For many years now, the talk of fat, or the consumption of fat, always seems to come with a negative connotation, or a confusing, misunderstood message, especially because of their higher concentration of 9kcals/gram, compared to their macronutrient counterparts which only contain 4kcals/gram. However, researchers have now concluded the importance of consuming fats in our diet, and how vital they are to general health, and exercise performance. Fat is important in all humans, though it does play much more of a key role in the diet and lifestyle of endurance athletes.
What are lipids?
There are two main categories, and three sub-categories of lipids (Saturated and unsaturated: monounsaturated, polyunsaturated, and, trans fats) [see Table 1]. The fats which are found in our body’s typically fall in to one of three groups: triglycerides, phospholipids (lecithin), and, sterols (cholesterol). With just a single gram of fat containing 9kcals, we can store on average ~80,000kcals of stored energy, which for athletes may be an essential fuel source, especially in such extreme events as ultra-marathons, multi-day adventure racing, multi-stage cycling, and Ironman events.
Table 1: Types & Functions of Fat in the Body
Often linked to development of chronic diseases such as cardiovascular disease. However, latest evidence may suggest otherwise.
Avocado, Bacon, Brazil nuts, Cream, Cheese, Lard, Red meats, Tofu, and Tempeh.
|Mono-unsaturated fat||Provides a potential source of energy. Have been linked to positive health outcomes.||Avocado, Olives, Meats, Milk, and Nuts.|
|Polyunsaturated fat||Omega 3 & 6 fatty acids in particular have a role in inflammation and immunity. Increases the membrane fluidity of cells.||Fish, Nuts, Soy beans, and Sunflower seeds.|
|Trans fats||Generally harmful for the body.||Processed foods.|
Table 1: Adapted from ‘Performance Nutrition’ Currell, K. (2016)
Digestion & Metabolism?
The digestion of fats begins in the mouth, moves in to the stomach, travels through the lymphatic system (part of the circulatory and immune systems), and finishes off at the individual cell, where they can become part of the cell membrane (1). Once digested, lipids are packaged in to chylomicrons, and upon reaching their target cells are stored, or used depending on the physiological state of the individual ie: active or sedentary.
Muscular contractions during physical activity allows a process called lipolysis & oxidation to occur which induces fat breakdown and burning, whereas the lack of muscle contractions in more sedentary individuals induces fat storage; a process called lipogenesis.
It is this physical activity, or lack of as the case may be which changes the mobilization of how stored fatty acids are used in our bodies. It is true, that the more trained the individual is the higher their ability to be able to utilize fat as a fuel substrate, however, one thing does stay the same whether you are well-trained, slightly-trained, or a sedentary individual, and that’s the individual ratio at which fat is used with regards to the duration and intensity of one’s activity. The longer that an individual exercises for at a low-moderate intensity the greater their ability to breakdown and use fat as fuel. On the contrary, the harder the intensity of activity, the less fat can be contributed as a fuel source, and carbohydrates take over as the primary substrate.
Types & Sources of Fat:
Fats come in several forms, and I am sure most of us are aware that some are healthier than others. As a general guideline, the unsaturated fats of polyunsaturated (Omega 3 & 6 fats) and monounsaturated are deemed as healthier fats, saturated fat should be kept to a minimum of ~10% of total fat consumption per day, whereas hydrogenated and trans-fats are generally recommended to be avoided within our diets. The recommended daily allowance (RDA) for fat consumption set out by the American Heart Association (AHA) ranges between 15-30% of total daily calories (2), however this is very dependent on the individual and their personal goals of body composition and physical performance.
Exceeding the recommended range of consumption will typically increase the risk of such issues as unwanted weight-gain, cholesterol, and heart disease. Consequently, consuming too little fat also has the potential to cause adverse physiological effects via essential fatty acid insufficiency in some individuals. This can be caused by the lack of linoleic acid (Omega-6) and alpha-linoleic acid (Omega-3) which are two essential fatty acids which we must consume through the foods which we eat, as our bodies are unable to synthesize these fatty acids.
When it comes to exercise performance, consumption recommendations are typically increased, with up to 50% of caloric daily intake coming from fats. However, this is only recommended in those athletes who use prolonged periods of heavy, intense training (3).
To help athletes understand and manage their own fat consumption it is best to educate them about which types of fats are in which particular foods, as this will allow them to make better food choices in day-to-day living, training, and during events when faced with food choices at check-points and time-control points, (‘Check-point foods’ will be discussed in a future article so watch out for that one!).
What are the functions of fat?
The consumption of fat in our diet is essential for several reasons, including an essential fuel source, maintaining the integrity of cell membranes, helping to play a key role in growth, reproduction and skin & tissue maintenance, as well as general body functioning. Fat also plays a vital role in the transport and absorption of the fat-soluble vitamins A, D, E and K, as well as the Carotenoids. Fat can also help to flavour foods and make our meals much more filling and satisfying.
Dietary fats are slowly gaining a more health-conscious reputation among the public due to the extensive research projects which are continually carried out across the world, and are now highlighting the associated health benefits with fat consumption. The most well-known understanding of fat currently, is that not all fats are alike, and therefore not all fats are digested, metabolised, and utilized in the same way in our bodies, as they are also not digested, metabolised, or utilized in the same way as other macronutrients. Fats are unique, with their slower gastric emptying, to their lymphatic transport role, they are far more than an energy substrate…so in conclusion, fats are both friend & foe!
- Fat is important for all humans, though it does play much more of a key role in the diet and lifestyle of endurance athletes
- Fat is a source of nutrients known as essential fatty acids
- Fat is more calorie dense than carbohydrate and protein and contains 9kcals/gram
- We can store on average ~80,000kcals of stored energy, which for athletes may be an essential fuel source
- It is the muscle contractions of physical activity which induces fat breakdown & burning
- The lack of muscle contraction will induce fat storage
- The essential fatty acids Omega-3 & 6 must be obtained through your diet as the body is unable to manufacture these essential fatty acids
- Fats are now recommended in our diets to induce health benefits
Next time: The ‘Lakeland 100’: Fuelling for a Ultra Marathon!
1– Lowery, L. (2013). Essentials of Sports Nutrition and Supplements: Fat. NJ, USA, Humana Press
2– Ryan. M. (2012) Sports Nutrition for Endurance Athletes (3rd Ed.). Colorado, USA, Velo Press
3– Venkatraman, J.T, Leddy, J and Pendergast, D. Dietary Fats and Immune Status in Athletes: Clinical Implications. Med. Sci. Sports Exerc. 32:389-395, (2000)