At what percentage of VO2 max does the greatest amount of fat "burn" occur?

The greatest amount of fat burning typically occurs at around 65 percent of VO2 max. This phenomenon is rooted in how the body utilizes fuel sources during exercise intensity. At lower levels of intensity, the body tends to rely more on fat as its primary source of energy. As exercise intensity increases, there is a shift where carbohydrates become the dominant fuel source.

At approximately 65 percent of VO2 max, the body is efficiently utilizing both fat and carbohydrates, but it still maintains a notable level of fat oxidation. This ideal balance means that the body can utilize a significant portion of fat while being able to sustain exercise and performance levels. Higher intensities, such as those above 75 percent, generally reduce the relative percentage of fat being burned, despite total caloric expenditure potentially increasing. This understanding is critical for runners and coaches who aim to optimize fat utilization during training and races.