ISSA Nutritionist Chapter 6: Fats

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Chapter Goals:

• Know the roles that lipids play in the body.
• Find the different types of fats and their primary functions.
• Be able to explain the differences that exist between essential and nonessential lipids.
• Be able to explain how the body digests fats.
• Fin the nutritional sources of fats.

Introduction

Fats are also called lipids, and these macronutrients have long been demonized in the health and nutrition realms. 

However, this macronutrient plays a vital role in human physiology and is just as important as proteins and carbs. 

Fat molecules are dense and yield high levels of energy through beta-oxidation. 

Lipids are necessary as part of a balanced diet for these main reasons:

• They are stored and needed for the use of fat-soluble vitamins like A, D, E, and K.
• They keep the function and integrity of the cell membranes.
• They provide a concentrated source of energy.
• They make our meals more palatable and filling to eat.

Fats

The major lipids found in the body are:

• Triglycerides
• Fatty acids
• Essential fatty acids
• Omega-3 fatty acids
• Gamma-linolenic acid
• Medium chain triglycerides
• Phospholipids
• Lecithin
• Cholesterol

The building blocks of the lipids are fatty acids and the small molecule glycerol. Fatty acids are long chains of hydrogen and carbon, ranging from 4 – 36 total carbons. 

We classify fatty acids by carbon chains as such:

Short-chain fatty acids will have 4 – 5 carbon atoms

Medium-chain fatty acids will have 6 – 12 carbon atoms

Long-chain fatty acids will have 19 – 23 carbon atoms

Anything with 20 or more carbon atoms is a long-chain fatty acid

Three fatty acids linked to a molecule of glycerol form a triglyceride. 

Nutritional fats will be separated into two types: saturated and unsaturated. 

Unsaturated fats are fats with one or more double bonds between the carbon atoms in the fatty acid chains. We can further divide them into monounsaturated and polyunsaturated fatty acids. 

Saturated fats have the max number of hydrogen atoms. There are no carbon double bonds.

The Roles of Lipids in the Body

Fats have a long-standing reputation in the realm of health and fitness, and this has been both positive and negative.

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The main functions of fats in the body are:

• A major source of fuel in exercise
• Stores of body fat are used for insulation and regulation of temperature
• Absorption and storage of fat-soluble vitamins
• Storage for energy
• A supply of essential fatty acids unable to be provided by the body
• Protection in the form of padding for body structures and other structures in the body
• Structures in membranes and other cell structures
• Healthy skin
• The building blocks for other biomolecules
• Hormone synthesis

When the cellular energy needs of the body have been met, excess energy will be stored as body fat, also known as adipose tissue. 

Lipogenesis usually happens in conditions of higher energy and insulin levels. Lipolysis reverses the process when both energy availability and insulin levels are low, and stored fat will then be metabolized for energy.

Fats have a vital role in producing hormones, and nutritional intake of fats can affect several hormones and their downstream effects. 

Essential Fatty Acids

Of the many lipids, only two of them are actually going to be essential. The rest are important, but they are not essential for us. 

Essential fatty acids cannot be manufactured in the body, as we discussed with the Essential Amino Acids. 

Some specific functioning of the essential fatty acids are:

• Maintenance of the structure and function of cellular and subcellular membranes. 
• Serving as precursors for the eicosanoids
• Transfer of oxygen from the lungs to the alveolar membrane
• Maintaining proper brain and nervous system function
• Production of prostaglandins 
• Formation of healthy skin and hair
• The healing and repair of wounds and as an inflammatory response

Omega-3 and Omega-6

The omegas are named after their chemical structure and the location of their final double bond. 

The omega 3 fatty acids are essential for our diets and play a vital role in the human cell membrane on a micro level.

Omega 6 fatty acids are the other essential fatty acids, and they are used for energy in the body. 

Linoleic Acid

This helps to reduce the deposits of adipose tissue and improve the function of our immune systems.

