Fat loss is probably the most universally desired outcome from training, shredding away body fat and revealing chiselled abs and lean, defined muscles. But very often we hear trainers using the terms ‘fat loss’ and ‘fat burning’ being used interchangeably which can lead to a lot of confusion.
When an individual or coach talks about fat loss, they should be referring to the overall process of an individual losing fat, looked at over a longer period of time; usually over the course of an entire day to multiple weeks or months.
When talking about fat burning (to be scientifically correct, fat oxidation), they should be referring to the process of the body using fat for energy during an activity (and sometimes during the subsequent recovery); this will be anywhere from a few minutes to 48 hours.
So why is it important to get the terminology right?
Because increased fat burning does not mean increased fat loss.
Fat burning is constantly occurring in the body. It is the primary source of fuel for energy at rest and lower intensities of exercise, the maximum amount being burnt typically peaking between 50-80% of maximum heart rate. This point – commonly referred to as Fat Max – varies greatly from individual in how much fat is being utilised and at what percentage of maximum heart rate it occurs due to genetic factors and training adaptations.
Conversely exercise at high heart rates (in excess of 80% max heart rate) the body utilises glucose almost exclusively as its energy source; but in recent years the popularisation of HIIT (High Intensity Interval Training) has shown that you can lose body fat with this training method.
So while it seems LISS burns more fat than HIIT, they both achieve similar fat loss when used as part of a structured training and diet plan. So why is this the case?
Overall fat loss can only be achieved by creating an extended period of caloric deficit (daily or weekly, depending on diet periodisation) regardless of how much fat burning the body does. Without a caloric deficit, the body will have surplus energy to its needs and will store this (regardless of whether the calories are from protein, carbs or fat) as body fat. Under the right conditions of a caloric surplus the body can also build new muscle tissue, although it cannot channel excess energy exclusively to muscle gain – fat gain is inevitable and the amount of fat gained will increase faster (muscle gain plateaus) as the calorie surplus becomes larger.
Other than being in a calorie deficit, is there anything else that can speed up fat loss?
Some supplements (caffeine and green tea) are well documented as having small positive effects on fat loss by increasing fat burning; preferentially metabolising fat to fill the energy gap created by the calorie deficit. Although some other supplements claim to have an effect on fat metabolism, they may not increase fat burning. This is because fat metabolism is a complex process with many steps and increasing the speed of one step does not guarantee the overall rate will increase. Imagine the cells in your body are a factory with workers inside (mitochondria), converting fat to energy – increasing the amount of fat arriving at the factories will not increase the amount of fat burnt if the factories are already operating at full capacity! The step that controls the overall rate of a process is known as the ‘rate limiting step’ and increasing this is the only way to speed up a process. We cannot tell what the rate limiting step is in our own fat metabolism is, so unless a supplement can speed up all the processes, it cannot guarantee it will increase fat burning!
The take home message from this is; don’t get confused by ‘experts’ who talk about when and how you should exercise to increase fat burning. Focus on your overall fat loss by creating a sensible calorie deficit through a combination of diet and training – and although there is a small number of cheap readily available supplements that can help increase fat burning, always be sceptical of new products that claim to increase fat burning or fat loss.