Hi all
Just discovered this recent study which is getting me worried about my gym progress:
A small study of 36 people found that a normal diet led to more weight loss and no loss of muscle mass, however intermittent fasting led to muscle loss
They tested three diets:
intermittent fasting: alternate between one day of fasting and one day where you eat 50% more calories
normal calories restriction diet: eat 25% less calories than normal every day (the total number of calories is the same as in the first diet)
intermittent fasting without calorie restriction: Alternate between one day of fasting and one day where you eat 100% more calories than usual
Participants who followed the diet 2) for three weeks lost an average of 1.9 kg, or 4.2 lbs. Those on the 1) diet lost 1.6 kg, or 3.5 lbs. The third group did not lose a significant amount of weight.
More striking than the overall difference in weight loss was the type of weight loss. The normal diet group lost their weight almost entirely by shedding fat. But the fasting diet group lost about half of their weight in fat and half in muscle mass
What are your thoughts on this?potential loss of muscle mass
It makes sense I think - all 3 of these examples are participants who are going in and out of a weak ketogenic state, which from what I remember does catabolise muscle for a brief period (unfortunately I think it’s the period they repeatedly enter in and out of).
Will need someone more knowledgable to chime in, but prolonged fasting avoids this as you pass that state and go deep into ketosis where your energy comes almost solely from fat.
Think the stages is something like:
Carb
Carb/Fat/Protein (from muscle)
Fat/Protein (from muscle)
Fat
That all happens pretty fast, within about 36 hours you’re in the deep ketosis almost pure fat burning stage. So if you just stay there, you’re good and avoid that muscle loss phase. Going back in and out is the issue - I’m assuming as it’s logical. But I’d really prefer to hear someone like Fung explain it out and discuss the study itself.
Maybe much later where you body runs lower on resources it will turn back to Protein (from muscle) again of course. And this is where fasting on lower body fat is a different game I’d guess.
If anyone does see a good deep dive on that study please do link it!
That study is flawed as none of the groups were monitored for daily weight lifting.
You need to weight lift daily while on IF to mitigate muscle loss. I always say that The body has a use it or lose it principle when it comes to the brain and muscle mass. I do IF every day and I’ve maintained my lifts and muscle mass easily. However, There is a threshold as to when muscle mass begins to occur at an accelerated rate. From my personal experience and from reading studies, Reddit fasting testimonials, etc that threshold is somewhere between 60-72 hours of fasting depending on age and genetics.