Because in the initial exercise process, muscles will grow a little, even for women, because muscles are inexhaustible and discarded, and the density of muscles is very high. A small amount of muscle growth will not lead to the change of body shape, but it is likely to interact with the weight of fat consumed, and the body shape will change with the same or a slight increase.
If your figure has not changed, but you have gained weight, this situation should be the reason for your poor coordination of exercise or diet.