There is a very common misconception in society that intensity of exercise is not a huge factor in fat loss, as it is very well known that low intensity exercise has been shown to metabolise a high percentage of fat.
However this is not the case intensity of exercise plays a very big roll in weight loss, often at the start of exercise programmes walking is set as the best form of cardio for fat burning due to low activity levels of particpants but this is only the start. As a large number of overweight and sedentary individuals may not have the capacity to exercise at a higher intensity. This suggests that initiating their exercise regimen by walking is a safe and sensible practice. However, walking results in relatively small amounts of fat being oxidised due to the low metabolic demand of the exercise
In comparison, the exercise intensity that corresponds to the highest rate of fat use is around 60–70% of maximum oxygen uptake. This corresponds to about 70–80% of maximum heart rate and equates to a “moderate-to-hard” exercise intensity. Higher-intensity exercise burns more calories and increases thyroxine release, which increases cellular metabolism even during the recovery phase from exercise.
This suggests that even in sedentary individuals when exercising need to still keep progressing there intensity levels if they are targeting fat loss, this does not always mean doing more exercise or longer sessions but just increasing the output of exercise in each session.