So, we’ve reached the final part of the fat burning process, oxidation. Before I continue it’s important to note that not all fatty acids that go through the transportation and mobilisation phases are oxidised and used as energy. The reason for this is simple, without the “energy deficit” the mobilised fat will just be stored. Throughout the day we go through various stages of fat loss and fat storage, it’s not an either-or process and as noted in the previous blog, the process is heavily dictated by the presence of insulin.
Oxidation is the final process that occurs when the long chain fatty acids with acetyl form Acetyle-CoA. These are then oxidised (reduced) to CO2 in the various stages of the citric acid cycle. So where does the energy come from? The electrons derived from the first two stages are passed onto O2 and it is this oxidative phosphorylation is where we derive the energy needed for the resynthesises of ATP (chemical energy). Again, it's important to note that not all fatty acids are reduced this way as some are stored again, it’s all dependent on the energy deficit.
Low Carb/Ketogenic diets and Fat Loss
Ketogenic diets are hugely popular right now. But how and why does this effect fat burning? How does the physiology of it work? When we go on a low carb or ketogenic diet the percentage of fats in the diet notably increase whilst carbohydrates decrease. Once the increased amount of fats in the diet are digested the amount of fatty acids in the bloodstream increases. This leads to a considerable increase in a process called re-esterfication aka fats entering the cell. Now although fats leaving the cell (lipolysis) has increased as has the amount entering the cell. So realistically the end product is the same.
So, why and how do people lose weight? Same as every other diet. It is ultimately down to calorie balance and exercise. When people change diets, it’s usually coupled with increased exercise aka energy output or change in training strategy. If the extra fatty acids in the bloodstream brought about by a low carb diet aren’t oxidised for energy, they are put back in the cell. We burn more fat yes but catch 22 is we also store more fat and become efficient at doing so. This is the potential problem with not just low carb/ketogenic diets, but any diet that is devoid of any nutrient. In the case of low carbs, the problem is that it’s hypothesised that mechanically we become more efficient at using the excessive substrates as fuel over time, but the paradigm we have is that if we persist at a low carb diet we become inefficient at the oxidation of glucose and thus efficient at storage. If we persist with a high carb diet, we become inefficient as the oxidation of fat and efficient at the storage. It’s all about that energy deficit.
Without an energy deficit neither approach will result in a higher net fat loss than gain. Intra-personal efficiency must be a consideration, I’ve said it numerous times in my blogs this will evolve from a mechanistic standpoint that’s heavily dependent upon the current dietary habits and finding what works for you by observing the physical compositional changes when altering carb/protein/fat levels.
Our Recent Posts
Age old question and probably one of the main reasons people abandon their diet and workout routines. Trying to explain to people that weight loss SHO...
How Often Should You Measurements To Track Progress?
September 9, 2019
Just a reminder, calorie calculators and CICO aren’t the same.
Whilst many people use calorie calculators to estimate their energy needs and adjust the...
Calorie calculators - cals in vs out aren’t the same
August 2, 2019
This is probably one of the weirdest issues in the fitness industry to date. I've seen trainers post massive facebook/insta blurbs and charge clients...