During an ultramarathon, the body primarily burns carbohydrates, which are the body's preferred source of quick energy. However, the body's carbohydrate stores (glycogen) are limited and can become depleted, especially during prolonged exercise such as an ultramarathon. Once the glycogen stores have been used up, the body switches to burning fat for energy. This is why ultra runners often consume high-fat foods and supplements during the race to maintain their energy levels.
It's important to note that the body also needs to stay hydrated during an ultramarathon, as dehydration can lead to decreased performance and even serious health issues. Ultra runners often carry water and electrolyte supplements with them during the race to maintain proper hydration levels.
Carb loading or fat loading before a race ?
When you consume high-fat foods, it usually takes some time for your body to break down and digest the fats and then convert them into energy that can be used for exercise. The exact amount of time it takes depends on the type of fat consumed and other factors such as metabolism, activity level, and the timing of the fat intake in relation to the exercise.
In general, it can take anywhere from a few hours to several days for the body to start fully utilizing a high-fat diet for exercise. Some ultra runners follow a high-fat, low-carbohydrate diet for weeks or even months before a race to train their bodies to use fat as their primary fuel source.
It's important to note that while high-fat diets can provide sustained energy for endurance activities like ultramarathons, they may not be ideal for all athletes. Each person's body is different, and some people may not tolerate high-fat diets as well as others. It's always a good idea to consult with a healthcare professional or a registered dietitian before making any significant changes to your diet.
The amount of carbohydrates needed to spare the body's fat stores during endurance exercise depends on several factors, including body weight, exercise intensity and duration, and individual metabolism. A general rule of thumb is that endurance athletes should consume approximately 30-60 grams of carbohydrates per hour of exercise to maintain performance levels, with the aim of reducing the reliance on fat as a fuel source.
However, it's important to note that the amount of carbohydrates needed can vary significantly from person to person. Some ultra runners may find that they need to consume more carbohydrates during a race to maintain energy levels, while others may be able to tolerate less. It's important to experiment with different nutrition strategies during training runs and races to determine what works best for your body.
In addition to carbohydrates, it's also important to maintain proper hydration levels and electrolyte balance during endurance exercise, as these factors can also impact energy levels and athletic performance.
To Completely restore/ refuel your glucose levels.
To allow for maximal exogenous glucose oxidation rates (1g-min)
A well-trained endurance athletes competing longer than 2.5 h can metabolize carbohydrate up to 108 g·h⁻¹ (~1.5-1.8 g·min⁻¹) provided that multiple transportable carbohydrates are ingested
So you only need between 90- 108g of carbs per hour. And you will be able to burn enough energy for the hour.
So what will you do next? Train on a high fat diet and review how you feel or carry on eating crap load of carbs before and during each race. 1g of carbs or protein turns into the Cals of energy. Fat is 9cals per g.
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