Dietary fats, or fatty acids, have been unfairly demonized for causing health issues despite being required for every physiological system in the body, making them an essential nutrient. As the most energy-dense macronutrient, fat delivers 9 calories per gram. Fats give food flavor and texture, making them palatable and desirable, which is beneficial because fats serve numerous vital physiological functions.

The body can synthesize most fatty acids necessary for its functioning, except for the two essential fatty acids of Linoleic acid (an Omega-6 fatty acid) and Alpha-Linolenic acid (an Omega-3 fatty acid). These essential fatty acids cannot be produced by the body and must be obtained through the diet. They play crucial roles in cell membrane structure, brain and nerve function, immune response, and inflammation regulation, and more.

Structure

Fats are classified as either saturated or unsaturated, with unsaturated fats further divided into monounsaturated and polyunsaturated fats. The key difference between these types of fats lie in the arrangement of their chemical structure, known as chains. The length of these chains influence the stability of a fat, which is most easily observed in how they behave at room temperature.

Saturated fats have a straight and simple structure, with all the spaces in their chain filled. This allows the molecules to pack closely together, making them more stable and less likely to react with other substances, like oxygen. As a result, saturated fats are generally solid at room temperature. Examples include butter, ghee, and coconut oil.

Unsaturated fats have at least one bend in their chain, caused by a gap. This bend prevents the molecules from packing closely together, making them less stable and more likely to react with other substances, such as oxygen. Consequently, unsaturated fats tend to be liquid at room temperature. The main difference between monounsaturated and polyunsaturated fats lies in the number of gaps present in the chain.

• Monounsaturated fats have a single gap in their chain. Examples include olive oil, avocado oil, and certain nuts like almonds and peanuts.
• Polyunsaturated fats have two or more gaps in their chain. They are less stable and more prone to oxidation than monounsaturated fats. Examples include omega-3 and omega-6 fatty acids found in fish oil, flaxseed oil, and soybean oil.

The longer and more complex the chain, the more unstable the fat, and the greater the incidence of reacting with oxygen. Such reactions can be detrimental because they can lead to the process of oxidation. Oxidation can cause the fat molecules to break down, producing harmful byproducts called free radicals. These free radicals can damage cells, proteins, and DNA in the body, contributing to inflammation, aging, and the development of various diseases. Therefore, it becomes important to treat monounsaturated and polyunsaturated fats with more care, paying particular attention to the way you source, store, and prepare them.

Additionally, while fats can be categorized as saturated, monounsaturated, or polyunsaturated, it is essential to understand that most foods contain a combination of these types. However, we generally identify them according to the type of fat that is present in the largest amount.

Function

Dietary fats plays a crucial role in the overall health and functioning of the human body. Its diverse functions range from nutrient absorption to hormone synthesis and brain health. Let's take a closer look at these functions and their importance:

• Nutrient absorption: Dietary fats play a crucial role in the absorption of fat-soluble vitamins (A, D, E, and K), which are essential for various bodily functions. These vitamins contribute to healthy vision, immune system function, bone growth, blood clotting, and antioxidant activity.
• Cell membrane function: Fats are vital components of cell membranes, helping maintain their structure and fluidity. This support is essential for proper cell function and communication, allowing cells to exchange nutrients, waste products, and signals with their environment.
• Brain and nervous system health: Fats, particularly omega-3 fatty acids, are essential for maintaining the structural integrity of the brain and nervous system. They contribute to cognitive function, memory, and mood regulation. Furthermore, fats are involved in nerve communication and the formation of myelin sheaths, which protect nerve fibers and facilitate efficient signal transmission.
• Hormone synthesis: Fats provide the structural components for the synthesis of steroid hormones, which regulate various physiological processes such as metabolism, immune function, and reproduction. These hormones include cortisol, aldosterone, and sex hormones like estrogen and testosterone.
• Insulation and protection: Fat serves as an insulating layer beneath the skin, helping to maintain body temperature in cold environments. Additionally, fat cushions and protects internal organs from physical impact, reducing the risk of injury.
• Energy storage: Fats act as an energy storage substrate, providing a concentrated source of energy when needed. They are particularly important during fasting or prolonged low-intensity activities when the body requires a steady energy supply.
• Satiety and flavor: Fats contribute to the taste and texture of food, making it more palatable and satisfying. They also promote satiety by slowing down digestion and the release of hormones that signal fullness, helping to regulate appetite and prevent overeating.
• Immune function: Some fatty acids, such as omega-3s, have anti-inflammatory properties and can modulate immune responses, thereby promoting overall immune system health.
• Skin and hair health: Fats are essential for maintaining healthy skin and hair. They help to keep the skin moisturized and supple, while also supporting the structure and growth of hair.
• Blood clotting and inflammation: Omega-3 and omega-6 fatty acids play a vital role in regulating blood clotting and inflammation in the body, helping to maintain cardiovascular health and prevent chronic diseases.

Role in Muscle Building: A few decades ago, the concept of the "anabolic window of opportunity" was popular in fitness and nutrition circles. It was believed that avoiding fat in post-exercise meals would improve recovery and muscle growth by preventing slowed gastric emptying, which could interfere with glycogen resynthesis and hinder the anabolic response. However, this idea is now largely considered to be unfounded, unless you're a competitive endurance athlete with a very short time frame between training sessions.

