What You Should Know Before Fueling Up For A Marathon

on November 01, 2022

Elevate your training to the next level – get to know the nutrients your body needs to achieve your best performance.

During a 26mi/42km race, our body must use the two primary energy sources we have as reserves: carbohydrates and fat; this comes all on top of the loss of vitamins and minerals that our body uses, together with water.

More than a hundred years ago, it was a widespread belief that meat was the most essential part of an athlete’s diet, while today, the protagonists are pasta, bread, and rice.

Carbohydrates are our body’s primary fuel while working out. They are essential if we race or compete because of their genuine role in inciting muscle movements and being responsible for the proper operation of our central nervous system.

Carbohydrates are stored in our body as glycogens: 80-100 grams can be locked up in the liver and 300 – 900 grams in the skeletal muscle. These reserves can be depleted after a high-intensity exercise so replenishing them during your race will prevent you from hypoglycemia (a condition when your blood sugar level is lower than the standard range), which can result in dizziness, nausea, cold sweat and even in the loss of motor skills.

There are three main types of carbohydrates:

Simple sugars: such as fruit juices, fruits, sweetened cereals, jams, candies, chocolates, sugar, honey, and most sports drinks. 

These are digested and absorbed very quickly.

Starches: cereals, potatoes, bread, pasta, and rice, that are digested and absorbed quickly or slowly, depending on what they are accompanied with.           

Fiber: wholegrain cereals and bread, oatmeal, dry beans, peas, fruits, and vegetables. These are digested very slowly, and certain parts are not even digested or absorbed in our bodies.

Our body’s carbohydrate needs before, during, and after exercise will be discussed in detail in the next article. 

As far as fats are concerned, they are oxidized with carbohydrates. Suppose fats are becoming a predominant fuel during exercise. In that case, it depends on different factors such as the intensity of the exercise, the level of aerobic physical form, the diet, and the carbohydrate intake before or during the training. 

Increased fat oxidation is a direct result of increased energy. With higher-intensity exercises (greater than 75% VO2 max), fat oxidation is inhibited, and its relative and absolute speed of oxidation decreases. A study by Atchen et al (2002, 2003) – where they studied the relationship mentioned above between trained subjects and a wide range of exercise intensities – found that the highest rate of fat oxidation occurs between 62 and 63 VO2 max.

The effects of eating fat before or during exercise have been studied for a long time, so we can increase the presence of fatty acids and fat oxidation to reduce the chance of the catabolism of muscle glycogen. 

The fat our body gets from food provides our body with essential fatty acids that our body cannot produce, and these are needed for brain development, inflammation, and blood clotting control.

All fats are composed of saturated or unsaturated fatty acids, depending on the amount and type of fatty acid they contain.

On the one hand, saturated fats come from animal sources, such as butter, cheese, whole milk, fatty meats, and some plant foods, such as palm, coconut oils, etc. Since these could increase the cholesterol level in our body, they should be consumed with precaution and care.

On the other side, unsaturated fats help lower LDL cholesterol. Here we differentiate two main types: the monounsaturated ones, such as olive or canola oils, and the polyunsaturated ones, such as sunflower, corn, and soybean oils.

Finally, trans-fatty acids are harmful to health since their intake raises LDL and lowers HDL (good cholesterol). These can be found in hydrogenated oils such as hard butter and margarine.

Regarding protein consumption, most researchers agree that exercise increases protein oxidation to some extent. This increase is accompanied by nitrogen loss, causing a controversy about whether athletes should consume more protein than the non-active. It is a crucial observation that the more trained the person is, the lower his muscle catabolism will be, and therefore the lower his protein oxidation will be.

Protein intake will help the runner to repair and replace any damaged protein due to oxidative stress or mechanical damage in addition to remodeling adaptations produced by exercise and competition, as well as maintaining the optimal function of all the metabolic pathways of amino acids, which plays an essential role as intermediaries in the maintenance and increase in muscle mass. Furthermore, they contribute to optimal immune system functioning and physiological functions. 

We should consume high biological value proteins such as meat in general, let it be red (beef, veal) or white (chicken, turkey, fish); and whole eggs, dairy products (depending on tolerances), legumes (lentils, chickpeas, beans) if we are on a meat-free diet. It is recommended that long-distance runners consume between 1,2g-1,6g/kg/d while non-active people should eat 0,8g/kg/d. This also will depend on the needs and exercise performance.

It is also important to note that in addition to the macronutrients (carbohydrates, fats, proteins) our body uses, there are micronutrients divided into vitamins and minerals.

Within the vitamins are those with B complex, such as B12. These can be found in meat, fish, eggs, and milk; these vitamins contribute to the normal formation of red blood cells.

Among the minerals, we should mention iron, which tends to decrease in long-distance runners and can be found in meat, fish, and legumes.

Lastly, water also plays a significant role during and after exercise, ensuring that sports performance is not negatively impacted, which I will detail in another opportunity.

In conclusion, to the above explained, I recommend you consult with a professional specialized in sports nutrition who can accompany you during the preparation with the design of the nutrition and hydration plan tailored to individual needs and training.

Author: Jessica Drelichman

Master in Sports Nutrition

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