However, the distribution of human body fat is controlled by the body system. Being thin is a systematic process, and you can't just lose weight in a certain part (all those claims that you practice losing weight are unscientific).
The stomach is easy to gain weight, because it is easy to accumulate fat (fat accumulates under the skin of the stomach, in fact, a lot of fat is stored between the internal organs of the stomach), and where it is easy to accumulate fat, the order of reducing fat is backward (where there is the most fat, it is also the least easy to reduce fat), but because there is more fat accumulated there, the effect of reducing fat is also the most obvious (there may be a few pounds here, and the change of waist and abdomen circumference is relative to others)
However, losing weight depends not only on exercise, but also on diet and work and rest.
In addition, if you want to tighten your abdomen, you'd better add some abdominal exercises besides running! Because muscles are stronger, targeted exercise is more immediate.