It is mentioned in Barbell Medicine videos and articles that it is not possible to lose fat and gain muscle at the same time. (excluding very obese people)
Still some people suggest that this is possible but the amount of gained muscle mass is compromised which makes sense in a way. If stress (weight training) is applied to muscles, it needs to grow and/or get stronger in other way to adapt to the stress. Because of this, additional amount of protein and energy is needed and the energy can be taken from the energy storage (body fat). Therefore, muscle growth in a calorie deficit state should be possible given that protein intake is high enough. What exactly prevents this from happening?
P.S. I don’t know s**t about any medical stuff and sorry for possible spelling mistakes, I’m from Finland.
We say that most folks who are neither undertrained or overfat won’t be able to lose appreciable amounts of body fat whilst gaining appreciable amounts of muscle.
There are no protein stores in body fat and while it is true that body fat is an energy source for various metabolic functions, this doesn’t increase the amount of muscle mass appreciably or even participate in muscle anabolism to a significant effect.
Muscle anabolism relies primarily on essential amino acids (dietary) and training. However, if the net metabolic climate of the body is to be losing weight, then it is very difficult to have a net anabolic state in one system of the body unless someone is untrained or very sensitive to training (generates a high response to training) or very overweight.