You may have heard of the concept of “carb loading” before a big race to build up energy stores. However, did you know that dietary fat is really the source of long term fuel in endurance sports such as running? While most emphasis is put on carbohydrate intake, dietary fat is also an essential part of a runner’s diet. Here we will explore dietary fat in relation to a runner’s diet, timing of when to eat fat and the type of fat to eat to ensure you reach peak performance.
Dietary fats are an essential part of a healthy diet, meaning you must obtain most fats through the food you eat. Fats have many roles in your body including supporting cell growth, protecting your organs, helping keep your body warm, as well as absorbing some nutrients and producing important hormones, too (1). For athletes, especially endurance athletes, when the stored glycogen in your muscles from carbohydrates is burned up, your body turns to fat for long term fuel. It is important to eat the right amount and type of fat.
While fat is an essential part of your diet, the type of fat you eat also makes a difference. Certain types of fats are healthier than others and will better support overall functioning and performance. Types of dietary fats include:
Saturated fat: Saturated fats are best identified by their chemical structure, and are usually solid at room temperature (2). They are naturally occurring in many foods and mainly come from animal sources such as fatty beef, pork, and full fat dairy products such as cheese, cream and butter but can also be found in tropical oils such as coconut and palm oil. The human body makes all the saturated fat that it needs, so it is not necessary to get saturated fat from food (3). However, many individuals exceed the recommended limits of saturated fat in the diet. Based on the suggestion that diets higher in saturated fat are associated with an increased risk of developing cardiovascular disease, it is recommended that the amount of saturated fat consumed is limited to less than 10% of calories per day (3).
Trans fats: While trans fats can also be naturally occurring in some animal foods, it is the artificial trans fats that have gained a bad reputation for the negative impact they have on health. Artificial trans fats are manufactured through a method called hydrogenation, where hydrogen is added to liquid oils to make them more solid (4). Due to this process, processed trans fats can often be found on the ingredient label as “partially hydrogenated oils”. Trans fats are often found in fried foods and baked goods including foods like doughnuts, cakes, pie crusts, biscuits, cookies, crackers, and stick margarines and other spreads. Like saturated fat, trans fat can increase blood cholesterol levels (5). It is recommended that the consumption of trans fats be significantly limited due to its negative health impact
Monounsaturated and polyunsaturated fats: Oils that contain monounsaturated or polyunsaturated fats are typically liquid at room temperature but can start to turn solid when chilled (6). Monounsaturated fats can be found in high amounts in plant-based oils such as olive oil, canola oil, peanut oil, and foods such as avocado, nuts and sesame seeds. Polyunsaturated fats can also be found in plant-based oils such as corn oil, soybean oil and sunflower oil, or foods such as flax seeds and walnuts. These fats are referred to as "good” or “healthy" fats because they can lower your bad (LDL) cholesterol (6).
Oils rich in mono and polyunsaturated fats also contribute vitamin E to the diet (6). Foods that contain polyunsaturated fats also provide your body with fats that it cannot produce itself and must be obtained from the diet – such as omega-6 and omega-3 fats (7). While there is no daily recommendation for the amount of mono or polyunsaturated fats to eat, it is recommended to try to incorporate more monounsaturated fats into your diet than saturated or trans fats, as they can have a positive effect on your health, when eaten in moderation.
For endurance athletes, their body aims to use up stored carbohydrates as slowly as possible, and muscles often turn to fats for a long-term energy source. It is recommended that the majority of the fats consumed come from foods that are rich in mono and polyunsaturated fats instead of foods containing saturated and trans fats. To fuel longer runs, meals rich in healthy unsaturated fats are highly recommended as part of an overall healthy diet (8). On average, it is suggested that athletes should consume 20 to 35 percent of their calories from fat (9).
Although fat is needed for long-term energy, choosing when to eat fats is also important for athletes. Fatty foods can slow digestion and possibly lead to an upset stomach if eaten too close to training or sports, so it's a good idea to limit eating high fat foods at least a few hours before exercising. It is more important for endurance athletes to eat the proper amount of fats over a period of time to support adequate training, performance and recovery.
While carbohydrates are still the main source of energy for athletes, runners should take specific care to include healthy fats into their diets. As runners train, their bodies can learn to more efficiently use fat for fuel to save carbohydrates and prevent fatigue during a race. It is also important to consume the right types of fats, making sure to eat more healthy unsaturated fats rather than saturated or trans fats. Not sure that you are getting the right amount or type of fat? Nutrition apps such as Lifesum can help you track your fat intake and make suggestions for healthier fat options. What is your favorite healthy fat that fuels your runs?
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