Let me start off by saying that the above statement does not necessarily apply to everyone but if you do a lot of cardio and can’t seem to drop those pounds, you may want to consider it.
The statement is based on a few facts:
- The body adapts to exercise very quickly by becoming more efficient to the physical demands – if you do the same workout two times in a row your body will be about 20% more efficient the second time.
- The body adapts to the energy system demands of a workout very quickly meaning that it will be more efficient at delivering the energy needed to perform the same workout next time.
- The body overcompensates to the demands of a workout to ensure that there is more than enough strength and energy to get it through the same workout next time.
Here is the problem with steady-state cardio as it deals with long term fat loss – your body is so good at adjusting to any repeating physical demands that there is a diminishing marginal caloric-cost to each workout. When you are working in the fat burning zone (between 50-65% of your heart rate max), your body adjusts to these workouts to ensure that there is enough energy to fuel them. Given that they rely more on fat utilization for fuel, the body adapts by increasing the amount of fat that is available. The consequence to this adaption is an increase in fat storage.
This isn’t a big deal initially as you are able to increase the amount of work that you do to stay ahead of the increased energy (fat) storage but at some point very early on, the body catches up and begins to store more fat than you are able to burn off (remember 1 and 2 above). At this point, steady-state cardio stops having a fat loss effect and starts having a fat maintaining effect. When one will achieve this point depends on a number of factors but I would estimate that most people will achieve it after about 2-3 months.
Examples would include the over-weight aerobics instructor, marathon runner or tri-athlete because these individuals spend a lot of time with elevated heart rates and have adapted to the physical demands of the activity. While their cardiovascular health is superb, their body rely so heavily on fat metabolism for energy that they store fat very effectively to allow for the sustained effort that their sports demand.
Long-term fat loss is best achieved through resistance and strength training to increase lean muscle mass, and moderate amounts of high intensity interval training (HIIT) to tax all energy systems. HIIT is best described as periods of increasing work effort followed by recovery phases. A good HIIT workout will see you heart rate modulate between 60% of you max to 95% of your max but will never stay at one level for more than a few minutes.