Today, we explore why intermittent fasting is potentially sub-optimal for muscle growth, remodelling and recovery.
Intermittent fasting (IF) comes in many shapes and forms. Whether that’s your classic 16:8 fast, 24h or 36h fast. Either way, the dietary approach causes you to restrict your meals to smaller eating windows within a day.
For many, IF allows individuals to better manage their calorie intake, and in most cases, allows them to seamlessly create a calorie deficit to drop body fat.
From a body fat centric perspective, IF is not superior for fat loss when calories are equal.
From a muscle centric perspective, IF is deemed to be sub-optimal for building muscle when calories are equal.
A review paper by Williamson and Moore (2021) argues the point that the frequency of which you eat protein on a daily basis will impact how much muscle is created by the end of each day.
Your muscle is in a constant state of turnover – breakdown (Muscle protein breakdown – MPB) and growth (Muscle protein synthesis – MPS). Therefore, muscle is built when MPS exceeds rate of MPB…and therefore you’re in a state of positive protein balance.
The stimulus from weight training provides the most robust response for MPS (i.e. the primary driver for growth). Protein intake is second to this. More so, the amount of protein eaten at every meal.
Once adequate protein is consumed each meal (~0.4-0.5g/kg), MPS is stimulated and remains ‘switched on’ for 3-5 hours (depending on the size of the meal).
If inadequate, or no protein is consumed, then MPS will not be stimulated…and therefore MPB will most likely exceed MPS and you’ll spend more time in net negative protein balance (graph B & C – light grey shaded area) .
Knowing this, the current recommendations are to evenly distribute protein throughout the day to capitalise your time spent in net positive protein balance (graph D – dark grey shaded area).
If you were to eat higher amounts of protein per meal to play catch up, i.e. miss breakfast and consume larger protein portions at lunch and dinners, the additional protein will become oxidised (unused for muscle growth) and most likely will not further support MPS (OX – dotted line on graph).
Therefore, IF may support body fat by helping to create a calorie deficit. But, to maximise daily protein efficiency and maximise muscle growth, eating the correct amount of protein, and not skipping your protein at meal time is certainly recommended.