THE benefits of fasting are manifold, going beyond just weight loss. One of the effects of intermittent fasting is reduced calorie intake and hence reduction of body weight.
Intermittent fasting also leads to improved metabolic health, increased energy and cognitive performance and autophagy (a natural body rejuvenation process).
But how do we fast without losing muscle mass? This would require an understanding of muscle cell physiology.
Net muscle mass is balanced between anabolism and catabolism. Anabolism means building, whereas catabolism refers to breaking down. Our brain cells prefer glucose over fat as a source of energy.
Therefore, in a fasting state, the liver triggers a process called gluconeogenesis, to generate glucose from mainly proteins in order for the brain to use.
Hence, with prolonged fasting (five days or more), we see a decline in muscle mass, as muscle is the most readily available source of protein (to be converted to glucose via liver gluconeogenesis) in our body.
On the other hand, muscle anabolism takes place via mTOR activation which leads to muscle protein synthesis, increasing muscle mass and strength.
This can be activated by physical exertion of muscles (resistance training) and protein (especially the amino acid leucine). Both exercise and protein intake activate mTOR and hence muscle anabolism for about six hours, and in a dose dependent manner, up till a certain limit.
EAT RIGHT
The first point to reduce muscle loss during fasting is to have adequate intake of protein in our diet. Animal sources of protein are the best quality.
In general, the optimal amount of daily protein intake tends to be somewhere between 1.0-1.5g/kg of lean body weight. Therefore, for a person with a 60kg lean body mass, the daily protein intake should be between 60-90g.
There is also a limit on protein absorption per meal, as proteins have to be digested and absorbed as amino acids into our intestinal lining cells through specific transporters and moved out of intestinal lining cells on the other side for circulation in the bloodstream.
It is estimated that we can only absorb a maximum of 30g of protein in one sitting. To further reduce muscle catabolism during fasting, we can activate mTOR (the anabolic switch of our cells, including the muscle cells) via physical activities like resistance exercises.
Body weight resistance exercises are convenient, easy to follow and safe.
Squats, lounges and push-ups can be performed with various degrees of difficulty and intensity, with more focus on our torso and lower limbs as those are categorised as larger muscle groups.
Be sure to also time your exercises around meal times to further activate the mTOR switch in order to build muscle mass. There are a myriad of benefits with fasting. With a little more understanding of our body physiology, we can reap these benefits without the potential issue of muscle mass loss.
Take note of your daily protein intake, be aware of the limit of protein absorption per meal and engage in some form of resistance exercise around your meal time in order to reduce muscle mass reduction during your intermittent fasting period.
*The writer is a consultant orthopaedic and spine surgeon at Alty Orthopaedic Hospital.
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