Everything You Need to Know About Dietary Fats

by on November 15, 2014

Everything You Need to Know About Dietary Fats


Here’s what you need to know, consuming dietary fats doesn’t make you fat. Consuming too many calories that your body can’t metabolize gets you fat. In fact, fats are an essential macronutrient that our bodies need. Fats are the most energy-dense macronutrient and they provide many of the body’s tissues and organs with most of their energy.

Fat is the most critical macronutrient to optimize hormonal functions (i.e., testosterone, libido, etc.) Fats are also important for (1):

  • Building muscle
  • Reducing cortisol levels
  • Providing energy
  • Satiety purposes
  • Slowing the digestion of carbs
  • Assisting the body in functioning properly

Don’t fall into the fitness dogma of fats are bad for you and if you consume them they will make you fat. It’s one of the most ridiculous myths out there, our bodies need fat, and we are going to tell you why in this article.

Metabolism of Lipids

It can be pretty complex when you stop and think how Lipids (fats) are metabolized and utilized from a physiological stand point. Let us briefly run you through step by step how the process works through Lipolysis and B-oxidation.

Lipids are stored in the body as Triglycerides or Triaglycerols; you may have seen the abbreviation for these terms (TAGs). Once Lipids are stored they are broken down and become a useable form of energy known as “Fatty Acids.”

Let’s get back to this popular abbreviation TAGs. Lipids can be found as TAGs in adipose tissue, muscle, and in blood in the form of lipoproteins. TAGs have to be broken down to fatty acids and “Glycerol” before being used as an energy source. (2) This is known as the popular scientific term floating around us “Lipolysis” which we will get more into briefly.

A triglyceride or triaglycerol is in effect a glycerol molecule which provides the backbone to which are attached three fatty acyl units. Glycerol, when released, is normally metabolized by the liver to produce energy, or it can be converted to glucose via “Gluconeogenesis”. (2) From there, fatty acids are taken up by the muscle and liver, where they undergo beta-oxidation also known as “B-oxidation” (which we will get into further along) before entering the TCA cycle and undergoing further oxidation to carbon dioxide and water.


Lipolysis is the process whereby Triglycerides are broken down to Glycerol and Fatty Acids. This process is regulated by hormones such as the Insulin and the Catecholamines. (2) The process of lipolysis takes place in adipose tissue and also in muscles, so be aware that muscle cells do contain triglycerides. Lipolysis occurs during exercise and also some hours (around six or more) after a meal when fatty acids are needed as an energy source by various tissues. Lipolysis does occur within a few hours (1-2 hours) after a meal; particularly if the meal is high in carbs.

It is very important to know that fatty acids and glycerol are released by adipose tissue as a result of lipolysis pass out of the adipocyte into the blood. The glycerol is soluble, whereas the fatty acids are bound to “Albumin” molecules in the blood. Albumin molecules are proteins and have the capacity to carry up to ten fatty acid molecules each. The amount of fatty acids delivered to the muscle from adipose tissue is dependent on the blood flow through the adipose tissue and on the numbers of albumin molecules in the blood. (2)

Once fatty acids are inside the “Cytoplasm” of the muscle cell, fatty acids are bound to another fatty acid binding protein (FABP), by which they are transported to the mitochondria. At the outer membrane of the mitochondria, the fatty acids are activated by the enzymes ACS and CoA, and thus become activated fatty acids. Let’s delve into B-oxidation shall we.


B-oxidation occurs in the mitochondria, where a repeat cycle of four reactions cleaves an acetyl-CoA, so reducing the fatty acid by two carbons. Each cycle of B-oxidation results in the generation of five ATP and the acetyl-CoA produced then enters the TCA cycle for complete oxidation. Remember that the fatty acids consist of carbon, hydrogen, and oxygen.

Two very important points to keep in mind: first, that a great amount of energy arises from fatty acid oxidation (certainly more than from glucose): and second, that fatty acids are only used during aerobic activities since the TCA cycle and oxidative phosphorylation are involved. (2)

Lipids and Hormones

Since fat is responsible for optimizing hormonal functions, such as testosterone, this doesn’t mean to go down to Costco or Sam’s and purchase a tub of Crisco and go to town on it every day. Remember that fats are the most energy dense macronutrient (9 kcals/gram) and they can be easily stored as adipose tissue (body fat). So you must be aware of what your body metabolizes better through carbohydrates or fats because it will be up to you to play the trial and error game.

