How Fat Provides Energy for Exercise

All the energy we need for life as well as for exercise comes from the food we eat and fluids we drink. These nutrients are commonly broken into three classes:

• Fats
• Carbohydrates
• Proteins

Each category of food is important for health and we should all consume foods from each category. The ratio in which we need to consume these foods, however, is often the topic of a debate.

Dietary fat has been blamed for many health problems; however, fat is actually an essential nutrient for optimal health. Adipose tissue (stored fat) provides cushion and insulation to internal organs, covers the nerves, moves vitamins (A, D, E, and K) throughout the body and is the largest reserve of stored energy available for activity. Fat is stored when we consume more calories then we use. There is an optimal level of body fat for health and for athletic activity. When that optimal level is exceeded, too much dietary fat can lead to problems with health as well as athletic performance.

• Saturated fats are found primarily in animal sources like meat, egg yolks, yogurt, cheese, butter, milk. This type of fat is often solid at room temperature. Too much saturated fat has been linked to health problems such as high cholesterol and heart disease. Because of this, saturated fat should be limited to no more than 10% of total daily calorie intake.
• Unsaturated fats include monounsaturated and polyunsaturated fats, which are typically found in plant food sources and are usually liquid at room temperature. Unsaturated fats have health benefits such as lowering cholesterol and reducing the risk of heart disease. Common food sources include olive and canola oil, avocados, fish, almonds, soybeans, and flaxseed.
• Trans fat has recently been added to the nutrition labels of most products. Trans fatty acids are created (naturally or man-made) when an unsaturated fat is made into a solid. Trans fats, like saturated fat, should be limited because they increase cholesterol levels and ​the risk of heart disease.

Fat provides the highest concentration of energy of all the nutrients. One gram of fat equals nine calories. This calorie density, along with our seemingly unlimited storage capacity for fat, makes fat our largest reserve of energy. One pound of stored fat provides approximately 3,600 calories of energy. While these calories are less accessible to athletes performing quick, intense efforts like sprinting or weight lifting, fat is essential for longer, slower lower intensity and endurance exercise such as easy cycling and walking.

Fat provides the main fuel source for long duration, low to moderate intensity exercise (endurance sports such as marathons, and ultra marathons). Even during high intensity exercise, where​ carbohydrate is the main fuel source, fat is needed to help access the stored carbohydrate (glycogen).

Using fat for fuel for exercise, however, is dependent upon these important factors:

• Fat is slow to digest and be converted into a usable form of energy (it can take up to 6 hours).
• Converting stored body fat into energy takes time. The body needs to breakdown fat and transport it to the working muscles before it can be used as energy.
• Converting stored body fat into energy takes a great deal of oxygen, so exercise intensity must decrease for this process to occur.

For these reasons, athletes need to carefully time when they eat fat, how much they eat and the type of fat they eat. In general, it’s not a great idea to eat fat immediately before or during intense exercise.