You can build muscle and burn fat at the same time
Can you build muscle and lose fat at the same time? Yes, you can!
Each of us has heard that there is no way to burn fat and build muscle. The most common reasons are:
  • To build muscle, you must store energy. To lose fat, you must burn energy.
  • When you are in an energy surplus, your body stores energy. When you are in a deficit, your body loses energy.
  • Therefore, you must be in energy surplus to gain muscle and in a deficit to lose fat.
Two of the points correspond to the law of thermodynamics, according to which energy must go somewhere. Building new fat or muscle cells requires energy and breaking them down releases energy.
To build muscle mass we need water, high amounts of protein, glycogen, and triglycerides.

So in practice, you must gain energy in energy surplus and lose energy in a deficit to burn fat and build muscle.
To prove this claim researchers at McMaster University took 40 males and put them on a 4-week diet and exercise program. Can some of them build muscle and burn fat at the same time.
They are separate in 2 groups - group 1 ate 1,2 g protein per kg body weight, group 2  ate 2,4 g protein per kg body weight. All of them ate 40% below maintenance calories to encourage fat loss. They also trained 6 days per week with weights and HIIT cardio.
The results are so interesting - all of those 40 men lost fat, but with small differences - group 1 burn around 4 kg., group 2 around 5 kg per 4 weeks.

Group 2 gained muscle growth around 2.5lbs of muscle, while group 2 didn't report muscle growth.
Burning fat and building muscle is possible as long as you take the right amount of protein, fat, and carbohydrates in your diet, as well as through a high volume of resistance and anaerobic exercise.