Final answer:
During low-intensity exercise, the body mainly uses fatty acids from adipose tissue as an energy source. Adipose tissue contains the vast majority of the body's fat reserves in the form of triglycerides, making it the primary source for β-oxidation during extended low-intensity activities.
Step-by-step explanation:
During low-intensity exercise, the body primarily uses fatty acids as the main energy source.
Fatty acids are stored as triglycerides within adipose tissue, which comprises the majority of an organism's fat reserves. These fatty acids are liberated during exercise through the process of β-oxidation. Due to the nearly unlimited storage of fats in adipose tissue, these fats can fuel prolonged low-intensity activities. Even though the liver and muscles store some amount of fat, the vast majority is found in adipose tissue. Additionally, the liver is involved in the synthesis of fatty acids when there is an excess of glucose and ATP. These synthesized fatty acids are then stored back into adipose tissue.