This is one of the biggest questions in fitness and bodybuilding, and one with very contradicting answers. On one hand, we have people saying that it’s impossible to have both at the same time because they require your body to be in very different states. On the other hand, we have people saying that you can do it if you train right.
Let’s answer that question once and for all, and find out if we can actually build muscle while losing fat. To do that, we have to understand what is it exactly that happens in our body when the muscle grows.
As a general rule, it’s often said that your body needs to be in caloric surplus for the muscles to grow. It’s a simple rule that basically says you have to eat more to get bigger. The problem with that is that in order to lose fat you have to be in caloric deficit, that is to eat less. So following this advice it’s seemingly impossible to have the two at the same time, however the devil is in the details.
How Muscles Grow
Muscles grow in the process of healing during recovery. During your workout, you break your muscles and micro tears appear in muscle fibers which then heal by growing scar tissue – they get bigger. To heal, your body needs quality proteins as tissue building element. Since muscles are 70% protein, you need that protein to come from food.
First, you have to understand that not all calories are equal and you can be in caloric surplus but don’t gain any muscle because those are the wrong kinds of calories. You need to get them from protein for muscle protein synthesis, while complex carbs and healthy fats are used for energy.
So if you break your muscles and provide the required protein to rebuild, the muscles will grow. However, if there’s an overall caloric surplus, your body will not burn the fat. So the question becomes, can your body grow muscle if there’s enough protein but you still have the caloric deficit necessary to burn fat?
Your body’s capacity to recover after a workout and to grow muscle is really determined by the nitrogen balance which is only partly affected by caloric balance. Nitrogen is the compound unique to protein among micronutrients, so a positive balance in your body means there’s a surplus specifically in protein and your body is in the anabolic state capable to rebuild. So while the general rule says the caloric surplus is the key to muscle growth, actually it’s the nitrogen balance, and you can have it positive while in overall caloric deficit. This is good news for us.
There’s one caveat, though. As mentioned earlier, quality carbs and fats are necessary for energy to support protein synthesis. If there’s a lack of carbs and fats, protein is used for energy and the nitrogen balance drops. In other words caloric deficit can affect muscle growth negatively, but it’s important to note that it doesn’t prevent it completely (unless taken to the extreme).
Calories Stored in Body Fat
But here’s another bit of good news. Your body stores fat for a reason. It’s the surplus of calories to be used for energy when needed, so burning fat actually means using those stored calories. While they are not readily available as consumed calories, body fat still provide extra energy in caloric deficit, energy that can be used to support protein synthesis.
So to conclude, the answer to the question whether you can burn fat and build muscle at the same time is yes, you can. Granted muscle growth will not be as effective as in caloric surplus, you can cut the calories significantly and still gain muscle (so long as you’re not drastic about it).