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November 29, 2023 10 min read

It is commonly understood that carbohydrates are the main fuel source for training and competition and protein is essential to enable muscle growth, repair, and recovery. But fat is often left out of the picture when talking nutrition for athletic performance and health.  

So, what should people interested in improving their health and physical performance know about dietary fat?

Dietary fat is one of the four macronutrients (the others are carbohydrates, protein, and alcohol). It is an essential component of a normal diet, providing energy and essential elements of cell membranes and associated nutrients such as vitamins A, D, E, and K.  

The acceptable macronutrient distribution range for fat is 20%-35% of energy intake(1) and the recommended proportion of energy from total fat intake should be 10% saturated, 10% polyunsaturated, 10% monounsaturated, and include sources of essential fatty acids.  

Fat provides ~9 kilocalories per gram and can be divided into four major categories:

  • Trans fats
  • Saturated fats
  • Monounsaturated fats
  • Polyunsaturated fats

Each category has a different chemical structure that inherently impacts the body in a distinctive way. Some very good, and some very bad.

Trans Fats

These are by far the worst for your health. Trans fatty acids are made by heating liquid vegetable oils in the presence of hydrogen gas and a catalyst called hydrogenation. Partially hydrogenating vegetable oils makes them more stable and less likely to become rancid (i.e., old & stale).

This process also converts the oil into a solid; making them function as margarine or shortening.

Partially hydrogenated oils can endure repeated heating without breaking down, making them ideal for frying fast foods. Therefore, partially hydrogenated oils became a mainstay in restaurants and the food industry for frying, baked goods, and processed snack foods and margarine.

In addition to partially hydrogenated oils, small amounts of trans fats are also naturally found in beef and dairy.

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(5), a reaction related to immunity – which has been implicated in heart disease, stroke, diabetes, and other chronic conditions.
  • Contribute to insulin resistance(4).
  • Even in small amounts, trans fats can have harmful health effects.  In fact, an additional 2% of calories consumed daily from trans-fat increased the risk of coronary heart disease by 23%

Saturated Fats

There are a mix of specific types of fats in all foods. Even healthy foods like chicken and nuts have small amounts of saturated fats, though much less than the levels in beef, cheese, and ice cream.

Essentially, saturated fat is mainly found in animal foods, but a few plant foods also contain high amounts, such as coconut, coconut oil, palm oil, and palm kernel oil.

  • The U.S. Department of Agricultures recommends getting less than 10% of calories each day from saturated fat.
  • The American Heart Association is more stringent with a recommendation of no more than 7% of calories(2) from saturated fat.
  • One thing to keep in mind is the negative impact of refined carbohydrates. Cutting back on saturated fat will likely have no benefit if it is replaced with refined carbohydrates. Eating refined carbohydrates in place of saturated fat does lower “bad” LDL cholesterol, but it also lowers the “good” HDL cholesterol and increases triglycerides. The net effect of this is it is detrimental to the heart.

The historic recommendations which are supported by the American heart Association and currently still in place by the U.S. Dietary Guidelines for Americans is to lower intake of saturated fat and replace it with unsaturated fats, especially polyunsaturated fats to reduce cardiovascular disease(3).

Paradigm shift in our understanding of saturated fats

The diet-heart hypothesis came about nearly 70 years ago due to the causal relationship between diet, cholesterol, and cardiovascular disease.  Essentially, this hypothesis postulates that reducing dietary saturated fat reduces serum cholesterol; thereby decreasing the risk of cardiovascular disease. This idea has been transformed from a hypothesis into public health policy for decades as current policy recommends reducing intake of saturated fat(4).  

The American Heart Association recommends lowering consumption of saturated fat and replacing it with unsaturated fats, ideally polyunsaturated fats to reduce cardiovascular disease(3).

To continue the limits on saturated fat, health officials must show ample and consistent evidence that these fats damage health. Many scientists argue that the historic guidelines and recommendations do not support the emerging evidence that is contradictory to this health policy.

There were many large, government-funded randomized-controlled trials conducted all over the world in the 1960s and 70s to test the diet-heart hypothesis. There were at least 75,000 people tested with hard endpoints (e.g., cardiovascular abnormalities) which are considered more definitive than LDL, HDL or total cholesterol levels. However, the outcomes of these trials did not support the diet-heart hypothesis, and were largely ignored or dismissed for decades, until recently when scientist began rediscovering them in the late 2000s.

Randomized controlled trials & Meta-analyses

Although they are difficult to conduct and have methodological problems, randomized controlled trials remain the best means for validating or rejecting a medical hypothesis. Recent examination of the literature identified 28 randomized controlled trials of diet lasting at least 1 year and reporting cardiovascular and/or mortality outcomes. Although about 50% (11 of 22 trials) reported statistically significant reductions in serum cholesterol, none of these reported a mortality benefit and only two reported a reduction in cardiovascular events.  

Out of the eight randomized controlled trials that specifically replaced saturated fat with various combinations of omega-3 and omega-6 polyunsaturated fats, none reported a mortality benefit and only two reported a reduction in cardiovascular events. Interestingly, two trials reported increased mortality and/or cardiovascular events with cholesterol reduction(5).  