Several studies concluded that diets low in fat (under 15% of total calories) significantly decreased testosterone levels while diets higher in fat (above 30% of total calories) increased serum testosterone levels. (3) To make things easier for you, it seems that one should not lower fat below 15% of daily calories unless they would like to see their testosterone levels plummet.

On the contrary, you should not increase fat to over 40% in order to increase testosterone. But again, this is just a rough estimation and you have to try things out for your body. You might be able to go over 40% and make solid gains or you might start adding fat. Although fat increases testosterone to a degree, it is important to remember that testosterone is only a small piece of the larger pie. There are many other hormones and factors involved in building muscle other than just testosterone.

By increasing fat to extremely high levels, there will be less “space” for carbohydrates and protein, both of which are very important for building muscle mass. Just be sure not to look at consuming fat in a linear fashion, as moderation is the key to everything in life.

There is a high degree of variability the way individuals respond to diets. Carbohydrate and fat utilization as a percentage of energy expenditure at rest and various intensities has as much as four fold differences between individual athletes; Which is influenced by muscle fiber composition, diet, age, training, glycogen levels and genetics. (4) Individuals that are more insulin sensitive may lose more weight with higher carbohydrate low fat diets while those more insulin resistant may lose more weigh with lower carb and higher fat diets.

Why Fats are Important

Body Composition

We touched briefly in the intro on some of the reasons we need fats in our diets. Dietary fat is an essential macronutrient for both health and optimal body composition.

Dietary fats are important for optimal body composition through the production of testosterone. A 1983 study from the Journal of Steroid Biochemistry showed reductions in the percentages of dietary fat from 40-20% have shown reductions in testosterone levels (5, 6). The research is pretty clear on eating a lower fat diet and testosterone lowering, but this doesn’t mean that your testosterone levels will completely plummet, you will lose all the gains you made, and that you shouldn’t eat lower than 40% of your calories from fats. Testosterone will decrease a bit when dieting and a big part of this is from the rate of weight loss. The goal is to try and lose as much weight as slowly as possible and to mitigate big drops in testosterone.

To support the above claim, Volek et al. showed correlations between testosterone levels, macronutrient ratios, types of fats, and total dietary fat, illustrating a complex interaction of variables (7). Moreover, if a reduction in fat is utilized, it may be possible to attenuate a drop in Testosterone levels by maintaining adequate consumption of saturated fats (8).

So as you can see it’s crucial to have fats in your diet to keep testosterone levels as high as possible and thus aiding in muscle growth. How much is going to depend on a lot of factors, more on this in the latter part of the article.

Overall Health

Dietary fats are also very important for overall health and reducing inflammation. Omega-3 fatty acids have a well-documented anti-inflammatory effect. Experimental models examined the hypothesis that omega-3 fatty acids could attenuate injury by reducing the inflammatory response though the reduction of the formation of pro-inflammatory group 2 eicosanoids (1).

The omega-3 PUFA’s (polyunsaturated fatty acids) found in fish oil also helps to optimize adipocyte (fat cell) function by decreasing the secretion of inflammatory factors, and improving the profile of adipokines towards one of increased insulin sensitivity, regulated appetite, and shunting nutrients such as amino acids (protein) and glucose (carbs) toward lean body mass and away from fat mass (9).

Much research has gone into the effects of essential fatty acids (EFA’s), especially the long chain omega-3 PUFA’s most notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), also commonly known as “fish oils.” They have been investigated for their possible cardiovascular health and body composition effects.

PUFA’s are also good for insulin sensitivity (able to lower carbs) and protein synthesis (muscle growth). Overall, daily fish oil through supplementation or through food sources along with a proper nutrition and training programs augments lean muscle tissue mass, could help oxidize adiposity, helps reduce inflammation, and is beneficial for cardiovascular health.

