THE TRUTH ABOUT FATS
Fat (adipose tissue) plays a vital role in human function. Adipose tissue is found under the skin as an insulator, inside and between muscles, in cell membranes and surrounds the organs for protection. Fat-soluble vitamins A, D, E, and K are dependent on fat for absorption and transportation in the body. The primary function of fat is as an energy reserve for daily activities and when training within the aerobic threshold.
Fat as an energy source
The energy obtained from fat plays an important role for both high intensity and endurance sports. Fat serves as the primary fuel for low intensity and long duration activities such as marathons, triathlons, and cross-country skiing. In high intensity activity where carbohydrate is the primary fuel, fat is also necessary to fully release the available energy in the carbohydrates.
It’s important to bear in mind that although it is viable to use fats as an available energy source, its use is limited due to a number of factors:
It is digested slowly which extends the amount of time until the energy can be utilised. This also inhibits both the digestion and subsequent conversion of carbohydrates to glycogen and blood glucose.
Fat can contribute to gastrointestinal discomfort and indigestion during exercise
Stored fat in adipose tissue must be broken down and transported to the exercising muscle before the energy is readily available to it
To fully release the energy available in fat requires a greater amount of oxygen which can be a limiting factor and slows energy availability
Of the different types of fat – saturated, polyunsaturated, monounsaturated and trans-fats - some are highly beneficial for a number of reasons, while others have very negative effects.
The BAD fats
Saturated fats are of little benefit, especially to an athlete. They are in fact best avoided by all. Saturated fats are those that are solid at room temperature. Most are animal derivatives from meat and dairy products. This type of fat has a number of negative effects on the body including elevated blood cholesterol which can cause blockage in the arteries and lead to heart disease and hypertension. Certain types of cancers and strokes have also been linked to a high intake of saturated fat.
These fats also include some vegetable oils such as coconut or palm (which are not solid at room temperature). Coconut and palm oils also provide mono and polyunsaturated fats and phytosterols, providing various health benefits. Because they also have a medium trigylceride content they are easier to digest. They have been shown to be high in antioxidants, minimising the effects of ageing and providing nutrients for the neurological and nervous systems. As these are saturated it is important that they are consumed in moderation.
Trans-fats have a similar effect on blood cholesterol as saturated fat. Trans-fats are formed when liquid vegetable oil is converted into solid fat through the process of hydrogenation and are primarily produced to extend the shelf life of certain foods. Foods containing hydrogenated vegetable oil could also contain trans-fats (always read the label as they must be included in the list of ingredients). They are 100% man made processed fats and block the normal conversion of cholesterol in the liver, contributing to elevated cholesterol levels. They increase Low Density Lipoproteins (LDL - the bad cholesterol) and decrease High-Density Lipoproteins (HDL - the good cholesterol) causing an imbalance which can lead to coronary heart disease amongst other health issues. Trans-fats are often found in biscuits, cakes and fast food.
The GOOD fats
So if saturated and trans-fats are so bad, the athlete must source alternative fats. Unsaturated fats are split into two categories - Polyunsaturated and monounsaturated fats – and they provide a number of health benefits.
Polyunsaturated fats include the essential fatty acids (EFAs). It is important to include omega-3 (alpha-linolenic acid) and omega-6 (linoleic acid) essential polyunsaturated fatty acids in the diet because our bodies do not have the enzymes to create the necessary double bonds in the carbonyl group, which are the key identifiers of unsaturated fats. Thus, linoleic and linolenic fatty acids are termed ‘essential’.
Inadequate intake of EFAs can lead to a lowering in the efficiency of energy utilisation. This is obviously undesirable for an athlete. Fatty acids are an essential component of the Kreb’s cycle which releases the acids for metabolism by the beta-oxidation of fat. This increase will reduce the amount of carbohydrate being utilised and therefore increase endurance. However, a reduction in fatty acid oxidation will lead to an increase in the utilisation of carbohydrate as an energy source. It is therefore desirable for anyone training for an endurance event such as a marathon, to ensure sufficient consumption of EFAs.
EFAs are the precursor to a family of compounds called eicosanoids. These are metabolic regulators. Prostaglandins form part of this group and have been shown to be responsible for a range of functions. These include:
blood platelet aggregation - essential for the transportation of oxygen around the body
actions within the immune system – this is especially important for an athlete as high levels of physical activity can compromise the immune system
actions within the nervous system
body temperature increases
Alpha linolenic acid (ALA) is one of the omega-3 fatty acids termed as 'essential' because our bodies can convert ALA into others such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA is found primarily in dark green leafy vegetables, flaxseed oils and certain vegetable oils. EPA and DHA are found primarily in oily cold-water fish such as mackerel, herring, tuna (fresh not tinned) and salmon, plus linseed oil, rapeseed oil, soya beans and walnuts.
Unfortunately, plant sources of omega-3 fatty acids produce DHA and/or ALA and very little, if any EPA.
Foods rich in omega-6 include walnuts, sunflower seeds, peanuts and sunflower oil. Omega-6 is more readily available in the western diet, but many people in the UK have a deficiency of omega-3. You can incorporate these food types by sprinkling seeds on salads and vegetables.
There are no firm recommendations on the ratio of omega 3 to omega 6 fatty acids. However, it has been proposed that linoleic acid should make up a maximum of 3% of energy intake alpha-linolenic should comprise 1.3%.
Monounsaturated fats are liquid at room temperature (although some do change to solids when refrigerated). They have a number of health benefits and contribute to key processes within the body:
They often provide a good source of the fat soluble vitamins (A,D,E & K) and the presence of the fat itself allows the valuable vitamins to be absorbed within the body. These vitamins in turn help the absorption of key minerals such as calcium
Monounsaturated fats have also been shown to stabilise blood glucose levels. They improve a cell's sensitivity to insulin, and containing adiponetin, also improve that cell's ability to absorb the glucose from the blood supply
Studies suggest that consuming monounsaturated fats can reduce LDL cholesterol and increase HDL cholesterol (as touched upon above)
Many studies support the theory that the flavonoids, polyphenols and squalene found in olive oil all help protect you from both breast and colon cancers
For arthritis sufferers, their anti-inflammatory properties are of great interest
Rich sources of monounsaturated fats include olive and rapeseed oils, almonds, brazil nuts, pumpkin and sesame seeds and avocados.
So in summary, fat is not the enemy it is portrayed to be. Instead it has an essential role to play in the body's processes and has many health benefits, not least helping to protect from chronic diseases. As with all aspects of nutrition, it's all about balance and maintaining an equilibrium. A fat free diet is depriving your body of an essential macronutrient that it was designed to process. Too much of the wrong types of fat has far reaching consequences, but make the right fat choices and you'll reap the benefits.