The evidence indicates that the greatest benefit was seen when serum cholesterol was not lowered. Most of the cholesterol-lowering dietary randomized controlled trials, including those replacing saturated fat with polyunsaturated fat, were ineffective in reducing cardiovascular events or mortality. In addition, the results of most meta-analyses do not support the diet-heart hypothesis or the recommendation to replace saturated fat with polyunsaturated fat.

Importance of saturated fat and cholesterol

Although low-density lipoprotein cholesterol is targeted for reduction because of its role in atherosclerosis, cholesterol is essential for life as a key constitute of cell membranes and bile acids and a precursor of vitamin D and steroid hormones. 

Most animal fats are saturated and tend to raise serum cholesterol levels.

The key point is that we should not totally avoid cholesterol as it is an extremely crucial component for our health and physiological function.

Summary of saturated fats

Most of the evidence indicates that low-fat diets aimed to reduce cholesterol do not reduce cardiovascular events or mortality. Diets that replace saturated fat with polyunsaturated fat do not convincingly reduce cardiovascular events or mortality which is in opposition to current opinion(5).  

There are a few potential explanations for this:

  • We must consider that the diet-heart hypothesis is invalid or requires modification.
  • Some experts may selectively promote evidence that validates their own viewpoint and disregard evidence to the contrary. This is a behavior known as confirmation bias.
  • We must consider the limitations of targeting a single risk factor in a multifactorial disease.
  • The degree and/or duration of cholesterol reduction attained from diet may be inadequate.
  • The idea that replacing a macronutrient with another to prevent cardiovascular disease risks oversimplifies an extremely complex disease process.

Unsaturated Fats

Unsaturated fats, which are liquid at room temperature, are considered beneficial due to their ability to improve blood cholesterol levels, ease inflammation, stabilize heart rhythms, and several other beneficial roles. Unsaturated fats are mainly found in foods from plants, such as vegetable oils, nuts, and seeds.

There are two types of “good” unsaturated fats:

  • Monounsaturated fats are found in high concentrations in olive, peanut, and canola oils, avocados, nuts such as almonds, hazelnuts, pecans, and seeds such as pumpkin and sesame seeds.
  • Polyunsaturated fats are found in high concentrations in sunflower, corn, soybean, and flaxseed oils, walnuts, flax seeds, fish and canola oil.

Omega-3 fats are an essential type of polyunsaturated fat because the body can’t make them so they must come from food. An excellent way to get omega-3 fats is by eating fish 2-3 times a week. Good plant sources of omega-3 fats include flax seeds, walnuts, canola, or soybean oil.

Higher levels of omega-3 fats in the blood are associated with lower risk of premature death among older adults(6), but most people do not eat enough healthy unsaturated fats.

Research indicates that eating up to 15% of daily calories in place of saturated fat can lower heart disease risk(7).  

A recent meta-analysis examined the effects of carbohydrates and various fats on blood lipid levels. In those studies where polyunsaturated and monounsaturated fats were eaten in place of carbohydrates, these fats decreased levels of harmful LDL and increased protective HDL(8).  

In addition, a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart) demonstrated the value of replacing a carbohydrate-rich diet with one rich in unsaturated fat, predominantly monounsaturated fats.  This research showed that this change in diet lowered blood pressure, improved lipid levels, and reduced the estimated cardiovascular risk(9).

Omega 3s and Why They are The Ideal Fat for Physical Performance

There are many types of unsaturated fats, but two commonly known are Omega-3 and Omega-6 fatty acids. Most people get plenty of Omega-6 in their diet but not nearly enough Omega-3, which are typically inadequate in most daily diets.  Vegetable oils, commonly found in highly processed foods are rich in Omega-6 fatty acids.

Omega-3 rich foods include:

  • Fatty fish
  • Olive oil
  • Walnuts
  • Chia seeds and flax seeds

Three types of Omega-3 fatty acids are found in food. They are Alpha Linolenic Acid (ALA), Eicosapentaenoic Acid (EPA), and Docosahexaenoic Acid (DHA).

Omega-3's have many well-documented health benefits including heart health, weight management, and blood sugar control.

But Omega-3s also play a crucial role in muscle strength, endurance, recovery, and injury prevention for athletes including strength, endurance, and recovery.

Muscle Strength

Research indicates that Omega-3s enhance muscle protein synthesis, which increases muscle mass and strength. It seems that Omega-3s, specifically EPA improves protein metabolism(10).  

In addition, research indicates Omega-3s prevent the loss of muscle mass, meaning if you’ve sustained an injury and want to maintain muscle mass, adding Omega-3 could be a dietary tool to help maintain your body composition during healing(11).


Evidence suggests ingestion of Omega-3s can improve endurance capacity. Omega-3s act as a vasodilator, increasing oxygen flow during exercise, which increases endurance(12).  Other research indicates Omega-3s reduce fatigue(13).

Although limited; there is some research that supports Omega-3s’ potential for enhancing endurance.


