Your body is covered with skin which has a layer of subcutaneous fat which covers.
If you have a high percentage of body fat which is covering your body you will not show muscle tone.
If you have a body fat percentage which is higher than average you have to lose some your body fat in order to improve your muscle tone.
If you have a body fat percentage which is lower than average or lean, you have to build muscle to increase your muscle tone.
There are no secrets about which exercises or diets improve muscle tone just the plain, simple science behind body composition. If you burn more calories than you consume you will gain body mass, if you burn fewer calories than you consume you will lose body mass.