Utilize lipids as an energy source to improve endurance! How mitochondria work and how to increase them

The main sources of energy during exercise are carbohydrates (glycogen) and lipids

Our bodies use the energy contained in the carbohydrates and lipids we ingest every day from our meals to maintain vital functions and perform exercise.

Differences in energy sources depending on exercise intensity

Figure 1

Figure 1 shows how the energy sources used in the body differ depending on how hard you exercise.¹⁾.
When you do light exercise like walking, your body mainly uses fatty acids, which are a type of lipid. However, when you do strenuous exercise that makes you out of breath, your body uses carbohydrates (glycogen) stored in your muscles as your main source of energy.

Glycogen stores

How much carbohydrates and lipids, which are sources of energy, are there in the body?

Carbohydrates taken in from food are stored as glycogen in muscles and the liver. The amount of glycogen varies from person to person depending on muscle mass, but even athletes, who are said to have more glycogen than the average person, can only store about 2,000 kcal. It is said that about 2,500 kcal of energy is needed to run a full marathon. Therefore, if you only use carbohydrates, you will run out of carbohydrates midway through the marathon and will not be able to run any further.

lipid storage

As you know, lipids are stored as fat, but an average adult weighing 60 kg with a body fat percentage of 15% will have about 9 kg stored, providing about 65,000 kcal of energy (calculated at 7.2 kcal per gram), which is more than 30 times the amount of energy stored in glycogen.

In other words, if you can utilize the lipids in your body as well as the carbohydrates during exercise, you will not run out of energy and your endurance may improve.

1) Romijn JA, Am J Physiol. 1993 Sep;265 (3 Pt 1): E380-91.

Mitochondrial function is important for using carbohydrates and lipids

So how does the body use carbohydrates and lipids?

We have explained that carbohydrates and lipids are used as energy sources, but in the body, carbohydrates and lipids are not used as they are, but are converted into a substance called ATP (adenosine triphosphate). The organelles inside cells called "mitochondria" act as factories that produce this ATP from carbohydrates and lipids.²⁾(Figure 2)

Figure 2

²⁾ Turcotte LP, Am J Physiol. 1992 Jun; 262 (6 Pt 1): E791-9.

Boosting mitochondrial function improves endurance

Mitochondria in muscles grow larger and increase in number through training, like that of a marathon runner. Increasing the number of mitochondria in muscles in this way allows the body to use more lipids as an energy source during exercise. By using lipids as the main energy source during exercise, the body can conserve (preserve) the limited amount of glycogen in its body. (Figure 3)

Figure 3

If you want to improve your endurance and perform better, you need to increase the number of mitochondria in your muscles. If you can use lipids as an energy source in your body, you can prevent carbohydrates from running out and you can continue exercising for longer. In other words, your endurance will improve.

Utilizing carbohydrates and lipids as an energy source to improve endurance – The role of mitochondria

The following points are important for making effective use of the body's energy sources and increasing endurance.

• -Carbohydrates and lipids consumed in the diet are used as energy sources
• ・When you do hard exercise, carbohydrates are mainly used and you become tired.
• The amount of energy stored in the body from carbohydrates is small, while the amount of energy stored in lipids is large.
• ・The function of muscle mitochondria is important in order to use carbohydrates and lipids
• Increasing the number of mitochondria in muscles allows them to better utilize lipids as an energy source
• ・Increased use of lipids helps to conserve carbohydrates, which helps to increase endurance

Increasing the number of mitochondria in your muscles allows you to utilize more lipids in your body. Let's look at scientific methods to increase your endurance according to your exercise goals in order to achieve optimal performance.

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<Supervisor>Shin Terada

Completed the doctoral program at the Graduate School of Human Sciences, Waseda University (PhD in Human Sciences). After working as a PD special researcher at the Japan Society for the Promotion of Science, a researcher at the University of Washington School of Medicine, a researcher at Sankyo Co., Ltd., a lecturer at the Waseda University Institute for Advanced Science and Health Care, and director at the Central Research Institute of Nisshin Oillio Group Co., Ltd., he will become a professor at the Graduate School of Arts and Sciences, the University of Tokyo, in 2023.