Omega-3s are comprised of anti-inflammatory properties which help muscle recovery and injury prevention. The integrity of your cells and cellular function, which ultimately reduces muscular damage, is improved by consuming adequate amounts of Omega-3s. Just seven days of supplementation can decrease post-exercise muscle damage and soreness.  Additionally, Omega-3s have been shown to improve sleep, which is a vital piece of the puzzle for performance recovery(14).

In summary, it appears Omega-3s can help athletic performance by improving muscle strength, endurance, and reducing recovery time.

Omega-3 rich foods to include in your nutrition plan:

  • ALA is found in plant-based nuts, seeds, and oils.
  • EPA and DHA are found in fatty fish and marine algae.

Therefore, it’s recommended to consume two servings per week of low-mercury fatty fish such as salmon, sardines, or herring to meet 500mg per day of EPA and DHA. Generally, smaller fish have lower mercury content than larger fish, and wild fish have more Omega-3s than farm-raised fish.

Key takeaways on Omega-3s

  • Omega-3s can improve athletic performance by increasing muscle strength, endurance, and recovery.
  • Choose Omega-3 fats for health and performance benefits by incorporating more olive oil, walnuts, chia seeds, and flaxseeds.
  • Aim to consume at least two servings of fatty fish per week.
  • Consider supplementation as needed to reach the recommended levels, as per the above National Academy of Medicine recommendations.


Dietary fat, especially essential fatty acids play a crucial role in both health and physical performance. The consumption of the right amounts and type of fats can drastically change someone’s health and it can also change performance, recovery and overall results from exercise.

Along with the importance of quality protein and carbohydrate, I recommend paying attention to the amount and type of fat you consume. Also, ensure you are consuming enough of the essential Omega-3s in order to take advantage or their research-proven benefits.

Our understanding of saturated fats is changing as more and more scientists expose the past research that is not conclusive on the ill-effects of saturated fat.

It seems that the diet-heart hypothesis has flaws and the paradigm needs to be changed.  We will keep abreast of the latest information and research in this area and keep you informed.

Now that you understand the impact that different fats have on your health and performance, you can learn the surprising truth about how low-carb diets jeopardize muscle growth and high-intensity exercise here.

    1.    Medicine. Io: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington (DC), The National Academies Press, 2005
    2.    American Heart Association Nutrition C, Lichtenstein AH, Appel LJ, et al: Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee. Circulation 114:82-96, 2006
    3.    Farvid MS, Ding M, Pan A, et al: Dietary linoleic acid and risk of coronary heart disease: a systematic review and meta-analysis of prospective cohort studies. Circulation 130:1568-78, 2014
    4.    Riserus U, Willett WC, Hu FB: Dietary fats and prevention of type 2 diabetes. Prog Lipid Res 48:44-51, 2009
    5.    Mozaffarian D, Pischon T, Hankinson SE, et al: Dietary intake of trans fatty acids and systemic inflammation in women. Am J Clin Nutr 79:606-12, 2004
    6.    Molfino A, Gioia G, Rossi Fanelli F, et al: The role for dietary omega-3 fatty acids supplementation in older adults. Nutrients 6:4058-73, 2014
    7.    Mozaffarian D, Micha R, Wallace S: Effects on coronary heart disease of increasing polyunsaturated fat in place of saturated fat: a systematic review and meta-analysis of randomized controlled trials. PLoS Med 7:e1000252, 2010
    8.    Mensink RP, Zock PL, Kester AD, et al: Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials. Am J Clin Nutr 77:1146-55, 2003
    9.    Appel LJ, Sacks FM, Carey VJ, et al: Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA 294:2455-64, 2005
    10.    Smith GI, Atherton P, Reeds DN, et al: Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperinsulinaemia-hyperaminoacidaemia in healthy young and middle-aged men and women. Clin Sci (Lond) 121:267-78, 2011
    11.    Gammone MA, Riccioni G, Parrinello G, et al: Omega-3 Polyunsaturated Fatty Acids: Benefits and Endpoints in Sport. Nutrients 11, 2018
    12.    Kawabata F, Neya M, Hamazaki K, et al: Supplementation with eicosapentaenoic acid-rich fish oil improves exercise economy and reduces perceived exertion during submaximal steady-state exercise in normal healthy untrained men. Biosci Biotechnol Biochem 78:2081-8, 2014
    13.    Byelashov OA, Sinclair AJ, Kaur G: Dietary sources, current intakes, and nutritional role of omega-3 docosapentaenoic acid. Lipid Technol 27:79-82, 2015
    14.    Patan MJ, Kennedy DO, Husberg C, et al: Differential Effects of DHA- and EPA-Rich Oils on Sleep in Healthy Young Adults: A Randomized Controlled Trial. Nutrients 13, 2021

Dr. Paul Henning

About Dr. Paul

I'm currently an Army officer on active duty with over 15 years of experience and also run my own health and wellness business. The majority of my career in the military has focused on enhancing Warfighter health and performance. I am passionate about helping people enhance all aspects of their lives through health and wellness. Learn more about me