Because in the first few weeks of exercise, you will lose some fat, but at the same time, your muscles are also increasing. If you do strength exercises or resistance exercises, muscle mass, including muscle content, will increase faster. Therefore, when the density of muscle fiber increases, the content and weight of muscle increase accordingly.
At the same weight, the volume of muscle is smaller than that of fat. Generally, the volume ratio of muscle to fat is at least 1: 3. Therefore, before losing weight, the circumference of waist and abdomen may be reduced by several centimeters. After about 4 weeks of exercise, when your body adapts to strength exercises or resistance exercises, the quality of muscles, including the growth rate of muscles, will slow down, and then the pointer on the weighing scale will slowly move down.