During the summer months this is a question we are often asked as people prepare to take well-earned holidays…
It is impossible for muscle to turn to fat and vice versa. Lets take an example of someone who is training 4/5 times per week and they have a fair amount of lean muscle tissue within their body. Their calorie consumption will ideally match their training needs. If that athlete then stops training due to injury or holiday etc….the metabolism will start to slow down, meaning the body is less efficient at burning calories consumed. He/she may start to lose lean muscle tissue. If the calorie intake is not adjusted accordingly to suit the individuals activity levels then the athlete will indeed see some increase in overall body fat %.
On the flip side, it is also impossible to turn fat into muscle. When an athlete starts to exercise they start to burn fat by working different energy systems in the body and working at mixed intensities.
As the muscles are pushed to fatigue and beyond there are micro tears that appear in the muscles. As the muscle fibre tears start to grow back and repair, they grow back bigger and stronger this is what gives us a defined muscle or a “toned” muscle. So in short you can burn fat and build muscle but they will never turn into each other.