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This is a question that, even today, continues to be a source of debate and research and that is not totally clear.
Can you lose fat while gaining muscle mass?
If you ask an “old school” coach about this, he will tell you that of course YES, and he will do it with a resounding “I am sure of it because I have done it and anyone can do it”.
If you ask a professional a little more up-to-date and who cares about considering everything, he will answer you with a resounding NO, and I am almost certain that he will support his answer by saying that to gain muscle mass you have to be in a caloric surplus and to lose fat you have to be in deficit and therefore, it is something contradictory and impossible to do at the same time.
Questioning, doubting, having a critical spirit, personalizing, or qualifying is important since few things in our sector are 100% exact, and even what today we believe to be 100% true and that it is an immovable paradigm, tomorrow can be discarded and become one more myth.
In order not to get involved, let’s go to the topic in question. We have said that the answer to the question if you can gain muscle mass and lose fat at the same time, it DEPENDS.
We are going to turn to physiology again – of course!
A priori, we could say that the statement of the 2nd, who would have answered that it is NOT possible to do it because to gain muscle mass you have to be in surplus and to lose fat in deficit, is correct (although not entirely as we will see later). Anyone can not achieve these goals as they are contradictory in terms of calories, this a priori is so. However, there is a case where this may occur at the same time, and it is in overweight sedentary people who begin to perform physical activity.
Well yes, these individuals can do both at the same time. This is because these people have a low lean percentage and a high-fat percentage in their body composition, which is why they have insulin resistance. Insulin resistance in adipose tissue is because, as a result of being overweight, our adipocytes hypertrophy and therefore do not want to accumulate more fat inside. In order not to accumulate more fat inside, they become resistant to insulin in order not to take in more calories. In other words, insulin resistance, contrary to what one might think, is an action of our body to not capture nutrients, to avoid gaining weight. On the contrary, insulin sensitivity is a physiological process of our organs to capture calories, therefore gaining weight.
This insulin resistance and therefore the non-absorption of calories by fat cells, in overweight people, is the reason why these subjects have high blood glucose or triglycerides, which are what will produce long diseases such as diabetes II, atherosclerosis, etc.
If to this state of insulin resistance that the subject presents in adipocytes, we add the fact that a beginning subject gains muscle mass and strength very quickly, we have the complete equation. When a sedentary person receives a new stimulus in terms of workload, his skeletal muscle adapts physiologically very quickly, and as a consequence becomes bigger and stronger for the next time you submit him to that stimulus (training).
Training improves insulin sensitivity in myocytes since by performing intense physical activity, we will cause the emptying (complete or not, depending on the volume and intensity of it) of the glycogen stores.
Therefore we are in a situation where the sedentary overweight begins to train with adipocytes that resist continuing to grow (insulin resistance) and that when receiving a stimulus (training) improves insulin sensitivity in myocytes, causing them to capture calories to promote protein synthesis and for both getting stronger and adapting for the next workout.
This adaptation process happens to all of us
over time we become less and less sensitive to that stimulus. This explains why it tends to improve a lot at the beginning and we stagnate over time.
In sedentary but not overweight subjects who begin to train, this is not the case, since they do not have insulin resistance in adipocytes as they do not present excess fat. And in the case that we have mentioned of the sedentary with overweight, as they lose fat, their adipocytes will gain insulin sensitivity and instead of being reluctant to accumulate calories, the opposite will happen, they will welcome any excess calories to integrate it and store it. This partly explains why when we diet and we lose weight, our body stagnates and we cannot lose more and why we also regain the weight loss very quickly when we abandon the diet, what we call the rebound effect, although in these processes intervene many other factors also.
I hope I have solved the doubts regarding this issue, but as I said at the beginning of this article, everything DEPENDS and we should be attentive to what science brings us to continue clarifying concepts.