1400 years ago, the slow conversion of fats to energy was not understood, yet the Quran mentions this process. Today, we know that fats are the slowest source of energy for the body.

Fats serve as both an energy source and a store of energy in the body. When metabolized, fats release approximately 9 calories (37 kJ) per gram. However, the conversion of fats to usable energy is a slower process compared to carbohydrates, which are more readily available for quick bursts of energy. Fats are broken down into fatty acids and glycerol. Glycerol can be converted into glucose by the liver and used as energy. However, for quick activities like sprints, the body prefers to use carbohydrates, which are faster to metabolize. Fats, on the other hand, are burned during prolonged activities like marathons or long-distance travel, where endurance is key. This process is much slower and occurs over extended periods.

In Surah 22:27, the Quran talks about long journeys and the animals that travel over great distances:

The Arabic word "Damer" (ضَامِرٍ) means "skinny" or "thin," describing animals that become emaciated after traveling long distances. This reference to animals becoming thin is not just about the physical appearance but is an indication of the endurance required for such long journeys, which leads to fat burning. In short, for short distances (like walking for a few minutes), the body does not burn fat effectively, but for long-distance activities, such as traveling long distances on foot or by animal, fat stores are used as energy.

1400 years ago, people did not have the modern understanding of metabolism and fat burning. Despite this, the Quran described the effects of long endurance activities—such as traveling long distances on foot or with animals—and how these activities lead to the burning of fats. The fact that this principle is mentioned in the Quran, long before it was scientifically understood, suggests a deeper knowledge that was far ahead of its time.