Excess levels can cause headaches, inflammation, and lethargy.

Alpha-Linolenic Acid

This is an omega-3 fatty acid and a polyunsaturated fat found in animal and plant oils. 

EPA and DHA

These are omega 3 fatty acids, but they can be produced from ALA, making them conditionally essential.

These are important in cardiovascular disease risks. 

Gamma Linolenic Acid

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This is another important fatty acid from linolenic acid that can be manufactured within the body.

Nonessential Fatty Acids

Omega 9 

These are nonessential and they are monounsaturated, so they only have one bond. They have significant metabolic benefits. 

Phospholipids

These differ from triglycerides because they have two fatty acid groups and one phosphate group attached to a glycerol molecule.

They serve as a major structural component for cells due to their presence in the cell membranes. 

We have several types of phospholipids, with lecithin being the most focused on in supplements. 

Cholesterol

This fat is a member of lipids known as sterols, and it is produced in the body.

Nutritional cholesterol comes mostly from animal products, although plants provide some small amounts of it. 

This cell is a major component of cells, a precursor for bile acids, and plays a role in the sex hormones and adrenal hormones. 

We have two types of cholesterol, LDL and HDL. 

HDL is considered to be the healthy cholesterol, while LDL is considered to be the unhealthy form of cholesterol.

Conjugated Linolenic Acid

This is an isomer of linoleic acid, and it is sometimes called rumenic acid.

Conjugated means that it is formed through the union of two molecules with two double bonds separated by one single bond. 

Medium Chain triglycerides

These were originally made as a source of calories for people with problems digesting longer chain fatty acids. 

These fatty acids dissolve more easily in water and can pass directly to the bloodstream from the intestines.

Trans Fatty Acids

These are also called trans fats, and they naturally occur in small levels in some animal products. They are produced synthetically by hydrogenating vegetable oils. 

Food makers will hydrogenate the unsaturated vegetable oils to preserve them.

Digestion of Fats

This is a much more detailed process than the other macronutrients. Each segment of the Digestive tract will play a different role in packaging, absorbing, transporting, and storing fats within the body. 

From the mouth to the stomach

Like the other molecules, fats will begin to break down in the mouth through chewing.

We have an enzyme known as lingual lipase that starts to digest fats through saliva and some amino acids to break the bonds down. 

In the stomach, gastric lipase will be used to break the triglycerides into diglycerides and fatty acids. 

The stomach churning helps to add to the breakdown also. This whole process takes much longer than carbs, and in 2-4 hours, we will still only have 30% of the fats broken down. 

Absorption to the Bloodstream

We have four pathways by which fatty acids will enter the bloodstream: the exogenous pathway, endogenous, reverse cholesterol transport, and ketogenesis.

Nutritional Sources of Fats

When we are choosing the foods to eat based on saturated and unsaturated fats, it is rather important to strike a balance. 

Plant foods are rich in unsaturated fats; the opposite is true for animal fats. 

While animal foods may provide less healthy fat, they have the high-quality proteins needed. So, it really is a tradeoff. 

When eating fat-rich foods, it is important to focus on the following:

• Olives and olive oil
• Avocados
• Nuts
• Seeds

Some fats to avoid would be:

• Butter
• Bacon
• Cream
• Mayo
• Faull-fat dairy products
• Deep-fried foods

Recommended Dietary Allowances

In a normal average American diet, fat will take up around 45% of the calories, which is far too much. 

The AHA recommends keeping the amount around 30-35% and then closer to 20% if we are trying to lose or maintain weight. 

But it is also recommended that we do not eat less than 15 – 20% of fat for highly active people. 

We also have recommendations for essential fatty acids

Linoleic Acid:

17 grams per day for men aged 19 – 50; 12 grams daily for women aged 19 – 50.

Alpha-linolenic Acid:

1.6 grams every day for men aged 19 – 50; 1.1 grams every day for women aged 19 – 50.