% to 10% of en-ergy.

2. The adequate intake for alpha-linolenic acid is 1.1 to 1.6 grams per day or 0.6% to 1.2% of energy.

3. Saturated fat intake should be less than 7 percent of total energy intake.

4. Trans fat intake should be kept to an absolute minimum.

25 INSTRUCTOR MANUAL FOR NUTRITION FOR LIFE, 4/e Copyright © 2016 Pearson Education, Inc.

C. A shopper’s guide: choosing foods with healthful fats

1. Visible versus invisible fats

2. Food sources of beneficial fats

a. Eat more fish.

b. Choose plant-based foods.

c. Opt for low-fat food options.

V. What Role Do Fats Play In Chronic Disease?

A. Cardiovascular disease describes any condition involving dysfunction of the heart.

1. Coronary heart disease occurs when blood vessels supplying the heart become blocked or constricted.

2. Stroke is caused by blockage or rupture of one of the blood vessels supplying the brain.

3. Hypertension is a condition that increases risk for heart attack and stroke.

B. Dietary fats play an important role in cardiovascular disease.

1. Very-low-density lipoproteins (VLDLs) are made up mainly of triglyceride.

a. VLDLs will increase when a diet is high in saturated fat, simple sugars, and extra energy.

2. Diets high in saturated fat and trans fat increase low-density lipoprotein (LDL) levels in the blood.

a. High blood levels of LDL increase the risk of heart disease.

3. High-density lipoproteins (HDLs) remove cholesterol from the cardiovascular system.

a. High blood levels of HDLs are associated with a lower risk for coronary artery disease.

4. Total serum cholesterol is a ratio of the cholesterol made in the body versus that con-sumed in the diet.

a. High intakes of saturated and trans fatty acids can increase total serum cholesterol.

5. Trans fatty acids can raise blood LDL cholesterol.

C. Calculate your risk for cardiovascular disease.

1. Have simple blood tests performed to discover your lipid profile of LDL, HDL, and total serum cholesterol.

D. Reduce your risk for cardiovascular disease.

1. Maintain total fat intake to within 20 to 35 percent of energy and keep intake of satur-ated fats and trans fatty acids low.

2. Focus on including unsaturated fats from plat oils, nuts, and seeds in your diet.

3. Decrease your consumption of saturated fat to less than 7 percent of total energy in-take.

4. Increase your consumption of whole grains, fruits, and vegetables, so that total dietary fiber is 20 to 30 grams per day.

5. Schedule regular physical checkups.

6. Eat a healthful diet overall, restricting processed foods, sodium, and excess sugars.

7. Maintain an active lifestyle, exercising for 30 to 60 minutes most days of the week.

8. Maintain a healthy body weight.

9. Avoid using and being exposed to tobacco products.

Copyright © 2016 Pearson Education, Inc. CHAPTER 4 Fats: Essential Energy-Supplying Nutrients 26

D. Does a high-fat diet cause cancer?

1. Consuming a healthful diet and making healthy lifestyle choices will reduce the risk of some cancers. Conclusive evidence supports the impact of fat consumption on in-creased risk of colon cancer.

27 INSTRUCTOR MANUAL FOR NUTRITION FOR LIFE, 4/e Copyright © 2016 Pearson Education, Inc.