Different Types of Fat Sources

When it comes to choosing fat sources we hope you don’t just think you have a limited amount of sources to choose from like butter, Crisco, lard, fats from the end of meats, etc. There are four different types of dietary fats and here are some food sources to choose from when looking to incorporate dietary fats:

  • Polyunsaturated fats (PUFA’s) which consists of: Corn, safflower, sesame, canola, soy, and sun flower oils; some nuts and seeds. The best sources of omega-3 PUFA’s come from cold water fish such as herring, mackerel, salmon, sardines, tilapia, tuna, flax seeds, and walnuts.
  • Monounsaturated fats (MUSFA’s) which consists of: Olive, canola, and peanut oils; Nuts, avocados, and peanut butter or almond butter spreads
  • Trans fats (TFA’s) Which consist of butters, lard, baking shortenings, and fast foods
    **Trans fats- trans-fatty acids (may be listed as hydrogenated oils) as they are very difficult for the body to metabolize and are also easily stored as fat. Making it easier for the body to metabolize them and they are to be avoided as much as possible due to the risk of coronary heart disease.
  • Saturated fats (SFA’s) which consists of: Cheeses, milks, animal fats, some candies and butters, and eggs.
    Saturated fats seem to help with increasing testosterone, aim for approx. 30% of saturated fats out of total fat intake for the day (10).

Now that you know the different kinds of fat sources and what foods you can find them in, let’s talk about fat intake and how much you need.

Fat Intake

Previously, we just discussed the different kinds of fat sources and what foods you can find them in. Now it’s time to learn about how much fat you actually need in your nutrition program.

It seems that the research has a very solid recommendation of a 15-30% of fat intake of total caloric intake being adequate, but keep in mind the higher the fat is set the more you compensate protein and carbs; therefore it may be wise to aim for a 15-20% fat intake to keep more carbs and protein in due to them being more metabolic, anabolic, and muscle sparing (5, 11).

The International Society of Sports Nutrition recommends 30% of your diet should be made up of fats. 10% polyunsaturated fats (flaxseed oil, fish oil, fish), 10% monounsaturated fats (nuts, olive oil, avocados), & 10% saturated fats (fats from meats, egg yolks). This is also known as the “Rule of 10.” Studies have shown that 30% is the maximum percentile that the body will use fats for good measures (1).

So if we take a 200 lb subject that is eating 3,000 calories and starting a cutting phase, his macronutrient profiles may look as so:
Protein- 220g
Carbs- 305g
Fats- 100g

30% of this subject’s diet is made up of fats. If they were to follow the rule of 10, his dietary fats consumption would look as so:
Approx. 33g of fats coming from saturated fats
Approx. 33g of fats coming from polyunsaturated fats
Approx. 33g of fats coming from monounsaturated fats

Notice this subject has 30% of his diets calories coming from fats, he has an excellent balance of SFA, PUSFA, and MUSFA’s, his entire macronutrient ratios are balanced. This subject is set up to have a successful cutting phase.

So as long as you comprise your diet anywhere from 15-30% of fats you should be in good shape to get all of the great benefits from dietary fats.

Wrapping this up

Now that you know the importance of dietary fats and how important their role is to the human body it really should make you appreciate this essential macronutrient. Whatever your goals or personal preferences are, as long as you understand the basics of lipid metabolism, why they are important, different types of fats, how much to consume, and how they help hormonal wise, you should be very confident in how to use dietary fats throughout your daily diet. Now go out and enjoy some Almond or Peanut Butter!



1. Smith Ryan, Abbie. Antonio, Jose. Sports nutrition and performance enhancing supplements. 2013

2. Don Maclaren, James Morton. Biochemistry for Sport and Exercise Metabolism.2012

3. Joanne F. Dorgan; Joseph T. Judd; Christopher Longcope; Charles Brown; Arthur Schatzkin; Beverly A. Clevidence; William S. Campbell; Padmanabhan P. Nair; Charlene Franz; Lisa Kahle; Philip R. Taylor. “Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men: a controlled feeding study.” American Journal of Clinical Nutrition, Dec 1996.

4. Dyck DJ, Heigenhauser GJ, Bruce CR. “The role of adipokines as regulators of skeletal muscle fatty acid metabolism and insulin sensitivity.” Acta Physiol (Oxf). 2006

5. Hamalainen et al. Decrease of serum total and free testosterone during a low fat high fibre diet. 1983

6. Dorgan et al. Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men. 1996

7. Volek et al. Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. 1997

8. Lambert et al. Macronutrient considerations for the sport of bodybuilding. 2004

9. Sahine-Efe et al. Advances in adipokines. 2012

10. Sebokova et al. Alteration of the lipid composition of rat testicular plasma membranes by dietary fatty acids changes the responsiveness of leydig cells and testosterone synthesis. 1990

11. Bird SP. Strength nutrition. Maximizing your anabolic potential. 2010