The idea that post-exercise fat consumption could slow absorption and blunt the insulin response, thus negatively impacting muscle protein synthesis (MPS), has been debunked by various studies. One such study by Elliot and colleagues1 compared the effects of fat-free milk, whole milk, and a calorie-matched dose of fat-free milk (to match the calories of the whole milk) consumed 60 minutes after resistance exercise. The results showed that whole milk was superior for increasing net protein balance, despite the calorie-matched dose of fat-free milk containing 81% more protein.

The researchers explored various possible mechanisms to explain the outcome, such as the insulin response, blood flow, and individual subject response differences. However, they eventually dismissed each hypothesis, concluding that more research is needed to fully understand the role of fat in post-exercise nutrition.

Similar results were observed in a study by van Vliet and colleagues2, which compared post-exercise consumption of an isonitrogenous (protein-matched) dose of egg whites versus whole eggs. The whole eggs proved superior for stimulating muscle protein synthesis (MPS), even in resistance-trained subjects.

In a 12-week trial by Bagheri and colleagues3, the effects of consuming three whole eggs versus six egg whites post-exercise in resistance-trained men were compared. The whole egg group experienced greater lean mass gains (3.7 kg or 8.14 lbs) compared to the egg white group (2.9 kg or 6.38 lbs), although the difference was not statistically significant. Both groups experienced a decrease in fat mass, but the decrease in body fat percentage was significantly greater in the whole egg group. Additionally, the whole egg group saw significantly greater gains in knee extension and hand grip strength.

Another factor that may have contributed to the benefits of whole eggs in this study is their impact on testosterone levels. The whole egg group experienced a 240 ng/dL increase in testosterone, compared to a 70 ng/dL increase in the egg white group😃. While the clinical significance of this testosterone increase is open for debate, it is plausible that it could have contributed to the anabolic process beyond the extra calories from the fat content in the egg yolks.

These studies suggest that consuming dietary fat post-exercise, particularly from whole food sources such as whole milk and whole eggs, may have a positive impact on muscle growth and strength gains. While more research is needed to fully understand the mechanisms behind these effects, it seems that dietary fat may play a beneficial role in muscle building when consumed as part of a balanced post-exercise meal.

Intake

Dietary fat guidelines are typically presented as a proportion of total caloric intake, with the Institute of Medicine's Acceptable Macronutrient Distribution Range (AMDR) recommending that 20-30 percent of an individual's daily caloric consumption coming from dietary fats. It is relatively rare to find any recommendations expressed in grams per pound of body weight or lean body mass. This is unlike proteins and carbohydrates, which have numerous examples in the scientific literature, where recommendations are almost exclusively expressed in grams per pound. The limited amount of published research that does list fat intake recommendations, all boils down to observational studies, many of which come from the bodybuilding sphere.

For example, a recent review by Iraki and colleagues4 on the nutritional requirements of physique competitors in the off-season recommends a fat intake ranging between 0.23-0.68 g/lb, while another study by Ruiz-Castellano and colleagues5 on dieting resistance-trained athletes recommends 0.23-0.45 g/lb. It's worth noting that a dietary fat intake of 0.23 g/lb is likely too low to be sustainable for individuals who are already lean or within normal weight ranges.

Another study by Chappelle and colleagues6 involving high-level natural bodybuilding competitors has reported fat intake ranging from 0.18-0.36 g/lb during contest preparation. While a recent systematic review by Whittaker and Wu7 provided evidence that extreme low-fat diets (averaging under 20 percent of total calories) decreased testosterone levels compared to their higher-fat counterparts (averaging closer to 40 percent of total calories).

Taking these into consideration, it is safe to say that maintaining a minimum fat intake of 0.32 g/lb is a safe place to start as it prevents the fat intake from dropping below 20% of total calories, thus helping to protect against potential excessive drops in such things as testosterone and other hormones necessary for optimal health and functionality.

Alternatively, finding the upper-end is slightly more difficult. The AMDR's 35 percent cutoff for dietary fat is arbitrary and likely too restrictive for clients who will commonly be embarking on a low-carbohydrate or ketogenic dietary approach (at least, initially).

Consider, a rather typical, but hypothetical situation, where an individual is on a 2,000 kcal diet, with 150 grams (600 kcal) of protein. This person is also restricting carbohydrates to 100 grams (400 kcal), leaving them with 1,000 kcal from fat (111 grams), which amounts to 50 percent of their calories. This significantly exceeds the AMDR, but there is no inherent issue with this dietary approach.

This example can be taken a step further by applying it to someone restricting their carbohydrate intake to ketogenic levels (50 grams or less), which would result in a fat proportion of 65 percent—nearly double the AMDR's upper limit. Ketogenic diets are not inherently problematic; they are merely one tool in the toolbox. Like any diet, the food sources can determine their relative healthfulness.

For practical purposes, the 35 percent upper limit for dietary fat intake established by the Institute of Medicine should be considered as a flexible guideline rather than a strict rule, allowing for individualized dietary approaches based on personal needs and preferences. To make it easy and set a general guideline, there likely isn't much need to exceed a fat intake of 1 g/lb. Therefore, we can conclude by taking into account the collective evidence, an appropriate range of dietary fat intake for our clients purposes and goals will be 0.32 to 1 g/lb. Obviously, this is a large range, so after protein is accounted for, you will have to decide what will be the best approach for the client — a higher fat, lower carb approach or a lower fat, higher carb. While higher fat, lower carb will likely work better for metabolically challenged clients, both options have been shown to work for weight loss, and it really comes down to preference.

Fat Dosing Cheatsheet